Improve migration script Deployment handling (#412)

Helm could not apply some of the 1.0.0 changes to deployments because
some fields were immutable. So, this adjusts the migration script
to orphan the replicasets and delete the deployments. Then when helm upgrade
recreates the deployments, they will adopt the orphaned replicasets and
gradually recreate both replicasets and pods using the latest spec.

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Stop generating the checksum labels for Auth Secret (#392) when existing secret provided or disabled (by @bmarick)
 * Use `image.pullPolicy` for all containers including init containers that use `image.utilityImage`. (#397) (by @jk464)
 * Add new `image.entrypoint` value to simplify using a custom entry point like `dumb-init` or `pid1` (if installed in the image). (#413) (by @cognifloyd)
+* Improve Deployments migration in `migrations/v1.0/standardize-labels.sh` by temporarily orphaning the old ReplicaSets. (#412) (by @cognifloyd)
 
 ## v1.0.0
 * Bump to latest CircleCI orb versions ([email protected] and [email protected] by @ZoeLeah)

migrations/v1.0/standardize-labels.sh

@@ -7,6 +7,12 @@
 # so that helm upgrade will not create duplicate resources. The new label
 # selectors do not match the old labels, so this script adds the new labels
 # to the old resources. Thus, the new selectors will update them.
+#
+# NOTE: This will orphan all Pods, but they will be adopted by the new Deployments.
+# Specifically, we delete Deployment using propogationPolicy=Orphan,
+# and then when Helm creates the Deployments again, the selector will match the
+# current ReplicaSets (and their Pods) because we added the new labels.
+# Finally, the standard k8s Deployment upgrade will gradually replace old Pods.
 
 # These env vars need to be set to use this script:
 #   RELEASE_NAME (same as .Release.Name)
@@ -19,6 +25,9 @@ RELEASE_NAME=${RELEASE_NAME:-st2}
 NAMESPACE=${NAMESPACE:-default}
 CHART_NAME=${CHART_NAME:-stackstorm-ha} # see Chart.yaml
 
+echo RELEASE_NAME=${RELEASE_NAME}
+echo NAMESPACE=${NAMESPACE}
+echo CHART_NAME=${CHART_NAME}
 
 function klabel_app_instance() {
 	kind=${1}
@@ -40,6 +49,17 @@ function klabel_app_name() {
 		"app.kubernetes.io/name=${app}"
 }
 
+function kdelete_cascade_orphan() {
+	kind=${1}
+	app=${2}
+	kubectl delete "${kind}" \
+		-n "${NAMESPACE}" \
+		-l "vendor=stackstorm" \
+		-l "release=${RELEASE_NAME}" \
+		-l "app=${app}" \
+		--cascade=orphan
+}
+
 function k_get_app_names() {
 	kind=${1}
 	app=${2}
@@ -51,14 +71,17 @@ function k_get_app_names() {
 	| jq -r '.items[] | select(.metadata.name | test("'"${app}"'")).metadata.labels.app'
 }
 
+echo
 echo "Adding label app.kubernetes.io/instance=${RELEASE_NAME} (which will replace release=${RELEASE_NAME}) ..."
+echo
 
 for kind in ConfigMap Secret Ingress Service ServiceAccount Deployment ReplicaSet Pod Job; do
 	klabel_app_instance ${kind}
 done
 
 echo
 echo "Adding label app.kubernetes.io/name=<app> (which will replace app=<app>) ..."
+echo
 
 klabel_app_name ConfigMap st2
 klabel_app_name Secret st2
@@ -83,10 +106,12 @@ deployment_apps=(
 	st2workflowengine
 )
 for app in "${deployment_apps[@]}"; do
-	echo "Deployment app=${app} ..."
-	klabel_app_name Deployment ${app}
+	echo "ReplicaSet and Pods from Deployment app=${app} ..."
 	klabel_app_name ReplicaSet ${app}
 	klabel_app_name Pod ${app}
+	echo "Deleting Deployment app=${app} (orphaning the ReplicaSets)..."
+	kdelete_cascade_orphan Deployment ${app}
+	# do not delete ReplicaSet or the Deployment will not adopt the pods
 done
 
 service_apps=(
@@ -115,3 +140,7 @@ done
 
 klabel_app_name ConfigMap st2tests
 klabel_app_name Pod st2tests
+
+echo
+echo "ReplicaSets from Deployments have been orphaned, but new Deployments will adopt them."
+echo "Make sure to run helm upgrade soon to create the new Deployments."