tree bb033e7558b139933e109cc873fa65ad8ae4d6eb
parent 5e5cb69c5cb55217bb54a5d35dd6d539d86c9c6e
author Dariusz Luksza <dariusz.luksza@gmail.com> 1708101671 +0000
committer Dariusz Luksza <dariusz.luksza@gmail.com> 1708336609 +0000

Add combinedRefsSha1 to metrics

Expose new metric providing a "combined refs SHA-1", which could be
used to ensure eventual consistency of repository refs.

It's based on the `Sha1AllRefs`[1] Groovy script, which will iterate
over all repository refs and combine them into a single SHA-1. Then the
resulting SHA-1 will be truncated to an integer value so that it can
be included in metrics.

Exposing this metric should enable Gerrit admins to detect potential
inconsistencies between nodes. All git repositories are **eventually
consistent** which means that detecting different values for combined
refs SHA-1 is **NOT** equivalent to data inconsistency. But not
reporting a consistent state (when the combined refs SHA-1 across nodes
is the same) for a _reasonable time_ should raise an eyebrow and lead to
an investigation if any of the replication events were lost.

The _reasonable time_ will differ from repository to repository, for
some it may be 2 hours, and for others 24 hours. Meaning, that within
that time the repositories should be consistent at least once. It's on
the Gerrit admin to find the time window that works best for their
repositories.

[1]
https://gerrit.googlesource.com/plugins/scripts/+/refs/heads/master/multi-primary/localrefdb.groovy#142

Bug: Issue 324975825
Change-Id: I2e4dbea0892776069dea371803653b7dd239f7f8