TPA uses [Puppet](https://puppet.com/) to manage all servers it operates. It handles
most of the configuration management of the base operating system and
some services. It is *not* designed to handle ad-hoc tasks, for which
we favor the use of [fabric](howto/fabric).

[[_TOC_]]

# Tutorial

This page is long! This first section hopes to get
you running with a simple task quickly.

## Adding an "message of the day" (motd) on a server

To post announcements to shell users of a servers, it might be a good
idea to post a "message of the day" (`/etc/motd`) that will show up on
login. Good examples are known issues, maintenance windows, or service
retirements.

This change should be fairly inoffensive because it should affect only
a single server, and only the `motd`, so the worst that can happen
here is a silly motd gets displayed (or nothing at all).

Here is how to make the change:

 1. To any change on the Puppet server, you will first need to clone
    the git repository:

        git clone pauli.torproject.org:/srv/puppet.torproject.org/git/tor-puppet

    This needs to be only done once.

 2. the messages are managed by the `motd` module, but to easily add
    an "extra" entry, you should had to the Hiera data storage for the
    specific host you want to modify. Let's say you want to add a
    `motd` on `perdulce`, the current `people.torproject.org`
    server. The file you will need to change (or create!) is
    `hiera/nodes/perdulce.torproject.org.yaml`:

        $EDITOR hiera/nodes/perdulce.torproject.org.yaml

 3. Hiera stores data in YAML. So you need to create a little YAML
    snippet, like this:

        motd::extra: |
           Hello world!

 4. Then you can commit this and *push*:

        git commit -m"add a nice friendly message to the motd" && git push

 5. Then you should login to the host and make sure the code applies
    correctly, in dry-run mode:

        ssh -tt perdulce.torproject.org sudo puppet agent -t --noop

 6. If that works, you can do it for real:

        ssh -tt perdulce.torproject.org sudo puppet agent -t

On next login, you should see your friendly new message. Do not forget
to revert the change!

The next tutorial is about a more elaborate change, performed on
multiple servers.

## Adding an IP address to the global allow list

In this tutorial, we will add an IP address to the global allow list,
on all firewalls on all machines. This is a big deal! It will allow
that IP address to access the SSH servers on all boxes and more. This
should be an **static** IP address on a trusted network.

If you have never used Puppet before or are nervous at all
about making such a change, it is a good idea to have a more
experienced sysadmin nearby to help you. They can
also confirm this tutorial is what is actually needed.

 1. To any change on the Puppet server, you will first need to clone
    the git repository:

        git clone pauli.torproject.org:/srv/puppet.torproject.org/git/tor-puppet

    This needs to be only done once.

 2. The firewall rules are defined in the `ferm` module, which lives
    in `modules/ferm`. The file you specifically need to change is
    `modules/ferm/templates/defs.conf.erb`, so open that in your
    editor of choice:

        $EDITOR modules/ferm/templates/defs.conf.erb

 3. The code you are looking for is `ADMIN_IPS`. Add a `@def` for your
    IP address and add the new macro to the `ADMIN_IPS` macro. When
    you exit your editor, git should show you a diff that looks
    something like this:

        --- a/modules/ferm/templates/defs.conf.erb
        +++ b/modules/ferm/templates/defs.conf.erb
        @@ -77,7 +77,10 @@ def $TPO_NET = (<%= networks.join(' ') %>);
         @def $linus   = ();
         @def $linus   = ($linus 193.10.5.2/32); # kcmp@adbc
         @def $linus   = ($linus 2001:6b0:8::2/128); # kcmp@adbc
        -@def $ADMIN_IPS = ($weasel $linus);
        +@def $anarcat = ();
        +@def $anarcat = ($anarcat 203.0.113.1/32); # home IP
        +@def $anarcat = ($anarcat 2001:DB8::DEAD/128 2001:DB8:F00F::/56); # home IPv6
        +@def $ADMIN_IPS = ($weasel $linus $anarcat);


         @def $BASE_SSH_ALLOWED = ();

 4. Then you can commit this and *push*:

        git commit -m'add my home address to the allow list' && git push

 5. Then you should login to one of the hosts and make sure the code
    applies correctly:

        ssh -tt perdulce.torproject.org sudo puppet agent -t

Puppet shows colorful messages. If nothing is red and it returns
correctly, you are done. If that doesn't work, go back to step 2. If
that doesn't work, ask for help from your colleague in the Tor
sysadmin team.

If this works, congratulations, you have made your first change across
the entire Puppet infrastructure! You might want to look at the rest
of the documentation to learn more about how to do different tasks and
how things are setup. A key "How to" we recommend is the `Progressive
deployment` section below, which will teach you how to make a change
like the above while making sure you don't break anything even if it
affects a lot of machines.

# How-to

## Modifying an existing configuration

For new deployments, this is *NOT* the preferred method. For example,
if you are deploying new software that is not already in use in our
infrastructure, do *not* follow this guide and instead follow the
`Adding a new module` guide below.

If you are touching an *existing* configuration, things are much
simpler however: you simply go to the module where the code already
exists and make changes. You `git commit` and `git push` the code,
then immediately run `puppet agent -t` on the affected node.

Look at the `File layout` section above to find the right piece of
code to modify. If you are making changes that potentially affect more
than one host, you should also definitely look at the `Progressive
deployment` section below.

## Adding a new module

This is a broad topic, but let's take the Prometheus monitoring system
as an example which followed the [role/profile/module][]
pattern.

First, the [Prometheus modules on the Puppet forge][] were evaluated
for quality and popularity. There was a clear winner there: the
[Prometheus module][] from [Vox Populi][] had hundreds of thousands
more downloads than the [next option][], which was deprecated.

[next option]: https://forge.puppet.com/brutus777/prometheus
[Vox Populi]: https://voxpupuli.org/
[Prometheus module]: https://forge.puppet.com/puppet/prometheus
[Prometheus modules on the Puppet forge]: https://forge.puppet.com/modules?q=prometheus

Next, the module was added to the Puppetfile (in
`3rdparty/Puppetfile`):

    mod 'puppet-prometheus', '6.4.0'

... and librarian was ran:

    librarian-puppet install

This fetched a lot of code from the Puppet forge: the stdlib, archive
and system modules were all installed or updated. All those modules
were audited manually, by reading each file and looking for obvious
security flaws or back doors. Then the code was committed into git:

    git add 3rdparty
    git commit -m'install prometheus module after audit'

Then the module was configured in a profile, in `modules/profile/manifests/prometheus/server.pp`:

    class profile::prometheus::server {
      class {
        'prometheus::server':
          # follow prom2 defaults
          localstorage        => '/var/lib/prometheus/metrics2',
          storage_retention   => '15d',
      }
    }

The above contains our local configuration for the upstream
`prometheus::server` class installed in the `3rdparty` directory. In
particular, it sets a retention period and a different path for the
metrics, so that they follow the new Prometheus 2.x defaults.

Then this profile was added to a *role*, in
`modules/roles/manifests/monitoring.pp`:

    # the monitoring server
    class roles::monitoring {
      include profile::prometheus::server
    }

Notice how the role does not refer to any implementation detail, like
that the monitoring server uses Prometheus. It looks like a trivial,
useless, class but it can actually grow to include *multiple*
profiles.

Then that role is added to the Hiera configuration of the monitoring
server, in `hiera/nodes/hetzner-nbg1-01.torproject.org.yaml`:

    classes:
      - roles::monitoring

And Puppet was ran on the host, with:

    puppet --enable ; puppet agent -t --noop ; puppet --disable "testing prometheus deployment"

This led to some problems as the upstream module doesn't support
installing from Debian packages. Support for Debian was added to the
code in `3rdparty/modules/prometheus`, and committed into git:

    emacs 3rdparty/modules/prometheus/manifests/*.pp # magic happens
    git commit -m'implement all the missing stuff' 3rdparty
    git push

And the above puppet command-line was ran again, continuing that loop
until things were good.

If you need to deploy the code to multiple hosts, see the `Progressive
deployment` section below. To contribute changes back upstream (and
you should do so), see the section right below.

## Contributing changes back upstream

For simple changes, the above workflow works well, but eventually it
is preferable to actually fork the upstream repository and operate on our
fork until the changes are merged upstream.

First, the modified module is moved out of the way:

    mv 3rdparty/modules/prometheus{,.orig}

The module is then forked on GitHub or wherever it is hosted, and then
added to the Puppetfile:

    mod 'puppet-prometheus',
        :git => 'https://github.com/anarcat/puppet-prometheus.git',
        :branch => 'deploy'

Then Librarian is ran again to fetch that code:

    librarian-puppet install

Because Librarian is a little dumb, it might checkout your module in
"detached head" mode, in which case you will want to fix the checkout:

    cd 3rdparty/modules/prometheus
    git checkout deploy
    git reset --hard origin/deploy
    git pull

Note that the `deploy` branch here is a merge of all the different
branches proposed upstream in different pull requests, but it could
also be the `master` branch or a single branch if only a single pull
request was sent.

Since you now have a clone of the upstream repository, you can push
and pull normally with upstream. When you make a change, however, you
need to commit (and push) the change *both* in the sub-repository and the
main repository:

    cd 3rdparty/modules/prometheus
    $EDITOR manifests/init.pp # more magic stuff
    git commit -m'change the frobatz to a argblu'
    git push
    cd ..
    git commit -m'change the frobatz to a argblu'
    git push

Often, I make commits directly in our main Puppet repository, without
pushing to the third party fork, until I am happy with the code, and
then I craft a nice pretty commit that can be pushed upstream,
reversing that process:

    $EDITOR 3rdparty/prometheus/manifests/init.pp # dirty magic stuff
    git commit -m'change the frobatz to a quuxblah'
    git push
    # see if that works, generally not
    git commit -m'rah. wanted a quuxblutz'
    git push
    # now we are good, update our pull request
    cd 3rdparty/modules/prometheus
    git commit -m'change the frobatz to a quuxblutz'
    git push

It's annoying to double-commit things, but I haven't found a best way
to do so just yet. This problem is further discussed in [ticket #29387][].

