prom: fix link references, again

## Training course plan

- Where can I find documentation? In the wiki, in [Prometheus](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus) and

  [Grafana](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/howto/grafana)

- Where can I find documentation? In the wiki, in [Prometheus service

  page][] (this page) but also the [Grafana service page][]

- Where do I reach the different web sites for the monitoring service?

  See the [web dashboards section](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#web-dashboards)

  See the [web dashboards section][]

- Where do i watch for alerts? Join the `#tor-alerts` IRC channel! See

  also [how to access alerting history](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#checking-alert-history)

  also [how to access alerting history][]

- How can we use silences to prevent some alerts from firing? See

  [Silencing an alert in advance](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#silencing-an-alert-in-advance) and following

- [Architecture overview](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#design)

- [Alerting philosophy](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#alerting-philosophy)

- [Adding metrics](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#adding-metrics-to-applications)

- [How to add alerts](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#writing-an-alert)

- [Queries cheat sheet](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#queries-cheat-sheet)

- [Alert debugging](https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#alert-debugging):

  [Silencing an alert in advance][] and following

- [Architecture overview][]

- [Alerting philosophy][]

- [Adding metrics][]

- [How to add alerts][]

- [Queries cheat sheet][]

- [Alert debugging][]:

  - Alert unit tests

  - Alert routing tests

  - Ensuring the tags required for routing are there

  - %"TPA-RFC-33-B: Prometheus server merge, more exporters"

  - %"TPA-RFC-33-C: Prometheus high availability, long term metrics, other exporters"

 [Alert debugging]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#alert-debugging

 [Queries cheat sheet]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#queries-cheat-sheet

 [How to add alerts]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#writing-an-alert

 [Adding metrics]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#adding-metrics-to-applications

 [Alerting philosophy]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#alerting-philosophy

 [Architecture overview]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#design

 [Silencing an alert in advance]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#silencing-an-alert-in-advance

 [how to access alerting history]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#checking-alert-history

 [web dashboards section]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus#web-dashboards

 [Grafana service page]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/howto/grafana

 [Prometheus service page]: https://gitlab.torproject.org/tpo/tpa/team/-/wikis/service/prometheus

## Web dashboards

The main Prometheus web interface is available at:

the exporter.

The blackbox exporter is rather peculiar and counter-intuitive, see

the [how to debug the blackbox exporter](#debugging-blackbox-exporter) for

the [how to debug the blackbox exporter][] for

more information.

 [how to debug the blackbox exporter]: #debugging-blackbox-exporter

#### Scrape jobs

In Prometheus's point of view, two information are needed:

to reach. The targets can be `hostname:port` pairs or URLs, depending on the

nature of the type of check being defined.

See [documentation for targets in the

repository](https://gitlab.torproject.org/tpo/tpa/prometheus-alerts/-/blob/main/targets.d/README.md)

for more details

See [documentation for targets in the repository][] for more details

 [documentation for targets in the repository]: https://gitlab.torproject.org/tpo/tpa/prometheus-alerts/-/blob/main/targets.d/README.md

## Writing an alert

alert to fire.

Here is, for example, the first alert in the [`rules.d/tpa_node.rules`

file](https://gitlab.torproject.org/tpo/tpa/prometheus-alerts/-/blob/21d67a21ce9926b2eeef0e14b04bb317fb5c94c0/rules.d/tpa_node.rules):

file][]:

 [`rules.d/tpa_node.rules` file]: https://gitlab.torproject.org/tpo/tpa/prometheus-alerts/-/blob/21d67a21ce9926b2eeef0e14b04bb317fb5c94c0/rules.d/tpa_node.rules

```

  - alert: JobDown

 [Prometheus template reference]: https://prometheus.io/docs/prometheus/latest/configuration/template_reference/

 [Alertmanager template reference]: https://prometheus.io/docs/alerting/latest/notifications/

 [limited set of built-in functions]: https://pkg.go.dev/text/template#hdr-Functions

 [Limited set of built-in functions]: https://pkg.go.dev/text/template#hdr-Functions

 [Golang templates]: https://pkg.go.dev/text/template

### Writing a playbook

[metrics in your application]: #adding-metrics-to-applications

[scraped by Prometheus]: #adding-scrape-targets

[Alerting philosophy]: #alerting-philosophy

[alerting rule]: https://prometheus.io/docs/prometheus/latest/configuration/alerting_rules/

[recording rules documentation]: https://prometheus.io/docs/prometheus/latest/configuration/recording_rules/#recording-rules

[aggregation operators]: https://prometheus.io/docs/prometheus/latest/querying/operators/#aggregation-operators

If you can't access the dashboard at all or if the above seems too

complicated, [Grafana][] can be used as a debugging tool for metrics

as well. In the [Explore](https://grafana.torproject.org/explore) section, you can input Prometheus

as well. In the [Explore][] section, you can input Prometheus

metrics, with auto-completion, and inspect the output directly.

 [Explore]: https://grafana.torproject.org/explore

There's also the [Grafana availability dashboard][], see the [Alerting

dashboards][] section for details.