Add documentRevisionLimit value to configure the number of document revisions stored in CouchDB (#98)

* feat: Add documentRevisionLimit value to configure the number of document revisions stored in CouchDB

Signed-off-by: Eamonn Mansour <47121388+eamansour@users.noreply.github.com>

* fix: Add random alphanumeric characters suffix to the couchdb-setup job to avoid an error when upgrading the helm chart with a new revision limit

Signed-off-by: Eamonn Mansour <47121388+eamansour@users.noreply.github.com>

* review: Turn couchdb-setup job into a Helm hook to avoid multiple jobs running at the same time

Signed-off-by: Eamonn Mansour <47121388+eamansour@users.noreply.github.com>

* review: Add CouchDB docs to the documentRevisionLimit value

Signed-off-by: Eamonn Mansour <47121388+eamansour@users.noreply.github.com>

---------

Signed-off-by: Eamonn Mansour <47121388+eamansour@users.noreply.github.com>

Author: eamansour

charts/ecosystem/templates/couchdb-setup-job.yaml

@@ -8,6 +8,10 @@ apiVersion: batch/v1
 kind: Job
 metadata:
   name: "{{ .Release.Name }}-couchdb-setup"
+  annotations:
+    "helm.sh/hook": post-install,post-upgrade
+    "helm.sh/hook-weight": "0"
+    "helm.sh/hook-delete-policy": hook-succeeded
 spec:
   ttlSecondsAfterFinished: 120
   backoffLimit: 1
@@ -35,21 +39,49 @@ spec:
           - --for=condition=Ready
           - --timeout=90s
       containers:
-      - name: create-couchdb-users-database
+      - name: create-couchdb-users-database-and-set-revision-limits
         image: {{ .Values.couchdbImage }}
         imagePullPolicy: {{ .Values.pullPolicy }}
         command:
           - /bin/bash
           - -ec
           - |
             auth_header="Authorization: Basic ${GALASA_RAS_TOKEN}"
-            db_exists_code=$(curl --silent --output /dev/null -w "%{http_code}" --head -H "${auth_header}" http://{{ .Release.Name }}-couchdb:5984/_users)
 
-            if [[ ${db_exists_code} == "404" ]]; then
-              curl --silent --show-error -X PUT -H "${auth_header}" http://{{ .Release.Name }}-couchdb:5984/_users
-            else
-              echo "Users database already exists - OK"
-            fi
+            # Sets the document revision limit for a given CouchDB database
+            # Parameters:
+            # $1 - The name of the database to update
+            function set_revision_limit() {
+              database="$1"
+              new_limit="{{ .Values.couchdb.documentRevisionLimit }}"
+
+              echo "Setting revision limit for database ${database} to ${new_limit}"
+              curl --silent --show-error -X PUT -d "${new_limit}" -H "${auth_header}" http://{{ .Release.Name }}-couchdb:5984/${database}/_revs_limit
+              rc=$?
+              if [[ "${rc}" != "0" ]]; then
+                echo "Failed to set revision limit. rc=${rc}"
+              else
+                echo "Revision limit set - OK"
+              fi
+            }
+
+            # Creates the CouchDB _users database if it does not already exist
+            function create_users_db() {
+              db_exists_code=$(curl --silent --output /dev/null -w "%{http_code}" --head -H "${auth_header}" http://{{ .Release.Name }}-couchdb:5984/_users)
+              if [[ ${db_exists_code} == "404" ]]; then
+                curl --silent --show-error -X PUT -H "${auth_header}" http://{{ .Release.Name }}-couchdb:5984/_users
+              else
+                echo "Users database already exists - OK"
+              fi
+            }
+
+            create_users_db
+
+            set_revision_limit "galasa_artifacts"
+            set_revision_limit "galasa_log"
+            set_revision_limit "galasa_run"
+            set_revision_limit "galasa_tokens"
+            set_revision_limit "galasa_users"
         env:
         - name: GALASA_RAS_TOKEN
           valueFrom:

charts/ecosystem/values.yaml

@@ -487,6 +487,12 @@ enginecontroller:
 # The couchdb component stores run history and records, user records and other
 # persistent storage objects.
 couchdb:
+  # The number of document revisions that will be stored in CouchDB for each database used by the Galasa service.
+  # A low value will reduce disk usage and make compaction faster as there are fewer revisions to compact.
+  # However, a low value can also cause more conflicts when replicating databases.
+  # See https://docs.couchdb.org/en/stable/replication/conflicts.html for details around CouchDB conflicts.
+  documentRevisionLimit: 1
+
   # Best practice is to set memory limits for each pod.
   # This section sets some limits which Dex should be happy working within.
   # Omitting this resources: section will cause no memory or cpi limits to be set.