Also note that when you update code like this, the `Puppetfile` does
not change, but the `Puppetfile.lock` file *does* change. The `GIT.sha`
parameter needs to be updated. This can be done by hand, but since
that is error-prone, you might want to simply run this to update
modules:

    librarian-puppet update

This will *also* update dependencies so make sure you audit those
changes before committing and pushing.

## Running tests

Ideally, Puppet modules have a test suite. This is done with
[rspec-puppet](https://rspec-puppet.com/) and [rspec-puppet-facts](https://github.com/mcanevet/rspec-puppet-facts). This is not very well
documented upstream, but it's apparently part of the [Puppet
Development Kit](https://puppet.com/docs/pdk/1.x/pdk.html) (PDK). Anyways: assuming tests exists, you will
want to run some tests before pushing your code upstream, or at least
upstream might ask you for this before accepting your changes. Here's
how to get setup:

    sudo apt install ruby-rspec-puppet ruby-puppetlabs-spec-helper ruby-bundler
    bundle install --path vendor/bundle

This installs some basic libraries, system-wide (Ruby bundler and the
rspec stuff). Unfortunately, required Ruby code is rarely all present
in Debian and you still need to install extra gems. In this case we
set it up within the `vendor/bundle` directory to isolate them from
the global search path.

Finally, to run the tests, you need to wrap your invocation with
`bundle exec`, like so:

    bundle exec rake test

## Validating Puppet code

You SHOULD run validation checks on commit locally before pushing your
manifests. To install those hooks, you should clone this repository:

    git clone https://github.com/anarcat/puppet-git-hooks

... and deploy it as a pre-commit hook:

    ln -s $PWD/puppet-git-hooks/pre-commit tor-puppet/.git/hooks/pre-commit

A server-side validation hook hasn't been enabled yet because our
manifests would sometimes fail and the hook was found to be somewhat
slow. That is being worked on in [issue 31226][].

## Listing all hosts under puppet

This will list all active hosts known to the Puppet master:

    ssh -t pauli.torproject.org 'sudo -u postgres psql puppetdb -P pager=off -A -t -c "SELECT c.certname FROM certnames c WHERE c.deactivated IS NULL"'

The following will list all hosts under Puppet and their `virtual`
value:

    ssh -t pauli.torproject.org "sudo -u postgres psql puppetdb -P pager=off -F',' -A -t -c \"SELECT c.certname, value_string FROM factsets fs INNER JOIN facts f ON f.factset_id = fs.id INNER JOIN fact_values fv ON fv.id = f.fact_value_id INNER JOIN fact_paths fp ON fp.id = f.fact_path_id INNER JOIN certnames c ON c.certname = fs.certname WHERE fp.name = 'virtual' AND c.deactivated IS NULL\""  | tee hosts.csv

The resulting file is a Comma-Separated Value (CSV) file which can be
used for other purposes later.

Possible values of the `virtual` field can be obtain with a similar
query:

    ssh -t pauli.torproject.org "sudo -u postgres psql puppetdb -P pager=off -A -t -c \"SELECT DISTINCT value_string FROM factsets fs INNER JOIN facts f ON f.factset_id = fs.id INNER JOIN fact_values fv ON fv.id = f.fact_value_id INNER JOIN fact_paths fp ON fp.id = f.fact_path_id WHERE fp.name = 'virtual';\""

The currently known values are: `kvm`, `physical`, and `xenu`.

As a bonus, this query will show the number of hosts running each release:

    SELECT COUNT(c.certname), value_string FROM factsets fs INNER JOIN facts f ON f.factset_id = fs.id INNER JOIN fact_values fv ON fv.id = f.fact_value_id INNER JOIN fact_paths fp ON fp.id = f.fact_path_id INNER JOIN certnames c ON c.certname = fs.certname WHERE fp.name = 'lsbdistcodename' AND c.deactivated IS NULL GROUP BY value_string;

### Other ways of extracting a host list

 * Using the [PuppetDB API][]:

        curl -s -G http://localhost:8080/pdb/query/v4/facts  | jq -r ".[].certname"

   The [fact API][] is quite extensive and allows for very complex
   queries. For example, this shows all hosts with the `apache2` fact
   set to `true`:

        curl -s -G http://localhost:8080/pdb/query/v4/facts --data-urlencode 'query=["and", ["=", "name", "apache2"], ["=", "value", true]]' | jq -r ".[].certname"

   This will list all hosts sorted by their report date, older first,
   followed by the timestamp, space-separated:

        curl -s -G http://localhost:8080/pdb/query/v4/nodes  | jq -r 'sort_by(.report_timestamp) | .[] | "\(.certname) \(.report_timestamp)"' | column -s\  -t

   This will list all hosts with the `roles::static_mirror` class:

        curl -s -G http://localhost:8080/pdb/query/v4 --data-urlencode 'query=inventory[certname] { resources { type = "Class" and title = "Roles::Static_mirror" }} ' | jq .[].certname

   This will show all hosts running Debian buster:

        curl -s -G http://localhost:8080/pdb/query/v4 --data-urlencode 'query=nodes { facts { name = "lsbdistcodename" and value = "buster" }}' | jq .[].certname

 * Using [howto/cumin](howto/cumin)

 * Using LDAP:

        HOSTS=$(ssh alberti.torproject.org 'ldapsearch -h db.torproject.org -x -ZZ -b dc=torproject,dc=org -LLL "hostname=*.torproject.org" hostname | awk "\$1 == \"hostname:\" {print \$2}" | sort')
        for i in `echo $HOSTS`; do mkdir hosts/x-$i 2>/dev/null || continue; echo $i; ssh $i ' ...'; done

    the `mkdir` is so that I can run the same command in many terminal
    windows and each host gets only one once

 [PuppetDB API]: https://puppet.com/docs/puppetdb/4.3/api/index.html
 [fact API]: https://puppet.com/docs/puppetdb/4.3/api/query/v4/facts.html

## Running Puppet everywhere

There are many ways to [run a command on all hosts (see next
section)][], but the TL;DR: is to basically use [cumin](howto/cumin)
and run this command:

[run a command on all hosts (see next section)]: #batch-jobs-on-all-hosts

    cumin -o txt -b 5 '*' 'puppet agent -t'

But before doing this, consider doing a [progressive
deployment](#progressive-deployment) instead.

## Batch jobs on all hosts

With that trick, a job can be ran on all hosts with
[parallel-ssh][], for example, check the `uptime`:

    cut -d, -f1 hosts.hsv | parallel-ssh -i -h /dev/stdin uptime

This would do the same, but only on physical servers:

    grep 'physical$' hosts.hsv | cut -d -f1 | parallel-ssh -i -h /dev/stdin uptime

This would fetch the `/etc/motd` on all machines:

    cut -d -f1 hosts.csv | parallel-slurp -h /dev/stdin -L motd /etc/motd motd

To run batch commands through `sudo` that requires a password, you will need to fool both `sudo` and ssh a little more:

    cut -d -f1 hosts.csv | parallel-ssh -P -I -i -x -tt -h /dev/stdin -o pvs sudo pvs

You should then type your password then Control-d. Warning: this will
show your password on your terminal and probably in the logs as well.

Batch jobs can also be ran on all Puppet hosts with Cumin:

    ssh -N -L8080:localhost:8080 pauli.torproject.org &
    cumin '*' uptime

See [howto/cumin](howto/cumin) for more examples.

 [parallel-ssh]: https://parallel-ssh.org/

## Progressive deployment

If you are making a major change to the infrastructure, you may want
to deploy it progressively. A good way to do so is to include the new
class manually in an existing role, say in
`modules/role/manifests/foo.pp`:

    class role::foo {
      include my_new_class
    }

Then you can check the effect of the class on the host with the
`--noop` mode. Make sure you disable Puppet so that automatic runs do
not actually execute the code, with:

    puppet agent --disable "testing my_new_class deployment"

Then the new manifest can be simulated with this command:

    puppet agent --enable ; puppet agent -t --noop ; puppet agent --disable "testing my_new_class deployment"

Examine the output and, once you are satisfied, you can re-enable the
agent and actually run the manifest with:

    puppet agent --enable ; puppet agent -t

If the change is *inside* an existing class, that change can be
enclosed in a class parameter and that parameter can be passed as an
argument from Hiera. This is how the transition to a managed
`/etc/apt/sources.list` file was done:

 1. first, a parameter was added to the class that would remove the
    file, defaulting to `false`:

        class torproject_org(
          Boolean $manage_sources_list = false,
        ) {
          if $manage_sources_list {
            # the above repositories overlap with most default sources.list
            file {
              '/etc/apt/sources.list':
                ensure => absent,
            }
          }
        }

 2. then that parameter was enabled on one host, say in
    `hiera/nodes/brulloi.torproject.org.yaml`:

        torproject_org::manage_sources_list: true

 3. Puppet was run on that host using the simulation mode:

        puppet agent --enable ; puppet agent -t --noop ; puppet agent --disable "testing my_new_class deployment"

 4. when satisfied, the real operation was done:

        puppet agent --enable ; puppet agent -t --noop

 5. then this was added to two other hosts, and Puppet was ran there

 6. finally, all hosts were checked to see if the file was present on
    hosts and had any content, with [howto/cumin](howto/cumin) (see above for
    alternative way of running a command on all hosts):

        cumin '*' 'du /etc/apt/sources.list'

 7. since it was missing everywhere, the parameter was set to `true`
    by default and the custom configuration removed from the three
    test nodes

 8. then Puppet was ran by hand everywhere, using Cumin, with a batch
    of 5 hosts at a time:

        cumin -o txt -b 5 '*' 'puppet agent -t'

    because Puppet returns a non-zero value when changes are made,
    this will above when any one host in a batch of 5 will actually
    operate a change. You can then examine the output and see if the
    change is legitimate or abort the configuration change.

Once the Puppet agent is disabled on all nodes, it's possible to enable
it and run the agent only on nodes that still have the agent disabled.
This way it's possible to "resume" a deployment when a problem or
change causes the `cumin` run to abort.

    cumin -b 5 '*' 'if test -f /var/lib/puppet/state/agent_disabled.lock; then puppet agent --enable ; puppet agent -t ; fi'

Because the output `cumin` produces groups together nodes that return
identical output, and because `puppet agent -t` outputs unique
strings like catalog serial number and runtime in fractions of a
second, we have made a wrapper called `patc` that will silence those
and will allow cumin to group those commands together:

    cumin -b 5 '*' 'patc'

## Adding/removing a global admin

To add a new sysadmin, you need to add their SSH key to the root
account everywhere. This can be done in the `profile::admins::key`
field in `hiera/common.yaml`.

