* 'master' of gitlab.com:gitlab-com/runbooks:
  Update alerts_manual.md
  How to add more slack channels to alertmanager
  Add information about available channels for alertmanager
  Add documentation about snapshot backups from chef
  Add support for killing a Sidekiq Job ID
  Update manage-chef.md
  Update oncall.md
  Update elasticsearch.md
  Update the documentation on runners cache disk space
  add link to on-call log
  Add section of things to do while on-call

* dev/master:
  Update runners_cache_disk_space.md
  Recording rule for gitlab-pages status codes

# Conflicts:
#   alerts/db-under-heavy-load.rules
#   alerts/git-cat-file.rules
#   alerts/postgresql-replication-status.rules

Adjust `FOR` interval on alerts to avoid scrape failure induced alert flapping.

* Monitor ext* and xfs, not NFS filesystem mounts.
* Print filesystem alerts with a percentage, not the raw float.
* Extend SSL cert alerting condition to 30min to avoid lost probes
  triggering alert flapping.

- Changed all alert names to CamelCase (@bjk-gitlab asked for this)
- Improved/fixed some alert conditions and messages
- Try to preserve a tad more labels in expressions (when possible)

Unfortunately the Slack notification templates in Alertmanager rely on
there being only one "title" and "description" value, because they use
the title/description from CommonAnnotations (so those are only present
if they are the same between all alerts resulting from one alerting
rule). So I kept appropriate aggregations and topk-ing in some of the
alerts to not break that assumption.