2022-11-21: [GPRD] Upgrade Consul agents in k8s to 1.13.3 (3/5)

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:

• Increase server replicas to 10 (to handle DNS traffic while we destroy/create Consul clients)
• Update app config to use a temporary Consul DNS iLB backed by Consul server agents
• Remove consul release
• Enable client in the consul-gl release
• Update app config to use the DNS SVC (ie. local node Consul agent or another if unavailable)
• Reduce server replicas to 5

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

Change Details

1. Services Impacted - ServiceConsul ServiceWeb ServiceWebsockets ServiceSidekiq ServiceGit ServiceAPI
2. Change Technician - @gsgl
3. Change Reviewer - @f_santos
4. Time tracking - 1.5hr
5. Downtime Component - none

Detailed steps for the change

Change Steps - steps to take to execute the change

Estimated Time to Complete (mins) - 90min

• Set label changein-progress /label ~change::in-progress
• Increase server.replicas to 10 - MR: gitlab-com/gl-infra/k8s-workloads/gitlab-helmfiles!1340 (merged)
• Update app DB load balancing config to temporarily use the nameserver consul-dns.gprd.gke.gitlab.net:53 (TCP) for DNS resolution - MR: gitlab-com/gl-infra/k8s-workloads/gitlab-com!2333 (merged)
• Remove consul release - MR: gitlab-com/gl-infra/k8s-workloads/gitlab-helmfiles!1341 (merged)
• Enable client in the consul-gl release - MR: gitlab-com/gl-infra/k8s-workloads/gitlab-helmfiles!1342 (merged)
• Update app DB load balancing config to use the nameserver consul-gl-consul-dns.consul.svc.cluster.local:53 (TCP) for DNS resolution
• Reduce replicas for the server down to 5 manually (one at a time) then file an MR to make it official
• Deploy Consul 1.13.3 on VMs by updating the <env>-base.json role in Chef (this won't actually cycle Consul - only install it) - MR: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/2508
• 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

This is the full list of reverts but it depends at what stage of the rollout a rollback is performed:

• Revert change to the app DB load balancing config (ie. the 4x nameserver settings in https://gitlab.com/gitlab-com/gl-infra/k8s-workloads/gitlab-com/-/blob/master/releases/gitlab/values/gprd.yaml.gotmpl)
• Revert the consul release uninstall (revert MR: xxx)
• Revert the change that enabled clients in the consul-gl release (revert MR: xxx)
• Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

• Metric: Platform Triage - Apdex and Error Ratios

  • Location: https://dashboards.gitlab.net/d/general-triage/general-platform-triage?orgId=1
  • What changes to this metric should prompt a rollback: significant drop in apdex and/or error ratio.

• Metric: Patroni - Apdex and Error Ratios in Platform Triage

  • Location: https://dashboards.gitlab.net/d/patroni-main/patroni-overview?orgId=1
  • What changes to this metric should prompt a rollback: significant drop in apdex and/or error ratio.

• Metric: Sidekiq Overview - Agg Queue Length

  • Location: https://dashboards.gitlab.net/d/sidekiq-main/sidekiq-overview
  • What changes to this metric should prompt a rollback: if queues are growing & not coming down, and restarting sidekiq deployments doesn't help.

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.