You also need to add them to the `adm` group in LDAP, see [adding
users to a group in LDAP](howto/ldap#adding-removing-users-in-a-group).

## Troubleshooting

### Running Puppet by hand and logging

When a Puppet manifest is not behaving as it should, the first step is
to run it by hand on the host:

    puppet agent -t

If that doesn't yield enough information, you can see pretty much
everything that Puppet does with the `--debug` flag. This will, for
example, include `Exec` resources `onlyif` commands and allow you to
see why they do not work correctly (a common problem):

    puppet agent -t --debug

Finally, some errors show up only on the Puppet server: you can look in
`/var/log/daemon.log` there for errors that will only show up there.

### Finding exported resources with SQL queries

Connecting to the PuppetDB database itself can sometimes be easier
than trying to operate the API. There you can inspect the entire thing
as a normal SQL database, use this to connect:

    sudo -u postgres psql puppetdb

It's possible exported resources do surprising things sometimes. It is
useful to look at the actual PuppetDB to figure out which tags
exported resources have. For example, this query lists all exported
resources with `troodi` in the name:

    SELECT certname_id,type,title,file,line,tags FROM catalog_resources WHERE exported = 't' AND title LIKE '%troodi%';

Keep in mind that there are [automatic tags](https://puppet.com/docs/puppet/6.4/lang_tags.html) in exported resources
which can complicate things.

### Finding exported resources with PuppetDB

This query will look for exported resources with the `type`
`Backupninja::Server::Account` (which can be a class, define, or
builtin resource) and a `title` (the "name" of the resource as defined
in the manifests) of `backup-blah@backup.koumbit.net`:

    curl -s -X POST http://localhost:8080/pdb/query/v4 \
        -H 'Content-Type:application/json' \
        -d '{"query": "resources { type = \"Backupninja::Server::Account\" and title = \"backup-blah@backup.koumbit.net\" }"}' \
        | jq . | less -SR

TODO: update the above query to match resources actually in use at
TPO. That example is from koumbit.org folks.

## Password management

If you need to set a password in a manifest, there are special
functions to handle this. We do not want to store passwords directly
in Puppet source code, for various reasons: it is hard to erase
because code is stored in git, but also, ultimately, we want to
publish that source code publicly.

We use Trocla for this purpose, which generates
random passwords and stores the hash or, if necessary, the clear-text
in a YAML file.

With Trocla, each password is generated on the fly from a secure
entropy source ([Ruby's SecureRandom module][]) and stored inside a
state file (in `/var/lib/trocla/trocla_data.yml`, configured
`/etc/puppet/troclarc.yaml`) on the Puppet master.

Trocla can return "hashed" versions of the passwords, so that the
plain text password is never visible from the client. The plain text
can still be stored on the Puppet master, or it can be deleted once
it's been transmitted to the user or another password manager. This
makes it possible to have Trocla not keep any secret at all.

[Ruby's SecureRandom module]: https://ruby-doc.org/stdlib-1.9.3/libdoc/securerandom/rdoc/SecureRandom.html
[Trocla]: https://github.com/duritong/trocla

This piece of code will generate a [bcrypt][]-hashed password for the
Grafana admin, for example:

    $grafana_admin_password = trocla('grafana_admin_password', 'bcrypt')

The plain-text for that password will never leave the Puppet master. it
will still be stored on the Puppet master, and you can see the value
with:

    trocla get grafana_admin_password plain

... on the command-line.

[bcrypt]: https://en.wikipedia.org/wiki/Bcrypt

A password can also be set with this command:

    trocla set grafana_guest_password plain

Note that this might *erase* other formats for this password, although
those will get regenerated as needed.

Also note that `trocla get` will fail if the particular password or
format requested does not exist. For example, say you generate a
plain-text password with and then get the `bcrypt` version:

    trocla create test plain
    trocla get test bcrypt

This will return the empty string instead of the hashed
version. Instead, use `trocla create` to generate that password. In
general, it's safe to use `trocla create` as it will reuse existing
password. It's actually how the `trocla()` function behaves in Puppet
as well.

TODO: Trocla can provide passwords to classes transparently, without
having to do function calls inside Puppet manifests. For example, this
code:

    class profile::grafana {
        $password = trocla('profile::grafana::password', 'plain')
        # ...
    }

Could simply be expressed as:

    class profile::grafana(String $password) {
        # ...
    }

But this requires a few changes:
 
 1. Trocla needs to be included in Hiera
 2. We need roles to be more clearly defined in Hiera, and use Hiera
    as an ENC so that we can do per-roles passwords (for example),
    which is not currently possible.

## Getting information from other nodes

A common pattern in Puppet is to deploy resources on a given host with
information from another host. For example, you might want to grant
access to host A from host B. And while you can hardcode host B's IP
address in host A's manifest, it's not good practice: if host B's IP
address changes, you need to change the manifest, and that practice
makes it difficult to introduce host C into the pool...

So we need ways of having a node use information from other nodes in
our Puppet manifests. There are 5 methods in our Puppet source code at
the time of writing:

 * Exported resources
 * PuppetDB lookups
 * Puppet Query Language (PQL)
 * LDAP lookups
 * Hiera lookups

This section walks through how each method works, outlining the
advantage/disadvantage of each.

### Exported resources

Our Puppet configuration supports [exported resources](https://puppet.com/docs/puppet/latest/lang_exported.html), a key
component of complex Puppet deployments. Exported resources allow one
host to define a configuration that will be *exported* to the Puppet
server and then *realized* on another host.

We commonly use this to punch holes in the firewall between nodes. For
example, this manifest in the `roles::puppetmaster` class:

    @@ferm::rule::simple { "roles::puppetmaster-${::fqdn}":
        tag         => 'roles::puppetmaster',
        description => 'Allow Puppetmaster access to LDAP',
        port        => ['ldap', 'ldaps'],
        saddr       => $base::public_addresses,
      }

... exports a firewall rule that will, later, allow the Puppet server
to access the LDAP server (hence the `port => ['ldap', 'ldaps']`
line). This rule doesn't take effect on the host applying the
`roles::puppetmaster` class, but only on the LDAP server, through this
rather exotic syntax:

    Ferm::Rule::Simple <<| tag == 'roles::puppetmaster' |>>

This tells the LDAP server to apply whatever rule was exported with
the `@@` syntax and the specified `tag`. Any Puppet resource can be
exported and realized that way.

Note that there are security implications with collecting exported
resources: it delegates the resource specification of a node to
another. So, in the above scenario, the Puppet master could decide to
open *other* ports on the LDAP server (say, the SSH port), because it
exports the port number and the LDAP server just blindly applies the
directive. A more secure specification would explicitly specify the
sensitive information, like so:

    Ferm::Rule::Simple <<| tag == 'roles::puppetmaster' |>> {
        port => ['ldap'],
    }

But then a compromised server could send a different `saddr` and
there's nothing the LDAP server could do here: it cannot override the
address because it's exactly the information we need from the other
server...

### PuppetDB lookups

A common pattern in Puppet is to extract information from host A and
use it on host B. The above "exported resources" pattern can do this
for files, commands and many more resources, but sometimes we just
want a tiny bit of information to embed in a configuration file. This
could, in theory, be done with an exported [concat](https://forge.puppet.com/puppetlabs/concat) resource, but
this can become prohibitively complicated for something as simple as
an allowed IP address in a configuration file.

For this we use the [puppetdbquery module](https://github.com/dalen/puppet-puppetdbquery), which allows us to do
elegant queries against PuppetDB. For example, this will extract the
IP addresses of all nodes with the `roles::gitlab` class applied:

    $allow_ipv4 = query_nodes('Class[roles::gitlab]', 'networking.ip')
    $allow_ipv6 = query_nodes('Class[roles::gitlab]', 'networking.ip6')

This code, in `profile::kgb_bot`, propagates those variables into a
template through the `allowed_addresses` variable, which gets expanded
like this:

    <% if $allow_addresses { -%>
    <% $allow_addresses.each |String $address| { -%>
        allow <%= $address %>;
    <% } -%>
        deny all;
    <% } -%>

Note that there is a potential security issue with that approach. The
same way that exported resources trust the exporter, we trust that the
node exported the right fact. So it's in theory possible that a
compromised Puppet node exports an evil IP address in the above
example, granting access to an attacker instead of the proper node. If
that is a concern, consider using LDAP or Hiera lookups instead.

Also note that this will eventually fail when the node goes down:
after a while, resources are expired from the PuppetDB server and the
above query will return an empty list. This seems reasonable: we do
want to eventually revoke access to nodes that go away, but it's still
something to keep in mind.

Keep in mind that the `networking.ip` fact, in the above example,
might be incorrect in the case of a host that's behind NAT. In that
case, you should use LDAP or Hiera lookups.

Note that this could also be implemented with a `concat` exported
resource, but much harder because you would need some special case
when no resource is exported (to avoid adding the `deny`) and take
into account that other configurations might also be needed in the
file. It would have the same security and expiry issues anyways.

### Puppet query language

Note that there's also a way to do those queries without a Forge
module, through the [Puppet query language](https://puppet.com/docs/puppetdb/5.2/api/query/tutorial-pql.html) and the
`puppetdb_query` function. The problem with that approach is that the
function is not very well documented and the query syntax is somewhat
obtuse. For example, this is what I came up with to do the equivalent
of the `query_nodes` call, above:

    $allow_ipv4 = puppetdb_query(
      ['from', 'facts',
        ['and',
          ['=', 'name', 'networking.ip'],
          ['in', 'certname',
            ['extract', 'certname',
              ['select_resources',
                ['and',
                  ['=', 'type', 'Class'],
                  ['=', 'title', 'roles::gitlab']]]]]]])

It seems like I did something wrong, because that returned an empty
array. I could not figure out how to debug this, and apparently I
needed more functions (like `map` and `filter`) to get what I wanted
(see [this gist](https://gist.github.com/bastelfreak/b9620fa1892ebcc659c442b115db34f9)). I gave up at that point: the `puppetdbquery`
abstraction is much cleaner and usable.

