Document and values.yaml updates for leader election customization

Follow-up for #806

README.md

@@ -216,7 +216,14 @@ By default the controller will look for runners in all namespaces, the watch nam
 
 This feature is configured via the controller `--watch-namespace` flag. When a namespace is provided via this flag the controller will only monitor runners in that namespace.
 
-If you plan on installing all instances of the controller stack into a single namespace you will need to make the names of the resources are unique for each stack. In the case of Helm this can be done via the `fullnameOverride` properties. Alternatively, you can install each controller stack into its own unique namespace (relative to other controller stacks in the cluster), avoiding the need to uniquely prefix resources.
+If you plan on installing all instances of the controller stack into a single namespace you will need to make the names of the resources are unique for each stack. In the case of Helm this can be done by giving each a unique release name, or via the `fullnameOverride` properties.
+
+Alternatively, you can install each controller stack into its own unique namespace (relative to other controller stacks in the cluster), avoiding the need to uniquely prefix resources.
+
+When you go to the route of sharing the namespace while giving each a unique Helm release name, you must also ensure the following values are configured correctly:
+
+- `authSecret.name` needs be unique per stack when each stack is tied to runners in different GitHub organizations and repositories AND you want your GitHub credentials to narrowly scoped.
+- `leaderElectionId` needs to be unique per stack. Otherwise, all the stack tries to race onto the leader election lock and results in only one stack can work concurrently.
 
 ## Usage
 

charts/actions-runner-controller/templates/deployment.yaml

@@ -37,11 +37,11 @@ spec:
         {{- $metricsHost := .Values.metrics.proxy.enabled | ternary "127.0.0.1" "0.0.0.0" }}
         {{- $metricsPort := .Values.metrics.proxy.enabled | ternary "8080" .Values.metrics.port }}
         - "--metrics-addr={{ $metricsHost }}:{{ $metricsPort }}"
-        {{- if .Values.controller.enableLeaderElection }}
+        {{- if .Values.enableLeaderElection }}
         - "--enable-leader-election"
         {{- end }}
-        {{- if .Values.controller.leaderElectionId }}
+        {{- if .Values.leaderElectionId }}
-        - "--leader-election-id={{ .Values.controller.leaderElectionId }}"
+        - "--leader-election-id={{ .Values.leaderElectionId }}"
         {{- end }}
         - "--sync-period={{ .Values.syncPeriod }}"
         - "--docker-image={{ .Values.image.dindSidecarRepositoryAndTag }}"

charts/actions-runner-controller/values.yaml

@@ -8,10 +8,9 @@ replicaCount: 1
 
 syncPeriod: 10m
 
-controller:
 enableLeaderElection: true
 # Specifies the controller id for leader election.
-  # Must be unique if more than one controller installed.
+# Must be unique if more than one controller installed onto the same namespace.
 #leaderElectionId: "actions-runner-controller"
 
 # The controller tries its best not to repeat the duplicate GitHub API call