Verified Commit 50ae7ec5 authored by anarcat's avatar anarcat
Browse files

fix instance exclusion system 

It seems like the `htools:iextags:FOO` parameter is a PREFIX. So the
previous system didn't actually work, because (e.g.) no web-fsn:* tag
existed.

I have fixed the actual cluster to use service:* tags.
parent 93768f41

howto/ganeti.md

+15 −8
Original line number Diff line number Diff line
@@ -739,9 +739,9 @@ The way to ensure they get distributed properly by the balancing 
algorithm is to "tag" them. For the web nodes, for example, this was

performed on the master:



    gnt-instance add-tags web-fsn-01.torproject.org web-fsn

    gnt-instance add-tags web-fsn-02.torproject.org web-fsn

    gnt-cluster add-tags htools:iextags:web-fsn

    gnt-cluster add-tags htools:iextags:service

    gnt-instance add-tags web-fsn-01.torproject.org service:web-fsn

    gnt-instance add-tags web-fsn-02.torproject.org service:web-fsn



This tells Ganeti that `web-fsn` is an "exclusion tag" and the

optimizer will not try to schedule instances with those tags on the
@@ -750,14 +750,21 @@ same node. 
To see which tags are present, use:



    # gnt-cluster list-tags

    htools:iextags:web-fsn

    htools:iextags:service



You can also find which nodes are assigned to a tag with:



    # gnt-cluster search-tags web-fsn

    /cluster htools:iextags:web-fsn

    /instances/web-fsn-01.torproject.org web-fsn

    /instances/web-fsn-02.torproject.org web-fsn

    # gnt-cluster search-tags service

    /cluster htools:iextags:service

    /instances/web-fsn-01.torproject.org service:web-fsn

    /instances/web-fsn-02.torproject.org service:web-fsn



IMPORTANT: a previous version of this article mistakenly indicated

that a new cluster-level tag had to be created for each service. That

method did *not* work. The [hbal manpage](http://docs.ganeti.org/ganeti/current/man/hbal.html#exclusion-tags) explicitely mentions that

the cluster-level tag is a *prefix* that can be used to create

*multiple* such tags. This configuration also happens to be simpler

and easier to use...



## Adding and removing addresses on instances