If you are merely looking for a hostname, however, PQL might be a
little more manageable. For example, this is how the
`roles::onionoo_frontend` class finds its backends to setup the
[IPsec](ipsec) network:

    $query = 'nodes[certname] { resources { type = "Class" and title = "Roles::Onionoo_backend" } }'
    $peer_names = sort(puppetdb_query($query).map |$value| { $value["certname"] })
    $peer_names.each |$peer_name| {
      $network_tag = [$::fqdn, $peer_name].sort().join('::')
      ipsec::network { "ipsec::${network_tag}":
        peer_networks => $base::public_addresses
      }
    }

### LDAP lookups

Our Puppet server is hooked up to the LDAP server and has information
about the hosts defined there. Information about the node running the
manifest is available in the global `$nodeinfo` variable, but there is
also a `$allnodeinfo` parameter with information about every host
known in LDAP.

A simple example of how to use the `$nodeinfo` variable is how the
`base::public_address` and `base::public_address6` parameters -- which
represent the IPv4 and IPv6 public address of a node -- are
initialized in the `base` class:

    class base(
      Stdlib::IP::Address $public_address            = filter_ipv4(getfromhash($nodeinfo, 'ldap', 'ipHostNumber'))[0],
      Optional[Stdlib::IP::Address] $public_address6 = filter_ipv6(getfromhash($nodeinfo, 'ldap', 'ipHostNumber'))[0],
    ) {
      $public_addresses = [ $public_address, $public_address6 ].filter |$addr| { $addr != undef }
    }

This loads the `ipHostNumber` field from the `$nodeinfo` variable, and
uses the `filter_ipv4` or `filter_ipv6` functions to extract the IPv4
or IPv6 addresses respectively.

A good example of the `$allnodeinfo` parameter is how the
`roles::onionoo_frontend` class finds the IP addresses of its
backend. After having loaded the host list from PuppetDB, it then uses
the parameter to extract the IP address:

    $backends = $peer_names.map |$name| {
        [
          $name,
          $allnodeinfo[$name]['ipHostNumber'].filter |$a| { $a =~ Stdlib::IP::Address::V4 }[0]
        ] }.convert_to(Hash)

Such a lookup is considered more secure than going through PuppetDB as
LDAP is a trusted data source. It is also our source of truth for this
data, at the time of writing.

### Hiera lookups

For more security-sensitive data, we should use a trusted data source
to extract information about hosts. We do this through Hiera lookups,
with the [lookup](https://puppet.com/docs/puppet/latest/function.html#lookup) function. A good example is how we populate the
SSH public keys on all hosts, for the admin user. In the
`profile::ssh` class, we do the following:

    $keys = lookup('profile::admins::keys', Data, 'hash')

This will lookup the `profile::admin::keys` field in Hiera, which is a
trusted source because under the control of the Puppet git repo. This
refers to the following data structure in `hiera/common.yaml`:

    profile::admins::keys:
      anarcat:
        type: "ssh-rsa"
        pubkey: "AAAAB3[...]"

The key point with Hiera is that it's a "hierarchical" data structure,
so each host can have its own override. So in theory, the above keys
could be overridden per host. Similarly, the IP address information for
each host could be stored in Hiera instead of LDAP. But in practice,
we do not currently do this and the per-host information is limited.

## Revoking and generating a new certificate for a host

Revocation procedures problems were discussed in [33587][] and [33446][].

[33587]: https://bugs.torproject.org/33587
[33446]: https://gitlab.torproject.org/legacy/trac/-/issues/33446#note_2349434

 1. Clean the certificate on the master

        puppet cert clean host.torproject.org

 2. Clean the certificate on the client:

        find /var/lib/puppet/ssl -name host.torproject.org.pem -delete

 3. Then run the bootstrap script on the client from
    `tsa-misc/installer/puppet-bootstrap-client` and get a new checksum

 4. Run `tpa-puppet-sign-client` on the master and pass the checksum

 5. Run `puppet agent -t` to have puppet running on the client again.

## Pager playbook

### catalog run: PuppetDB warning: did not update since \[...\]

If you see an error like:

    Check last node runs from PuppetDB WARNING - cupani.torproject.org did not update since 2020-05-11T04:38:54.512Z

It can also be eventually accompanied with the puppet server reporting
the same problem:

    Subject: ** PROBLEM Service Alert: pauli/puppet - all catalog runs is WARNING **
    [...]
    Check last node runs from PuppetDB WARNING - cupani.torproject.org did not update since 2020-05-11T04:38:54.512Z

One of the following is happening, in decreasing likeliness:

 1. the node's Puppet manifest has an error of some sort that makes it
    impossible to run the catalog
 2. the node is down and has failed to report since the last time
    specified
 3. the Puppet **server** is down and **all** nodes will fail to
    report in the same way (in which case a lot more warnings will
    show up, and other warnings about the server will come in)

The first situation will usually happen after someone pushed a commit
introducing the error. We try to keep all manifests compiling all the
time and such errors should be immediately fixed. Look at the history
of the Puppet source tree and try to identify the faulty
commit. Reverting such a commit is acceptable to restore the service.

The second situation can happen if a node is in maintenance for an
extended duration. Normally, the node will recover when it goes back
online. If a node is to be permanently retired, it should be removed
from Puppet, using the [host retirement procedures](howto/retire-a-host).

Finally, if the main Puppet **server** is down, it should definitely
be brought back up. See disaster recovery, below.

In any case, running the Puppet agent on the affected node should give
more information:

    ssh NODE puppet agent -t

### Problems pushing to the Puppet server

Normally, when you push new commits to the Puppet server, a hook runs
and updates the working copy. But sometimes this fails with an error
like:

    remote: error: unable to unlink old 'modules/ipsec/misc/config.yaml': Permission denied.

The problem, in such cases, is that the files in the `/etc/puppet/`
checkout are not writable by your user. It could also happen that the
repository itself (in `/srv/puppet.torproject.org/git/tor-puppet`)
could have permission issues.

This problem is described in [issue 29663][] and is due to someone
not pushing properly before you. To fix the permissions, try:

    sudo chown -R root:adm /etc/puppet
    sudo chown :puppet /etc/puppet/secret
    sudo chmod -R g+rw /etc/puppet
    sudo chmod g-w /etc/puppet/secret

[issue 29663]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/29663

A similar recipe could be applied to the git repository, as
needed. Hopefully this will be resolved when we start deploying with a
role account instead.

## Disaster recovery

Ideally, the main Puppet server would be deployable from Puppet
bootstrap code and the [main installer](new-machine). But in practice, much of
its configuration was done manually over the years and it MUST be
restored from [backups](backup) in case of failure.

This probably includes a restore of the [PostgreSQL](postgresql) database
backing the PuppetDB server as well. It's *possible* this step *could*
be skipped in an emergency, because most of the information in
PuppetDB is a cache of exported resources, reports and facts. But it
could also break hosts and make converging the infrastructure
impossible, as there might be dependency loops in exported resources.

In particular, the Puppet server needs access to the LDAP server, and
that is configured in Puppet. So if the Puppet server needs to be
rebuilt from scratch, it will need to be manually allowed access to
the LDAP server to compile its manifest.

So it is strongly encouraged to restore the PuppetDB server database
as well in case of disaster.

This also applies in case of an IP address change of the Puppet
server, in which case access to the LDAP server needs to be manually
granted before the configuration can run and converge. This is a known
bootstrapping issue with the Puppet server and is further discussed in
the [design section](#ldap-integration).

# Reference

This documents generally how things are setup.

## Installation

Setting up a new Puppet server from scratch is not supported, or, to
be more accurate, would be somewhat difficult. The server expects
various external services to populate it with data, in particular:

 * it [fetches data from LDAP](#ldap-integration)
 * [Nagios generates the NRPE configuration](#nagios-integration)
 * the [letsencrypt repository manages the TLS certificates](#lets-encrypt-tls-certificates)

The auto-ca component is also deployed manual, and so are the git
hooks, repositories and permissions.

This needs to be documented, automated and improved. Ideally, it
should be possible to install a new Puppet server from scratch using
nothing but a Puppet bootstrap manifest, see [issue 30770][] and
[issue 29387][], along with [discussion about those improvements in
this page](#proposed-solution), for details.

[issue 30770]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/30770

## SLA

No formal SLA is defined. Puppet runs on a fairly slow `cron` job so
doesn't have to be highly available right now. This could change in
the future if we rely more on it for deployments.

## Design

The Puppet server and PuppetDB currently live on `pauli`. That server
was setup in 2011 by weasel. It follows the configuration of the
Debian Sysadmin (DSA) Puppet server, which has its source code
available in the [dsa-puppet repository](https://salsa.debian.org/dsa-team/mirror/dsa-puppet/). 

The service is maintained by TPA and manages *all* TPA-operated
machines. Ideally, all services are managed by Puppet, but
historically, only basic services were configured through Puppet,
leaving service admins responsible for deploying their services on top
of it. That tendency has shifted recently (~2020) with the deployment
of the [GitLab](gitlab) service through Puppet, for example.

The source code to the Puppet manifests (see below for a Glossary) is
managed through git on a repository hosted directly on the Puppet
server. Agents are deployed as part of the [install process](new-machine), and
talk to the central server using a Puppet-specific certificate
authority (CA).

As mentioned in the [installation section](#installation), the Puppet server
assumes a few components (namely [LDAP](ldap), [Nagios](nagios), [Let's
Encrypt](tls) and auto-ca) feed information into it. This is also
detailed in the sections below. In particular, Puppet acts as a
duplicate "source of truth" for some information about servers. For
example, LDAP has a "purpose" field describing what a server is for,
but Puppet also has the concept of a role, attributed through Hiera
(see [issue 30273][]). A similar problem exists with IP addresses and
user access control, in general.

[issue 30273]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/30273

Puppet is generally considered stable, but the code base is somewhat
showing its age and has accumulated some technical debt.

