Allow routing rules to contain shard information

What does this MR do?

This MR updates the gitlab.yml.erb to allow routing rules to contain shard information.

This change is behind a feature flag and is not released to end-users, but is required for gitlab.com to correctly configure our chef nodes, in particular, the console and deployer nodes.

Test plan

1. Set up kind cluster

kind create cluster --config examples/kind/kind-no-ssl.yaml

2. Update examples/kind/values-no-ssl.yaml. Note that redis is omitted since we only have 1 redis configured. The test plan verifies the chart's checker logic to permit routing rules with 3 valid elements.

diff --git a/examples/kind/values-no-ssl.yaml b/examples/kind/values-no-ssl.yaml
index bf8373aef..f92f91d2b 100644
--- a/examples/kind/values-no-ssl.yaml
+++ b/examples/kind/values-no-ssl.yaml
@@ -1,5 +1,9 @@
 # Disable SSL altogether
 global:
+  appConfig:
+    sidekiq:
+      routingRules:
+        - ["resource_boundary=cpu", "cpu_boundary"]
+        - ['*', 'default', 'default']
   hosts:
     https: false

3. Install gitlab

helm upgrade --install gitlab .  --set global.hosts.domain=192.168.1.74.nip.io -f examples/kind/values-base.yaml  -f examples/kind/values-no-ssl.yaml

4. Verify config/gitlab.yml in the sidekiq pod

kubectl exec $(kubectl get pods | grep sidekiq | awk '{print $1}') cat srv/gitlab/config/gitlab.yml

You should see a chunk of the following to show that both old and new formats are rendered:

 sidekiq:
    log_format: json
    routing_rules:
      - ["resource_boundary=cpu","cpu_boundary"]
      - ["*","default","default"]

Related issues

gitlab-com/gl-infra/scalability#3385 (closed)

Author checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, follow the instructions in the "Reviewer Roulette" section of the Danger Bot MR comment, as per the Distribution experimental MR workflow

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Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated -- the feature is behind a feature flag so the documentation on gitlab rails will be added it is ready to be released for self-hosted users.
• Tests added/updated
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened: gitlab-org/omnibus-gitlab!7512 (merged)
• Equivalent MR/issue for Gitlab Operator project opened (see Operator documentation on impact of Charts changes)
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.