Merge ~martin-hilton/charm-mongodb:004-reduce-restarts into ~mongodb-charmers/charm-mongodb:master

[Martin Hilton]

Reduce the amount of unnecessary service restarts.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[Stuart Bishop (stub)]

Looks good. I think there is an unnecessary import, per inline comment, which can be removed before landing.

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision 3c1439fe6ce619d6dca082f8aadcdf7d36480a99

diff --git a/hooks/hooks.py b/hooks/hooks.py
index c23198b..25e1d69 100755
--- a/hooks/hooks.py
+++ b/hooks/hooks.py
@@ -46,6 +46,7 @@ from charmhelpers.fetch import (
 from charmhelpers.core.host import (
     service,
     lsb_release,
+    file_hash,
 )
 
 from charmhelpers.core.hookenv import (
@@ -117,7 +118,7 @@ MONGO_DOWN = 8
 MONGO_ROLLBACK = 9
 MONGO_REMOVED = 10
 
-# Ill and quick way to make relatinon-departed and relation-broken communicate
+# Ill and quick way to make relation-departed and relation-broken communicate
 was_i_primary = False
 
 ###############################################################################
@@ -976,35 +977,13 @@ def config_changed():
     status_set('maintenance', 'Configuring unit')
     config_data = config()
     juju_log("config_data: {}".format(config_data), level=DEBUG)
+    mongodb_config_hash = file_hash(default_mongodb_config)
     mongodb_config = open(default_mongodb_config).read()
 
-    # Trigger volume initialization logic for permanent storage
-    volid = volume_get_volume_id()
-    if not volid:
-        # Invalid configuration (whether ephemeral, or permanent)
-        stop_hook()
-        mounts = volume_get_all_mounted()
-        if mounts:
-            juju_log("current mounted volumes: {}".format(mounts))
-        juju_log(
-            "Disabled and stopped mongodb service, "
-            "because of broken volume configuration - check "
-            "'volume-ephemeral-storage' and 'volume-map'")
-        sys.exit(1)
-    if volume_is_permanent(volid):
-        # config_changed_volume_apply will stop the service if it finds
-        # it necessary, ie: new volume setup
-        if config_changed_volume_apply():
-            start_hook()
-        else:
-            stop_hook()
-            mounts = volume_get_all_mounted()
-            if mounts:
-                juju_log("current mounted volumes: {}".format(mounts))
-            juju_log(
-                "Disabled and stopped mongodb service "
-                "(config_changed_volume_apply failure)")
-            sys.exit(1)
+    if config_data.changed('volume-ephemeral-storage') or \
+       config_data.changed('volume-map') or \
+       config_data.changed('volume-dev-regexp'):
+        config_changed_volume()
 
     # current ports
     current_mongodb_port = re.search(r'^#*port\s+=\s+(\w+)',
@@ -1047,9 +1026,10 @@ def config_changed():
     # write mongodb logrotate configuration file
     write_logrotate_config(config_data)
 
-    # restart mongodb
-    status_set('maintenance', 'Restarting mongod')
-    restart_mongod()
+    # restart mongodb if the configuration file has changed.
+    if file_hash(default_mongodb_config) != mongodb_config_hash:
+        status_set('maintenance', 'Restarting mongod')
+        restart_mongod()
 
     # attach to replSet ( if needed )
     if config_data['replicaset_master'] != "auto":
@@ -1421,13 +1401,13 @@ def data_relation_changed():
         juju_log("mountpoint from storage subordinate not ready, let's wait")
         return(True)
 
-    config_changed()
+    config_changed_volume()
 
 
 @hooks.hook('data-relation-departed')
 def data_relation_departed():
     juju_log("data_relation_departed")
-    return(config_changed())
+    return(config_changed_volume())
 
 
 @hooks.hook('configsvr-relation-joined')
@@ -1705,6 +1685,37 @@ def volume_get_volume_id():
     return volid
 
 
+# Re-initialize the mounted data volume, if necessary.
+def config_changed_volume():
+    # Trigger volume initialization logic for permanent storage
+    volid = volume_get_volume_id()
+    if not volid:
+        # Invalid configuration (whether ephemeral, or permanent)
+        stop_hook()
+        mounts = volume_get_all_mounted()
+        if mounts:
+            juju_log("current mounted volumes: {}".format(mounts))
+        juju_log(
+            "Disabled and stopped mongodb service, "
+            "because of broken volume configuration - check "
+            "'volume-ephemeral-storage' and 'volume-map'")
+        sys.exit(1)
+    if volume_is_permanent(volid):
+        # config_changed_volume_apply will stop the service if it finds
+        # it necessary, ie: new volume setup
+        if config_changed_volume_apply():
+            start_hook()
+        else:
+            stop_hook()
+            mounts = volume_get_all_mounted()
+            if mounts:
+                juju_log("current mounted volumes: {}".format(mounts))
+            juju_log(
+                "Disabled and stopped mongodb service "
+                "(config_changed_volume_apply failure)")
+            sys.exit(1)
+
+
 # Initialize and/or mount permanent storage, it straightly calls
 # shell helper
 def volume_init_and_mount(volid):