For example, much of the Puppet code deployed is specific to Tor (and
DSA, to a certain extent) and therefore is only maintained by a
handful of people. It would be preferable to migrate to third-party,
externally maintained modules (e.g. [systemd](https://gitlab.torproject.org/tpo/tpa/team/-/issues/33449), but also many
others, see [issue 29387][] for details). A similar problem exists
with custom Ruby code implemented for various functions, which is
being replaced with Hiera ([issue 30020][]).

The Puppet infrastructure being kept up to date with the latest
versions in Debian but will require some work to port to Puppet 6, as
the current deployment system ("puppetmaster") has been removed in
that new release (see [issue 33588][]).

[issue 33588]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/33588

### Glossary

This is a subset of the [Puppet glossary](https://puppet.com/docs/puppet/latest/glossary.html) to quickly get you
started with the vocabulary used in this document.

 * **Puppet node**: a machine (virtual or physical) running Puppet
 * **Manifest**: Puppet source code
 * **Catalog**: a set of compiled of Puppet source which gets applied
   on a **node** by a **Puppet agent**
 * **Puppet agents**: the Puppet program that runs on all nodes to
   apply manifests
 * **Puppet server**: the server which all **agents** connect to to
   fetch their **catalog**, also known as a **Puppet master** in older
   Puppet versions (pre-6)
 * **Facts**: information collected by Puppet agents on nodes, and
   exported to the Puppet server
 * **Reports**: log of changes done on nodes recorded by the Puppet
   server
 * **[PuppetDB](https://puppet.com/docs/puppetdb/) server**: an application server on top of a PostgreSQL
   database providing an [API](https://puppet.com/docs/puppetdb/5.2/api/index.html) to query various resources like node
   names, facts, reports and so on

### File layout

The Puppet server and PuppetDB server run on
`pauli.torproject.org`. That is where the main git repository
(`tor-puppet`) lives, in
`/srv/puppet.torproject.org/git/tor-puppet`. That repository has hooks
to populate `/etc/puppet` which is the live checkout from which the
Puppet server compiles its catalogs.
  
All paths below are relative to the root of that git repository.

- `3rdparty/modules` include modules that are shared publicly and do
  not contain any TPO-specific configuration. There is a `Puppetfile`
  there that documents where each module comes from and that can be
  maintained with [r10k][] or [librarian][].

  [librarian]: https://librarian-puppet.com/
  [r10k]: https://github.com/puppetlabs/r10k/

- `modules` includes roles, profiles, and classes that make the bulk
  of our configuration.

- each node is assigned a "role" through the ENC, in
  `hiera-enc/nodes/$FQDN.yaml`

  To be more accurate, the ENC assigns top-scope `$role` variable to
  each node, which is in turn used to include a `role::$rolename`
  class on each node. This occurs in the default node definition in
  `manifests/site.pp`.

  Some nodes include a list of classes, inherited from the previous
  Hiera-based setup, but we're in the process of transitioning all
  nodes to single role classes, see [issue 40030][] for progress on
  this work.

[issue 40030]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/40030

- The `torproject_org` module
  (`modules/torproject_org/manifests/init.pp`) performs basic host
  initialisation, like configuring Debian mirrors and APT sources,
  installing a base set of packages, configuring puppet and timezone,
  setting up a bunch of configuration files and running `ud-replicate`.

- There is also the `hoster.yaml` file
  (`modules/torproject_org/misc/hoster.yaml`) which defines hosting
  providers and specifies things like which network blocks they use,
  if they have a DNS resolver or a Debian mirror. `hoster.yaml` is read
  by
  - the `nodeinfo()` function
    (`modules/puppetmaster/lib/puppet/parser/functions/nodeinfo.rb`),
    used for setting up the `$nodeinfo` variable
  - `ferm`'s `def.conf` template (`modules/ferm/templates/defs.conf.erb`)

- The root of definitions and execution is in Puppet is found in
  the `manifests/site.pp` file. Its purpose is to include a role class
  for the node as well as a number of other classes which are common
  for all nodes.

Note that the above is the current state of the file hierarchy. As
part Hiera transition ([issue 30020][]), a lot of the above
architecture will change in favor of the more standard
[role/profile/module][] pattern.

Note that this layout might also change in the future with the
introduction of a role account ([issue 29663][]) and when/if the
repository is made public (which requires changing the layout).

See [ticket #29387][] for an in-depth discussion.

[issue 29387]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/29387
[role/profile/module]: https://puppet.com/docs/pe/2017.2/r_n_p_intro.html
[ticket #29387]: https://bugs.torproject.org/29387
[issue 30020]: https://bugs.torproject.org/30020

### Installed packages facts

The `modules/torproject_org/lib/facter/software.rb` file defines our
custom facts, making it possible to get answer to questions like "Is
this host running `apache2`?" by simply looking at a puppet
variable. 

Those facts are deprecated and we should instead install packages
through Puppet instead of manually installing packages on hosts.

### Style guide

Puppet manifests should generally follow the [Puppet style
guide][]. This can be easily done with [Flycheck][] in Emacs,
[vim-puppet][], or a similar plugin in your favorite text editor.

Many files do not *currently* follow the style guide, as they
*predate* the creation of said guide. Files should *not* be completely
reformatted unless there's a good reason. For example, if a
conditional covering a large part of a file is removed and the file
needs to be re-indented, it's a good opportunity to fix style in the
file. Same if a file is split in two components or for some other
reason completely rewritten.

Otherwise the style already in use in the file should be followed.

[Puppet style guide]: https://puppet.com/docs/puppet/4.8/style_guide.html
[Flycheck]: http://flycheck.org/
[vim-puppet]: https://github.com/rodjek/vim-puppet

### External Node Classifier (ENC)

We use an External Node Classifier (or ENC for short) to classify
nodes in different roles but also assign them environments and other
variables. The way the ENC works is that the Puppet server requests
information from the ENC about a node before compiling its catalog.

The Puppet server pulls three elements about nodes from the ENC:

 * `environment` is the standard way to assign nodes to a Puppet
   environment. The default is `production` which is the only
   environment currently deployed.

 * `parameters` is a hash where each key is made available as a
   top-scope variable in a node's manifests. We use this assign a
   unique "role" to each node. The way this works is, for a given role
   `foo`, a class `role::foo` will be included. That class should only
   consist of a set of profile classes.

 * `classes` is an array of class names which Puppet includes on the
   target node. We are currently transitioning from this method of
   including classes on nodes (previously in Hiera) to the `role`
   parameter and unique role classes.

For a given node named `$fqdn`, these elements are defined in
`tor-puppet.git/hiera-enc/nodes/$fqdn.yaml`. Defaults can also be set
in `tor-puppet.git/hiera-enc/nodes/default.yaml`.

#### Role classes

Each host defined in the ENC declares which unique role it should be
attributed through the `parameter` hash. For example, this is what
configures a GitLab runner:

    parameters:
      - role: gitlab::runner

Roles should be *abstract* and *not* implementation specific. Each
role class includes a set of profiles which *are* implementation
specific. For example, the `monitoring` role includes
`profile::prometheus::server` and `profile::grafana`.

As a temporary exception to this rule, old modules can be included as
we transition from the Hiera mechanism, but eventually those should
be ported to shared modules from the Puppet forge, with our glue built
into a profile on top of the third-party module. The role
`role::gitlab` follows that pattern correctly. See [issue 40030][] for
progress on that work.

### Hiera

[Hiera][] is a "key/value lookup tool for configuration data" which
Puppet uses to look up values for class parameters and node
configuration in General.

We are in the process of transitioning over to this mechanism from our
previous set of custom YAML lookup system. This documents the way we
currently use Hiera.

[Hiera]: https://puppet.com/docs/hiera/

#### Common configuration

Class parameters which are common across several or all roles can be
defined in `hiera/common.yaml` to avoid duplication at the role level.

However, unless this parameter can be expected to change or evolve over
time, it's sometimes preferable to hardcode some parameters directly in
profile classes in order to keep this dataset from growing too much,
which can impact performance of the Puppet server and degrade its
readability. In other words, it's OK to place site-specific data in
profile manifests, as long as it may never or very rarely change.

These parameters can be override by role and node configurations.

#### Role configuration

Class parameters specific to a certain node role are defined in
`hiera/roles/${::role}.yaml`. This is the principal method by which we
configure the various profiles, thus shaping each of the roles we
maintain.

These parameters can be override by node-specific configurations.

#### Node configuration

On top of the role configuration, some node-specific configuration can
be performed from Hiera. This should be avoided as much as possible,
but sometimes there is just no other way. A good example was the
`build-arm-*` nodes which included the following configuration:

    bacula::client::ensure: "absent"

This disables backups on those machines, which are normally configured
everywhere. This is done because they are behind a firewall and
therefore not reachable, an unusual condition in the network. Another
example is `nutans` which sits behind a NAT so it doesn't know its own
IP address. To export proper firewall rules, the allow address has
been overridden as such:

    bind::secondary::allow_address: 89.45.235.22

Those types of parameters are normally automatically guess inside
modules' classes, but they are overriddable from Hiera.

Note: eventually *all* host configuration will be done here, but there
are currently still some configurations hardcoded in individual
modules. For example, the Bacula director is hardcoded in the `bacula`
base class (in `modules/bacula/manifests/init.pp`). That should be
moved into a class parameter, probably in `common.yaml`.

### Cron and scheduling

The Puppet agent is *not* running as a daemon, it's running through
good old `cron`.

Puppet runs on each node every four hour, although with a random 2h
jitter, so the actual frequency is somewhere between 4 and 6
hours.

This configuration is in `/etc/cron.d/puppet-crontab` and deployed by
Puppet itself, currently as part of the `torproject_org` module.

### LDAP integration

The Puppet is configured to talk with Puppet through a few custom
functions defined in
`modules/puppetmaster/lib/puppet/parser/functions`. The main plumbing
function is called `ldapinfo()` and connects to the LDAP server
through `db.torproject.org` over TLS on port 636. It takes a hostname
as an argument and will load all hosts matching that pattern under the
`ou=hosts,dc=torproject,dc=org` subtree. If the specified hostname is
the `*` wildcard, the result will be a hash of `host => hash` entries,
otherwise only the `hash` describing the provided host will be
returned.

