2022-06-27: No-op update min number of nodes on all node pools

Production Change

Change Summary

Our k8s node pools across our 4 clusters in production are mostly set with min number of nodes set to 1 (except pages-1 and pages-2 set to 0). During CI Decomposition, we want to avoid scaling down nodes when we shutdown production in an effort to speed up the process when we start services back up.

To this end, we have written a script that will set the minimum number of nodes for each node pool equal to the current number of running nodes.

Since this setting is controlled by our Terraform config, to revert we will simply trigger a TF plan/apply.

Change Details

  1. Services Impacted - ServiceKube
  2. Change Technician - @gsgl
  3. Change Reviewer - @pguinoiseau
  4. Time tracking - 30 minutes
  5. Downtime Component - none

Detailed steps for the change

Change Steps - steps to take to execute the change

Estimated Time to Complete (mins) - 45m

  • Set label changein-progress /label ~change::in-progress
  • SSH to gprd console
  • Run the following script from the ansible-migrations repo: maintenance-mode/bin/update-nodepools-min-nodes.rb -v
  • Confirm that all the node pools minimum node values were updated correctly.
  • Run the config-mgmt scheduled job that reports on out-of-sync master with current state, and apply the plan.
  • Confirm that all the node pools minimum node values were reverted.
  • Set label changecomplete /label ~change::complete

Rollback

Rollback steps - steps to be taken in the event of a need to rollback this change

Estimated Time to Complete (mins) - 30m

If changes have been made to the minimum node values, then:

  • Run the config-mgmt scheduled job that reports on out-of-sync master with current state, and apply the plan.
  • Confirm that all the node pools minimum node values were reverted.
  • Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

  • Metric: Metric Name
    • Location: Dashboard URL
    • What changes to this metric should prompt a rollback: Describe Changes

Change Reviewer checklist

C4 C3 C2 C1:

  • Check if the following applies:
    • The scheduled day and time of execution of the change is appropriate.
    • The change plan is technically accurate.
    • The change plan includes estimated timing values based on previous testing.
    • The change plan includes a viable rollback plan.
    • The specified metrics/monitoring dashboards provide sufficient visibility for the change.

C2 C1:

  • Check if the following applies:
    • The complexity of the plan is appropriate for the corresponding risk of the change. (i.e. the plan contains clear details).
    • The change plan includes success measures for all steps/milestones during the execution.
    • The change adequately minimizes risk within the environment/service.
    • The performance implications of executing the change are well-understood and documented.
    • The specified metrics/monitoring dashboards provide sufficient visibility for the change.
      • If not, is it possible (or necessary) to make changes to observability platforms for added visibility?
    • The change has a primary and secondary SRE with knowledge of the details available during the change window.
    • The labels blocks deployments and/or blocks feature-flags are applied as necessary

Change Technician checklist

  • Check if all items below are complete:
    • The change plan is technically accurate.
    • This Change Issue is linked to the appropriate Issue and/or Epic
    • Change has been tested in staging and results noted in a comment on this issue.
    • A dry-run has been conducted and results noted in a comment on this issue.
    • For C1 and C2 change issues, the change event is added to the GitLab Production calendar.
    • For C1 and C2 change issues, the SRE on-call has been informed prior to change being rolled out. (In #production channel, mention @sre-oncall and this issue and await their acknowledgement.)
    • Release managers have been informed (If needed! Cases include DB change) prior to change being rolled out. (In #production channel, mention @release-managers and this issue and await their acknowledgment.)
    • There are currently no active incidents that are severity1 or severity2
    • If the change involves doing maintenance on a database host, an appropriate silence targeting the host(s) should be added for the duration of the change.
Edited by Gonzalo Servat