[Feature flag] Rollout of `:load_balancing_improved_caught_up_hosts_check`
Summary
This issue is to rollout the feature on production,
that is currently behind the <feature-flag-name>
feature flag.
Owners
- Team: Memory
- Most appropriate slack channel to reach out to:
#g_memory
- Best individual to reach out to:
@alipniagov
@nmilojevic1
- PM:
@fzimmer
The Rollout Plan
- Rollout on staging
- Percentage Rollout on GitLab.com
- Rollout Feature for everyone as soon as it's ready
Expectations
What are we expecting to happen?
We should be less often fallback to primary if not all replicas are caught up:
https://log.gprd.gitlab.net/goto/1916610d7d3eba60ba9ee5655a5e4675
What might happen if this goes wrong?
We don't expect that. If to imagine, Load Balancing may be unstable: e.g. too many calls to primary, or calls to the replicas which are not caught up.
What can we monitor to detect problems with this?
- a dedicated new metric on the distribution on finding caught up replica or falling to primary: https://log.gprd.gitlab.net/app/visualize#/edit/8cc227f0-dd87-11eb-bfb9-1fcb9ca7f31a?_g=h@c823129&_a=h@0ddfd15
- Postgres overview: https://dashboards.gitlab.net/d/000000144/postgresql-overview?orgId=1
Rollout Steps
Rollout on non-production environments
-
Ensure that the feature MRs have been deployed to non-production environments. -
/chatops run auto_deploy status <merge-commit-of-your-feature>
-
-
Enable the feature globally on non-production environments. -
/chatops run feature set <feature-flag-name> true --dev
-
/chatops run feature set <feature-flag-name> true --staging
-
-
Verify that the feature works as expected. Posting the QA result in this issue is preferable.
Preparation before production rollout
-
Ensure that the feature MRs have been deployed to both production and canary. -
/chatops run auto_deploy status <merge-commit-of-your-feature>
-
-
Check if the feature flag change needs to be accompanied with a change management issue. Cross link the issue here if it does. -
Ensure that you or a representative in development can be available for at least 2 hours after feature flag updates in production. If a different developer will be covering, or an exception is needed, please inform the oncall SRE by using the @sre-oncall
Slack alias. -
Ensure that documentation has been updated (More info). -
Announce on the feature issue an estimated time this will be enabled on GitLab.com. -
If the feature might impact the user experience, notify #support_gitlab-com
and your team channel (more guidance when this is necessary in the dev docs). - [-] If the feature flag in code has an actor, enable it on GitLab.com for testing groups/projects.
- [-]
/chatops run feature set --<actor-type>=<actor> <feature-flag-name> true
- [-]
-
Verify that the feature works as expected. Posting the QA result in this issue is preferable.
Global rollout on production
-
Incrementally roll out the feature. - If the feature flag in code has an actor, perform actor-based rollout.
- [-]
/chatops run feature set <feature-flag-name> <rollout-percentage> --actors
- [-]
- If the feature flag in code does NOT have an actor, perform time-based rollout (random rollout).
-
/chatops run feature set <feature-flag-name> <rollout-percentage>
-
- Enable the feature globally on production environment.
-
/chatops run feature set <feature-flag-name> true
-
- If the feature flag in code has an actor, perform actor-based rollout.
-
Announce on the feature issue that the feature has been globally enabled. -
Wait for at least one day for the verification term.
Release the feature
After the feature has been deemed stable, the clean up should be done as soon as possible to permanently enable the feature and reduce complexity in the codebase.
-
Create a merge request to remove <feature-flag-name>
feature flag. Ask for review and merge it.-
Remove all references to the feature flag from the codebase. -
Remove the YAML definitions for the feature from the repository. -
Create a changelog entry.
-
-
Ensure that the cleanup MR has been deployed to both production and canary. If the merge request was deployed before the code cutoff, the feature can be officially announced in a release blog post. -
/chatops run auto_deploy status <merge-commit-of-cleanup-mr>
-
-
Close the feature issue to indicate the feature will be released in the current milestone. -
Clean up the feature flag from all environments by running these chatops command in #production
channel:-
/chatops run feature delete <feature-flag-name> --dev
-
/chatops run feature delete <feature-flag-name> --staging
-
/chatops run feature delete <feature-flag-name>
-
-
Close this rollout issue.
Rollback Steps
-
This feature can be disabled by running the following Chatops command:
/chatops run feature set load_balancing_improved_caught_up_hosts_check false
Edited by Aleksei Lipniagov