The `nodeinfo()` function uses that function to populate the global
`$nodeinfo` hash available globally, or, more specifically, the
`$nodeinfo['ldap']` component. It also loads the `$nodeinfo['hoster']`
value from the `whohosts()` function. That function, in turn, tries to
match the IP address of the host against the "hosters" defined in the
`hoster.yaml` file.

The `allnodeinfo()` function does a similar task as `nodeinfo()`,
except that it loads *all* nodes from LDAP, into a single hash. It
does *not* include the "hoster" and is therefore equivalent to calling
`nodeinfo()` on each host and extracting only the `ldap` member hash
(although it is not implemented that way).

Puppet does not require any special credentials to access the LDAP
server. It accesses the LDAP database anonymously, although there is a
firewall rule (defined in Puppet) that grants it access to the LDAP
server. 

There is a bootstrapping problem there: if one would be to rebuild the
Puppet server, it would actually fail to compile its catalog because
it would not be able to connect to the LDAP server to fetch its
catalog, unless the LDAP server has been manually configured to let
the Puppet server through.

NOTE: much (if not all?) of this is being moved into Hiera, in
particular the YAML files. See [issue 30020](https://trac.torproject.org/projects/tor/ticket/30020) for details. Moving
the host information into Hiera would resolve the bootstrapping
issues, but would require, in turn some more work to resolve questions
like how users get granted access to individual hosts, which is
currently managed by `ud-ldap`. We cannot, therefore, simply move host
information from LDAP into Hiera without creating a duplicate source
of truth without rebuilding or tweaking the user distribution
system. See also the [LDAP design document](ldap#Design) for more information
about how LDAP works.

### Nagios integration

Nagios (which is really Icinga, but let's call it Nagios because
that's how it's called everywhere in the source) is hooked into Puppet
through an external sync system. Our [Nagios deployment](nagios) operates
through Git hooks which run a special `Makefile` that compiles and
deploys the Icinga configuration, but also compiles the client-side
NRPE configuration.

The NRPE configuration is generated on the Nagios server and then
pushed to the Puppet server with `rsync` over SSH, using a public key
distributed by Puppet from the `roles::puppetmaster` class. That key
has a restricted `command` field which limits access to the Puppet
manifest, in this single file:

    /etc/puppet/modules/nagios/files/tor-nagios/generated/nrpe_tor.cfg

This file then gets distributed to all nodes through the
`nagios::client` class using a simple `File` resource.

So when a Nagios check is added or changed, Puppet needs to run on all
the affected host for the check to take affect, on top of, of course,
adding the check into the Nagios git repository.

### Let's Encrypt TLS certificates

Public TLS certificates, as issued by Let's Encrypted, are distributed
by Puppet. Those certificates are generated by the "letsencrypt" Git
repository (see the [TLS documentation](tls) for details on that
workflow). The relevant part, as far as Puppet is concerned, is that
certificates magically end up in the following directory when a
certificate is issued or (automatically) renewed:

    /srv/puppet.torproject.org/from-letsencrypt

See also the [TLS deployment docs](tls#lets-encrypt-workflow) for how that directory gets
populated.

Normally, those files would not be available from the Puppet
manifests, but the `ssl` Puppet module uses a special trick whereby
those files are read by Puppet `.erb` templates. For example, this is
how `.crt` files get generated on the Puppet master, in
`modules/ssl/templates/crt.erb`:

    <%=
      fn = "/srv/puppet.torproject.org/from-letsencrypt/#{@name}.crt"
      out = File.read(fn)
      out
    %>

Similar templates exist for the other files.

Those certificates should not be confused with the "auto-ca" TLS
certificates in use internally and which are deployed directly in
`/etc/puppet/modules/ssl/files/`, see below.

### Internal auto-ca TLS certificates

The Puppet server also manages an internal CA which we informally call
"auto-ca". Those certificates are internal in that they are used to
authenticate nodes to each other, not to the public. They are used, for
example, to encrypt connections between mail servers (in Postfix) and
[backup servers](backup) (in Bacula).

The auto-ca deploys those certificates directly inside the Puppet
server checkout, in `/etc/puppet/modules/ssl/files/certs/` and
`.../clientcerts/`. Details of that system are available in the [TLS documentation](tls#internal-auto-ca).

## Issues

There is no issue tracker specifically for this project, [File][] or
[search][] for issues in the [team issue tracker][search] component.

 [File]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/new
 [search]: https://gitlab.torproject.org/tpo/tpa/team/-/issues

## Monitoring and testing

Puppet is hooked into Nagios in two ways:

 * one job runs on the Puppetmaster and checks PuppetDB for
   reports. this was done with a [patched](https://github.com/evgeni/check_puppetdb_nodes/pull/14) version of the
   [check_puppetdb_nodes](https://github.com/evgeni/check_puppetdb_nodes/) Nagios check, now packaged inside the
   `tor-nagios-checks` Debian package
 * another job runs on each Puppet node and will therefore work even
   if the Puppetmaster dies for some reason. this is done with the
   [check_puppet_agent](https://github.com/aswen/nagios-plugins/blob/master/check_puppet_agent) Nagios check, now also packaged inside the
   `tor-nagios-checks` Debian package

This was [implemented in March 2019](https://gitlab.torproject.org/tpo/tpa/team/-/issues/29676). An alternative implementation
[using Prometheus](https://forge.puppet.com/puppet/prometheus_reporter) was considered but [Prometheus still hasn't
replaced Nagios](https://gitlab.torproject.org/tpo/tpa/team/-/issues/29864) at the time of writing.

There are no validation checks and *a priori* no peer review of code:
code is directly pushed to the Puppet server without validation. Work
is being done to [implement automated checks](https://gitlab.torproject.org/tpo/tpa/team/-/issues/31226) but that is only
being deployed on some clients for now.

## Logs and metrics

PuppetDB itself holds performance information about the Puppet agent
runs, which are called "reports". Those reports contain information
about changes operated on each server, how long the agent runs take
and so on. Those metrics could be made more visible by using a
dashboard, but that has not been implemented yet (see [issue
31969][]).

[issue 31969]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/31969

The Puppet server, Puppet agents and PuppetDB keep logs of their
operations. The latter keeps its logs in `/var/log/puppetdb/` for a
maximum of 90 days or 1GB, whichever comes first (configured in
`/etc/puppetdb/request-logging.xml` and
`/etc/puppetdb/logback.xml`). The other logs are sent to `syslog`, and
usually end up in `daemon.log`.

Puppet should hold minimal personally identifiable information, like
user names, user public keys and project names.

## Other documentation

 * [Latest Puppet docs](https://puppet.com/docs/puppet/latest/puppet_index.html) - might be too new, see also the [Puppet
   5.5 docs](https://puppet.com/docs/puppet/5.5/puppet_index.html)
   * [Function reference](https://puppet.com/docs/puppet/latest/function.html)
   * [Type reference](https://puppet.com/docs/puppet/latest/type.html)
 * [Mapping between versions of Puppet Entreprise, Facter, Hiera, Agent, etc](https://puppet.com/docs/pe/2019.0/component_versions_in_recent_pe_releases.html)

# Discussion

This section goes more in depth into how Puppet is setup, why it was
setup the way it was, and how it could be improved.

## Overview

Our Puppet setup dates back from 2011, according to the git history,
and was probably based off the [Debian System Administrator's Puppet
codebase](https://salsa.debian.org/dsa-team/mirror/dsa-puppet) which dates back to 2009.

## Goals

The general goal of Puppet is to provide basic automation across the
architecture, so that software installation and configuration, file
distribution, user and some service management is done from a central
location, managed in a git repository. This approach is often called
[Infrastructure as code](https://en.wikipedia.org/wiki/Infrastructure_as_Code).

This section also documents possible improvements to our Puppet
configuration that we are considering.

### Must have

 * **secure**: only sysadmins should have access to push configuration,
   whatever happens. this includes deploying only audited and verified
   Puppet code into production.
 * **code review**: changes on servers should be verifiable by our peers,
   through a git commit log
 * **fix permissions issues**: deployment system should allow all admins
   to push code to the puppet server without having to constantly fix
   permissions (e.g. trough a [role account](https://gitlab.torproject.org/tpo/tpa/team/-/issues/29663))
 * **secrets handling**: there are some secrets in Puppet. those
   should remain secret.

We mostly have this now, although there are concerns about permissions
being wrong sometimes, which a role account could fix.

### Nice to have

Those are mostly issues with the current architecture we'd like to fix:

 * **Continuous Integration**: before deployment, code should be vetted by
   a peer and, ideally, automatically checked for errors and tested
 * **single source of truth**: when we add/remove nodes, we should not
   have to talk to multiple services (see also the [install automation
   ticket](https://gitlab.torproject.org/tpo/tpa/team/-/issues/31239) and the [new-machine discussion](new-machine#discussion)
 * **collaboration** with other sysadmins outside of TPA, for which we
   would need to...
 * ... **publicize our code** (see [ticket 29387](https://gitlab.torproject.org/tpo/tpa/team/-/issues/29387))
 * **no manual changes**: every change on every server should be committed
   to version control somewhere
 * **bare-metal recovery**: it should be possible to recover a service's
   *configuration* from a bare Debian install with Puppet (and with
   data from the [backup](backup) service of course...)
 * **one commit only**: we shouldn't have to commit "twice" to get
   changes propagated (once in a submodule, once in the parent module,
   for example)

### Non-Goals

 * **ad hoc changes** to the infrastructure. one-off jobs should be
   handled by [fabric](fabric), Cumin, or straight SSH.

## Approvals required

TPA should approve policy changes as per [tpa-rfc-1](/policy/tpa-rfc-1-policy).

## Proposed Solution

To improve on the above "Goals", I would suggest the following
configuration.

TL;DR:

 1. Use a control repository
 2. Get rid of 3rdparty
 3. Deploy with g10k
 4. Authenticate with checksums
 5. Deploy to branch-specific environments
 6. Rename the default branch "production"
 7. Push directly on the Puppet server
 8. Use a role account
 9. Use local test environments
 10. Develop a test suite
 11. Hook into CI
 12. OpenPGP verification and web hook

Steps 1-8 could be implemented without too much difficulty and should
be a mid term objective. Steps 9 to 12 require significantly more work
and could be implemented once the new infrastructure stabilizes.

