[Feature flag] Enable use_primary_and_secondary_stores_for_sessions feature flag
Summary
This issue is to rollout MultiStore with fallback mechanism on production,
that is currently behind the use_primary_and_secondary_stores_for_sessions
feature flag.
Owners
- Team: Memory Team
- Most appropriate slack channel to reach out to:
#g_memory
- Best individual to reach out to: @nmilojevic1
- PM: @changzhengliu
Stakeholders
The Rollout Plan
- Percentage Rollout on GitLab.com
- Rollout Feature for everyone as soon as it's ready
Expectations
What are we expecting to happen?
The users should not be affected. They should stay logged in.
We expect to see that both Redis sessions store and Redis shared state are used.
What might happen if this goes wrong?
Disabling this ff unless use_primary_and_secondary_stores_for_sessions
is enabled, could cause that already logged users to be logged out. Make sure that ff use_primary_and_secondary_stores_for_sessions
is enabled before disabling this FF.
What can we monitor to detect problems with this?
-
Metric: Prometheus multi store counters: TBA, here we can see fallback reads to the SharedState
Note: Pay attention to the prometheus metric:
gitlab_redis_multi_store_method_missing_total
, it should be emptyWe should monitor
gitlab_redis_multi_store_read_fallback_total
, when we stop falling back to read to the SharedState, we are safe to use only Redis::Sessions store, and we could remove and clean MultiStore implementation and this feature flag.
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 use_primary_and_secondary_stores_for_sessions true --dev
-
/chatops run feature set use_primary_and_secondary_stores_for_sessions 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. production#6022 (closed) -
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> use_primary_and_secondary_stores_for_sessions 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 use_primary_and_secondary_stores_for_sessions <rollout-percentage> --actors
-
- If the feature flag in code does NOT have an actor, perform time-based rollout (random rollout).
-
/chatops run feature set use_primary_and_secondary_stores_for_sessions <rollout-percentage>
-
- Enable the feature globally on production environment.
-
/chatops run feature set use_primary_and_secondary_stores_for_sessions 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.
(Optional) Release the feature with the feature flag
If you're still unsure whether the feature is deemed stable but want to release it in the current milestone, you can change the default state of the feature flag to be enabled. To do so, follow these steps:
-
Create a merge request with the following changes. Ask for review and merge it. -
Set the default_enabled
attribute in the feature flag definition totrue
. -
Create a changelog entry.
-
-
Ensure that the default-enabling 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-default-enabling-mr>
-
-
Close the feature issue to indicate the feature will be released in the current milestone. -
Set the next milestone to this rollout issue for scheduling the flag removal. -
(Optional) You can create a separate issue for scheduling the steps below to Release the feature. -
Set the title to "[Feature flag] Cleanup <feature-flag-name>
". -
Execute the /copy_metadata <this-rollout-issue-link>
quick action to copy the labels from this rollout issue. -
Link this rollout issue as a related issue. -
Close this rollout issue.
-
WARNING: This approach has the downside that it makes it difficult for us to clean up the flag. For example, on-premise users could disable the feature on their GitLab instance. But when you remove the flag at some point, they suddenly see the feature as enabled and they can't roll it back to the previous behavior. To avoid this potential breaking change, use this approach only for urgent matters.
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 use_primary_and_secondary_stores_for_sessions --dev
-
/chatops run feature delete use_primary_and_secondary_stores_for_sessions --staging
-
/chatops run feature delete use_primary_and_secondary_stores_for_sessions
-
-
Close this rollout issue.
Rollback Steps
-
This feature can be disabled by running the following Chatops command:
/chatops run feature set use_primary_store_as_default_for_sessions false