fix: [mongo] make charm compatible with mongo versions >= ``4.2``

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

mongo/hooks/mongo_database-relation-joined

@@ -10,8 +10,55 @@ DBNAME=$(relation-get dbname) || {
 }
 
 
+## From: https://stackoverflow.com/questions/16989598
+function version_gt() { test "$(printf '%s\n' "$@" | sort -V | head -n 1)" != "$1"; }
+
+
 ensure_db_docker_running
 
+
+## ReplicaSet initialization
+
+cmd="rs.initiate({ _id: 'rs01', members: [ { _id: 0, host: '$TARGET_SERVICE_NAME:27017' } ]})"
+debug "${WHITE}running:$NORMAL $cmd"
+
+out=$(ddb < <(echo "use $DBNAME";
+              echo "$cmd"))
+
+if [[ "$out" == *"\"codeName\" : \"AlreadyInitialized\""* ]]; then
+    info "ReplicaSet already initialized."
+elif [[ "$out" == *"\"ok\" : 1"* ]]; then
+    info "ReplicaSet initialized. "
+else
+    err "ReplicaSet initialisation failed:"
+    echo "$out" >&2
+    exit 13
+fi
+
+
+## Enable read if db version >= 4.2
+
+if ! version=$(mongo:db:version); then
+    err "Couldn't get database version"
+    exit 1
+fi
+
+echo "Current mongo database version: '$version'." >&2
+
+if version_gt "$version" 4.1; then
+    cmd="db.getMongo().setSecondaryOk()"
+    debug "${WHITE}running:$NORMAL $cmd"
+
+    out=$(ddb < <(echo "use $DBNAME";
+                  echo "$cmd")) || {
+        err "Failed database command. Output:"
+        echo "$out" | prefix "  | " >&2
+        exit 1
+    }
+
+fi
+
+
 if dbs=$(mongo:db:ls); then
     if matching_db=$(e "$dbs" | egrep "[a-zA-Z0-9.-_]*_${DBNAME}"); then
         if e "$dbs" | grep "^${DBNAME}$"; then
@@ -41,23 +88,3 @@ else
     exit 14
 fi
 
-## ReplicaSet initialization
-
-cmd="rs.initiate({ _id: 'rs01', members: [ { _id: 0, host: '$TARGET_SERVICE_NAME:27017' } ]})"
-debug "${WHITE}running:$NORMAL $cmd"
-
-out=$(ddb < <(echo "use $DBNAME";
-              echo "$cmd"))
-
-if [[ "$out" == *"\"codeName\" : \"AlreadyInitialized\""* ]]; then
-    info "ReplicaSet already initialized."
-elif [[ "$out" == *"\"ok\" : 1"* ]]; then
-    info "ReplicaSet initialized. "
-else
-    err "ReplicaSet initialisation failed:"
-    echo "$out" >&2
-    exit 13
-fi
-
-
-

mongo/lib/common

@@ -91,3 +91,15 @@ EOF
     fi
     debug "$out"
 }
+
+
+mongo:db:version() {
+    local out
+    if out=$(ddb < <(echo "db.version()")); then
+        e "$out"
+        return 0
+    else
+        err "Could not query version of database."
+        return 1
+    fi
+}