What follows is an explanation and justification of each step.

### Use a control repository

The base of the infrastructure is a [control-repo](https://puppet.com/docs/pe/latest/control_repo.html) ([example](https://github.com/puppetlabs/control-repo),
[another more complex example](https://github.com/example42/psick))
which chain-loads all the other modules. This implies turning all our
"modules" into "profiles" and moving "real" modules (which are fit for
public consumption) "outside", into public repositories (see also
[issue 29387: publish our puppet repository](https://gitlab.torproject.org/tpo/tpa/team/-/issues/29387)).

Note that the control repository *could* also be public: we could
simply have the private data inside of Hiera or some other private
repository.

The control repository concept is specific to the proprietary version
of Puppet (Puppet Enterprise or PE) but its logic should be usable
with the open source Puppet release as well.

### Get rid of 3rdparty

The control repo's core configuration file is the `Puppetfile`. We
already use a Puppetfile, but only to manage modules inside of the
`3rdparty` directory. Now it would manage *all* modules, or, more
specifically, `3rdparty` would become the default `modules` directory
which would, incidentally, encourage us to upstream our modules and
publish them to the world.

Our current `modules` directory would move into `site-modules`, which
is the designated location for "roles, profiles, and custom
modules". This has been suggested before in [issue 29387: publish our
puppet repository](https://gitlab.torproject.org/tpo/tpa/team/-/issues/29387)) and is important for the `Puppetfile` to do its
job.

### Deploy with g10k

It seems clear that everyone is converging over the use of a
`Puppetfile` to deploy code. While there are still monorepos out
there, but they do make our life harder, especially when we need to
operate on non-custom modules.

Instead, we should converge towards *not* following upstream modules
in our git repository. Modules managed by the `Puppetfile` would *not*
be managed in our git monorepo and, instead, would be deployed by
`r10k` or `g10k` (most likely the latter because of its support for
checksums).

Note that neither `r10k` or `g10k` resolve dependencies in a
`Puppetfile`. We therefore also need a tool to verify the file
correctly lists all required modules. The following solutions need to
be validated but could address that issue:

 * [generate-puppetfile](https://github.com/rnelson0/puppet-generate-puppetfile): take a `Puppetfile` and walk the
   dependency tree, generating a new `Puppetfile` (see also [this
   introduction to the project](https://rnelson0.com/2015/11/06/introducing-generate-puppetfile-or-creating-a-ruby-program-to-update-your-puppetfile-and-fixtures-yml/))
 * [Puppetfile-updater](https://github.com/camptocamp/puppetfile-updater): read the `Puppetfile` and fetch new releases
 * [ra10ke](https://github.com/voxpupuli/ra10ke): a bunch of Rake tasks to validate a `Puppetfile`
   * `r10k:syntax`: syntax check, see also `r10k puppetfile check`
   * `r10k:dependencies`: check for out of date dependencies
   * `r10k:solve_dependencies`: check for **missing** dependencies
   * `r10k:install`: wrapper around `r10k` to install with some
     caveats
   * `r10k:validate`: make sure modules are accessible
   * `r10k:duplicates`: look for duplicate declarations
 * [lp2r10k](https://github.com/dharmabruce/lp2r10k/): convert "librarian" `Puppetfile` (missing
   dependencies) into a "r10k" `Puppetfile` (with dependencies)

Note that this list comes from the [updating your Puppetfile](https://github.com/puppetlabs/r10k/blob/master/doc/updating-your-puppetfile.mkd#automatic-updates)
documentation in the r10k project, which is also relevant here.

### Authenticate code with checksums

This part is the main problem with moving away from a monorepo. By
using a monorepo, we can audit the code we push into production. But
if we offload this to `r10k`, it can download code from wherever the
`Puppetfile` says, effectively shifting our trust path from OpenSSH
to HTTPS, the Puppet Forge, git and whatever remote gets added to the
`Puppetfile`.

There is no obvious solution for this right now, surprisingly. Here
are two possible alternatives:

 1. [g10k](https://github.com/xorpaul/g10k/) supports using a `:sha256sum` parameter to checksum
    modules, but that only works for Forge modules. Maybe we could
    pair this with using an explicit `sha1` reference for git
    repository, ensuring those are checksummed as well. The downside
    of that approach is that it leaves checked out git repositories in
    a "detached head" state.

 2. `r10k` has a [pending pull request](https://github.com/puppetlabs/r10k/pull/823) to add a `filter_command`
    directive which could run after a git checkout has been
    performed. it could presumably be used to verify OpenPGP
    signatures on git commits, although this would work only on
    modules we sign commits on (and therefore not third party)

It seems the best approach would be to use g10k for now with checksums
on both git commit and forge modules.

A validation hook running *before* g10k COULD validate that all `mod`
lines have a `checksum` of some sort...

Note that this approach does *NOT* solve the "double-commit" problem
identified in the Goals. It is believed that only a "monorepo" would
fix that problem and that approach comes in direct conflict with the
"collaboration" requirement. We chose the latter.

This could be implemented as a patch to `ra10ke`.

### Deploy to branch-specific environments

A key feature of r10k (and, of course, g10k) is that they are capable
of deploying code to new environments depending on the branch we're
working on. We would enable that feature to allow testing some large
changes to critical code paths without affecting all servers.

### Rename the default branch "production"

In accordance with Puppet's best practices, the control repository's
default branch would be called "production" and not "master".

Also: Black Lives Matter.

### Push directly on the Puppet server

Because we are worried about the GitLab attack surface, we could still
keep on pushing to the Puppet server for now. The control repository
could be mirrored to GitLab using a deploy key. All other repositories
would be published on GitLab anyways, and there the attack surface
would not matter because of the checksums in the control repository.

### Use a role account

To avoid permission issues, use a role account (say `git`) to accept
pushes and enforce git hooks.

### Use local test environments

It should eventually be possible to test changes locally before
pushing to production. This would involve radically simplifying the
Puppet server configuration and probably either getting rid of the
LDAP integration or at least making it optional so that changes can be
tested without it.

This would involve "puppetizing" the Puppet server configuration so
that a Puppet server and test agent(s) could be bootstrapped
automatically. Operators would run "smoke tests" (running Puppet by
hand and looking at the result) to make sure their code works before
pushing to production.

### Develop a test suite

The next step is to start working on a test suite for services, at
least for new deployments, so that code can be tested without running
things by hand. Plenty of Puppet modules have such test suite,
generally using [rspec-puppet](https://rspec-puppet.com/) and [rspec-puppet-facts](https://github.com/mcanevet/rspec-puppet-facts), and we
already have a few modules in `3rdparty` that have such tests. The
idea would be to have those tests on a per-role or per-profile basis.

The Foreman people have published [their test infrastructure](https://github.com/theforeman/foreman-infra/tree/master/puppet) which
could be useful as inspiration for our purposes here.

### Hook into continuous integration

Once tests are functional, the last step is to move the control
repository into GitLab directly and start running CI against the
Puppet code base. This would probably not happen until GitLab CI is
deployed, and would require lots of work to get there, but would
eventually be worth it.

The GitLab CI would be indicative: an operator would need to push to a
topic branch there first to confirm tests pass but would still push
directly to the Puppet server for production.

Note that we are working on (client-side) validation hooks for now,
see [issue 31226][].

[issue 31226]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/31226

### OpenPGP verification and web hook

To stop pushing directly to the Puppet server, we could implement
OpenPGP verification on the control repository. If a hook checks that
commits are signed by a trusted party, it does not matter where the
code is hosted.

A good reference for OpenPGP verification is [this guix article](https://guix.gnu.org/blog/2020/securing-updates/)
which covers a few scenarios and establishes a pretty solid
verification workflow. There's also a larger project-wide discussion
in [GitLab](howto/gitlab) [issue 81](https://gitlab.torproject.org/tpo/tpa/gitlab/-/issues/81).

We could use the [webhook](https://github.com/voxpupuli/puppet_webhook) system to have GitLab notify the Puppet
server to pull code.

## Cost

N/A.

## Alternatives considered

Ansible was considered for managing [GitLab](gitlab) for a while, but
this was eventually abandoned in favor of using Puppet and the
"Omnibus" package.

For ad hoc jobs, [fabric](fabric) is being used.

For code management, I have done a more extensive review of possible
alternatives. [This talk](https://www.youtube.com/watch?v=RdIyStATgFE) is a good introduction for git submodule,
librarian and r10k. Based on that talk and [these slide](https://arlimus.github.io/slides/librarian.and.r10k/), I've made
the following observations:

### monorepo

This is our current approach, which is that all code is committed in
one monolithic repository. This effectively makes it impossible to
share code outside of the repository with anyone else because there is
private data inside, but also because it doesn't follow the standard
role/profile/modules separation that makes collaboration possible at
all. To work around that, I designed a workflow where we locally clone
subrepos as needed, but this is clunky as it requires to commit every
change twice: one for the subrepo, one for the parent.

Our giant monorepo also mixes all changes together which can be an pro
*and* a con: on the one hand it's easy to see and audit all changes at
once, but on the other hand, it can be overwhelming and confusing.

But it does allow us to integrate with librarian right now and is a
good stopgap solution. A better solution would need to solve the
"double-commit" problem and still allow us to have smaller
repositories that we can collaborate on outside of our main tree.

### submodules

The talk partially covers how difficult `git submodules` work and how
hard they are to deal with. I say partially because submodules are
even harder to deal with than the examples she gives. She shows how
submodules are hard to add and remove, because the metadata is stored
in stored in multiple locations (`.gitsubmodules`, `.git/config`,
`.git/modules/` and the submodule repository itself).

She also mentions submodules don't know about dependencies and it's
likely you will break your setup if you forget one step. (See [this
post](https://web.archive.org/web/20171101202911/http://somethingsinistral.net/blog/git-submodules-are-probably-not-the-answer/) for more examples.)

In my experience, the biggest annoyance with submodules is the
"double-commit" problem: you need to make commits in the submodule,
then *redo* the commits in the parent repository to chase the head of
that submodule. This does not improve on our current situation, which
is that we need to do those two commits anyways in our giant monorepo.

