Commit eef8c990 authored by Marcia Ramos's avatar Marcia Ramos

Merge branch 'update-docs-for-lb-idempotent-workers' into 'master'

Update docs for lb workers with deduplication

See merge request gitlab-org/gitlab!79648
parents f4053e39 9997d5ce
......@@ -185,30 +185,6 @@ end
Duplicate jobs can happen when the TTL is reached, so make sure you lower this only for jobs
that can tolerate some duplication.
## Deduplication with load balancing
> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/6763) in GitLab 14.4.
Jobs that declare either `:sticky` or `:delayed` data consistency
are eligible for database load-balancing.
In both cases, jobs are [scheduled in the future](#scheduling-jobs-in-the-future) with a short delay (1 second).
This minimizes the chance of replication lag after a write.
If you really want to deduplicate jobs eligible for load balancing,
specify `including_scheduled: true` argument when defining deduplication strategy:
```ruby
class DelayedIdempotentWorker
include ApplicationWorker
data_consistency :delayed
deduplicate :until_executing, including_scheduled: true
idempotent!
# ...
end
```
### Preserve the latest WAL location for idempotent jobs
> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/69372) in GitLab 14.3.
......
......@@ -259,10 +259,11 @@ these scenarios, since `:always` should be considered the exception, not the rul
To allow for reads to be served from replicas, we added two additional consistency modes: `:sticky` and `:delayed`.
When you declare either `:sticky` or `:delayed` consistency, workers become eligible for database
load-balancing. In both cases, jobs are enqueued with a short delay.
This minimizes the likelihood of replication lag after a write.
load-balancing.
The difference is in what happens when there is replication lag after the delay: `sticky` workers
In both cases, if the replica is not up-to-date and the time from scheduling the job was less than the minimum delay interval,
the jobs sleep up to the minimum delay interval (0.8 seconds). This gives the replication process time to finish.
The difference is in what happens when there is still replication lag after the delay: `sticky` workers
switch over to the primary right away, whereas `delayed` workers fail fast and are retried once.
If they still encounter replication lag, they also switch to the primary instead.
**If your worker never performs any writes, it is strongly advised to apply one of these consistency settings,
......
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