2022-11-16: [GPRD] Deploy Consul cluster in k8s (1/5)

Production Change

Change Summary

We're currently running a Consul server cluster on physical VMs using a very old unsupported version of Consul (1.7.2). This CR is just one of several with the end goal being to deploy a Consul server cluster in k8s using the latest version of Consul (using the official and latest consul-k8s chart), decommission the Consul server cluster running on VMs and upgrade/migrate all Consul clients running in k8s and VMs.

We have carried out this process in staging (see CR). It was largely successful with a few lessons learnt along the way that will hopefully make the production deploy even smoother.

This CR aims to:

  • Deploy a Consul 1.7.2 cluster in k8s
  • Join the clusters up
  • Shutdown the Consul cluster running on VMs
  • Update the start_join parameter to point at the cluster on k8s so VMs can successfully bootstrap to the new cluster
  • Make a similar change to Helm values in the consul release so that Consul agents on k8s can bootstrap successfully

Issue: https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/16268
Epic: &844 (closed)

Change Details

  1. Services Impacted - ServiceConsul
  2. Change Technician - @gsgl
  3. Change Reviewer - @f_santos
  4. Time tracking - 2h
  5. Downtime Component - none

Detailed steps for the change

Change Steps - steps to take to execute the change

Estimated Time to Complete (mins) - 2h

  • Set label changein-progress /label ~change::in-progress
  • Deploy a new Consul Server cluster in k8s with the latest chart (0.49.0) and consul image 1.7.2 - MR: gitlab-com/gl-infra/k8s-workloads/gitlab-helmfiles!1310 (merged)
    • NOTE:
      • ui will be disabled otherwise the chart defines ui_config, which is not valid in 1.7.x (Consul will fail to start)
      • client will be disabled otherwise there'll be ports clash with the existing consul release
      • server.replicas will be set to 5 (we will increase this to 10 temporarily later in another CR)
  • Ensure you can see the consul service monitor getting picked up with 5 targets at https://prometheus-gke.<env>.gitlab.net/service-discovery
  • On one of the Consul members (eg. console), run:
    • consul snapshot save <file> - to take a snapshot before we start
    • consul join consul-gl-internal.<env>.gke.gitlab.net - to join the k8s cluster up to the VMs cluster
  • Update the start_join list on the VMs so they can use the exposed service (consul-gl-internal.<env>.gke.gitlab.net) on the Consul k8s cluster (example MR) - MR: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/2498
  • Update client.join: in helmfile values to consul-gl-internal.<env>.gke.gitlab.net instead of sourcing the value from a Chef roles file - MR: gitlab-com/gl-infra/k8s-workloads/gitlab-helmfiles!1320 (merged)
  • 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) - Estimated Time to Complete in Minutes

  • Rollback any MRs that were merged
  • Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

There should be no impact as we're simply joining two Consul clusters.

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.
    • The change execution window respects the Production Change Lock periods.
    • 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.)
    • For C1 and C2 change issues, the SRE on-call provided approval with the eoc_approved label on the issue.
    • For C1 and C2 change issues, the Infrastructure Manager provided approval with the manager_approved label on the issue.
    • 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