One advantage with submodules is that they're mostly standard:
everyone knows about them, even if they're not familiar and their
knowledge is reusable outside of Puppet.

### librarian

Librarian is written in ruby. It's built on top of [another library
called librarian](https://github.com/applicationsonline/librarian) that is used by Ruby's [bundler](https://gembundler.com/). At the time
of the talk, was "pretty active" but unfortunately, librarian now
seems to be [abandoned](https://github.com/voxpupuli/librarian-puppet/issues/48) so we might be forced to use r10k in the
future, which has a quite different workflow.

One problem with librarian right now is that `librarian update` clears
any existing git subrepo and re-clones it from scratch. If you have
temporary branches that were not pushed remotely, all of those are
lost forever. That's really bad and annoying! it's by design: it
"takes over your modules directory", as she explains in the talk and
everything comes from the Puppetfile.

Librarian does resolve dependencies recursively and store the decided
versions in a lockfile which allow us to "see" what happens when you
update from a Puppetfile.

But there's no cryptographic chain of trust between the repository
where the Puppetfile is and the modules that are checked out. Unless
the module is checked out from git (which isn't the default), only
version range specifiers constrain which code is checked out, which
gives a huge surface area for arbitrary code injection in the entire
puppet infrastructure (e.g. MITM, forge compromise, hostile upstream
attacks)

### r10k

r10k was written because librarian was too slow for large
deployments. But it covers more than just managing code: it also
manages environments and is designed to run on the Puppet master. It
doesn't have dependency resolution or a `Puppetfile.lock`,
however. See [this ticket](https://github.com/puppetlabs/r10k/issues/38), closed in favor of [that one](https://tickets.puppetlabs.com/browse/RK-3).

r10k is more complex and very opiniated: it requires lots of
configuration including its own YAML file, hooks into the Puppetmaster
and can [take a while to deploy](http://garylarizza.com/blog/2014/02/18/puppet-workflow-part-3/). r10k is still in [active
development](https://github.com/puppetlabs/r10k/releases) and is supported by Puppetlabs, so there's [official
documentation](https://puppet.com/docs/pe/2019.1/r10k.html) in the Puppet documentation.

Often used in conjunction with librarian for dependency resolution.

One cool feature is that r10k allows you to create dynamic
environments based on branch names. All you need is a single repo with
a Puppetfile and r10k handles the rest. The problem, of course, is
that you need to trust it's going to do the right thing. There's the
security issue, but there's also the problem of resolving dependencies
and you *do* end up double-committing in the end if you use branches
in sub-repositories. But maybe that is unavoidable.

(Note that there are ways of resolving dependencies with external
tools, like [generate-puppetfile](https://github.com/rnelson0/puppet-generate-puppetfile) ([introduction](https://rnelson0.com/2015/11/06/introducing-generate-puppetfile-or-creating-a-ruby-program-to-update-your-puppetfile-and-fixtures-yml/)) or [this hack
that reformats librarian output](https://github.com/dharmabruce/lp2r10k/blob/master/lp2r10k) or [those rake tasks](https://github.com/voxpupuli/ra10ke). there's
also a [go rewrite called g10k](https://github.com/xorpaul/g10k) that is much faster, but with
similar limitations.)

### git subtree

[This article](https://web.archive.org/web/20171107082413/http://somethingsinistral.net/blog/scaling-puppet-environment-deployment/) mentions git subtrees from the point of view of
Puppet management quickly. It outline how it's cool that the history
of the subtree gets merged as is in the parent repo, which gives us
the best of both world (individual, per-module history view along with
a global view in the parent repo). It makes, however, rebasing in
subtrees impossible, as it breaks the parent merge. You do end up with
some of the disadvantages of the monorepo in the all the code is
actually committed in the parent repo and you *do* have to commit
twice as well.

### subrepo

The [git-subrepo](https://github.com/ingydotnet/git-subrepo) is "an improvement from `git-submodule` and
`git-subtree`". It is a mix between a monorepo and a submodule system,
with modules being stored in a `.gitrepo` file. It is somewhat less
well known than the other alternatives, presumably because it's newer?

It is entirely written in `bash`, which I find somewhat scary. It is
[not packaged in Debian yet](http://bugs.debian.org/911397) but might be soon.

It works around the "double-commit issue" by having a special `git
subrepo commit` command that "does the right thing". That, in general,
is its major flaw: it reproduces many git commands like `init`,
`push`, `pull` as subcommands, so you need to remember which command
to run. To quote the (rather terse) manual:

> All the subrepo commands use names of actual Git commands and try to
> do operations that are similar to their Git counterparts. They also
> attempt to give similar output in an attempt to make the subrepo
> usage intuitive to experienced Git users.
>
> Please note that the commands are not exact equivalents, and do not
> take all the same arguments

Still, its feature set is impressive and could be the perfect mix
between the "submodules" and "subtree" approach of still keeping a
monorepo while avoiding the double-commit issue.

### myrepos

[myrepos](https://myrepos.branchable.com/) is one of many solutions to manage multiple git
repositories. It has been used in the past at my old workplace
(Koumbit.org) to manage and checkout multiple git repositories.

Like Puppetfile without locks, it doesn't enforce cryptographic
integrity between the master repositories and the subrepositories: all
it does is define remotes and their locations.

Like r10k it doesn't handle dependencies and will require extra setup,
although it's much lighter than r10k.

Its main disadvantage is that it isn't well known and might seem
esoteric to people. It also has weird failure modes, but could be used
in parallel with a monorepo. For example, it might allow us to setup
specific remotes in subdirectories of the monorepo automatically.

### Summary table

| Approach   | Pros                       | Cons                                     | Summary                           |
|------------|----------------------------|------------------------------------------|-----------------------------------|
| Monorepo   | Simple                     | Double-commit                            | Status quo                        |
| Submodules | Well-known                 | Hard to use, double-commit               | Not great                         |
| Librarian  | Dep resolution client-side | Unmaintained, bad integration with git   | Not sufficient on its own         |
| r10k       | Standard                   | Hard to deploy, opiniated                | To evaluate further               |
| Subtree    | "best of both worlds"      | Still get double-commit, rebase problems | Not sure it's worth it            |
| Subrepo    | subtree + optional         | Unusual, new commands to learn           | To evaluate further               |
| myrepos    | Flexible                   | Esoteric                                 | might be useful with our monorepo |

### Best practices survey

I made a survey of the community (mostly the [shared puppet
modules](https://gitlab.com/shared-puppet-modules-group/) and [Voxpupuli](https://voxpupuli.org/) groups) to find out what the best
current practices are.

Koumbit uses foreman/puppet but pinned at version 10.1 because it is
the last one supporting "passenger" (the puppetmaster deployment
method currently available in Debian, deprecated and dropped from
puppet 6). They [patched it](https://redmine.koumbit.net/projects/theforeman-puppet/repository/revisions/5b1b0b42f2d7d7b01eacde6584d3) to support `puppetlabs/apache < 6`.
They push to a bare repo on the puppet master, then they have
validation hooks (the inspiration for our own hook implementation, see
[issue 31226][]), and a hook deploys the code to the right branch.

They were using r10k but stopped because they had issues when r10k
would fail to deploy code atomically, leaving the puppetmaster (and
all nodes!) in an unusable state. This would happen when their git
servers were down without a locally cached copy. They also implemented
branch cleanup on deletion (although that could have been done some
other way). That issue was apparently reported against r10k but never
got a response. They now use puppet-librarian in their custom
hook. Note that it's possible r10k does not actually have that issue
because they found the issue they filed and it was... [against
librarian](https://github.com/voxpupuli/librarian-puppet/issues/73)!

Some people in #voxpupuli seem to use the Puppetlabs Debian packages
and therefore puppetserver, r10k and puppetboards. Their [Monolithic
master](https://voxpupuli.org/docs/monolithic/) architecture uses an external git repository, which pings
the puppetmaster through a [webhook](https://github.com/voxpupuli/puppet_webhook) which deploys a
[control-repo](https://puppet.com/docs/pe/latest/control_repo.html) ([example](https://github.com/puppetlabs/control-repo)) and calls r10k to deploy the
code. They also use [foreman](https://www.theforeman.org/) as a node classifier. that procedure
uses the following modules:

 * [puppet/puppetserver](https://forge.puppet.com/puppet/puppetserver)
 * [puppetlabs/puppet_agent](https://forge.puppet.com/puppetlabs/puppet_agent)
 * [puppetlabs/puppetdb](https://forge.puppet.com/puppetlabs/puppetdb)
 * [puppetlabs/puppet_metrics_dashboard](https://forge.puppet.com/puppetlabs/puppet_metrics_dashboard)
 * [voxpupuli/puppet_webhook](https://github.com/voxpupuli/puppet_webhook)
 * [r10k](https://github.com/puppetlabs/r10k) or [g10k](https://github.com/xorpaul/g10k)
 * [Foreman](https://www.theforeman.org/)

They also have a [master of masters](https://voxpupuli.org/docs/master_agent/) architecture for scaling to
larger setups. For scaling, I have found [this article](https://puppet.com/blog/scaling-open-source-puppet/) to be more
interesting, that said.

So, in short, it seems people are converging towards r10k with a
web hook. To validate git repositories, they mirror the repositories
to a private git host.

After writing this document, anarcat decided to try a setup with a
"control-repo" and `g10k`, because the latter can cryptographically
verify third-party repositories, either through a git hash or tarball
checksum. There's still only a single environment (I haven't
implemented the "create an environment on a new branch" hook). And it
often means two checkins when we work on shared modules, but that can
be alleviated by skipping the cryptographic check and trusting
transport by having the Puppetfile chase a branch name instead of a
checksum, during development. In production, of course, a checksum can
then be pinned again, but that is the biggest flaw in that workflow.

### Other alternatives

 * [josh](https://github.com/josh-project/josh): "Combine the advantages of a monorepo with those of
   multirepo setups by leveraging a blazingly-fast, incremental, and
   reversible implementation of git history filtering."
 * [lerna](https://lerna.js.org/): Node/JS multi-project management
 * [lite](https://github.com/splitsh/lite): git repo splitter
 * [git-subsplit](https://github.com/dflydev/git-subsplit): "Automate
   and simplify the process of managing one-way read-only subtree
   splits"
