Merge lp:~stub/charms/trusty/postgresql/replication-control into lp:charms/trusty/postgresql

[Stuart Bishop]

Add replication-pause and replication-resume actions

Add some actions the Landscape team need for their deployment process.

The actions allow you to enable or disable replication on a hot standby. While disabled, replication does not happen and no writes are made to the hot standby - it remains as a snapshot until replication is resumed.

The dependent branch is just the charm-helpers sync, which is rather large.

[Cory Johns (johnsca)]

Looks good. Seems to work exactly as expected.

+1

review: Approve

[Marco Ceppi (marcoceppi)]

LGTM +1

review: Approve

=== modified file 'Makefile'
--- Makefile	2015-02-24 16:57:31 +0000
+++ Makefile	2015-06-25 12:08:42 +0000
@@ -57,7 +57,7 @@
 	@flake8 -v \
 	    --exclude hooks/charmhelpers,hooks/_trial_temp \
             --ignore=E402 \
-	    hooks testing tests test.py
+	    hooks actions testing tests test.py
 
 sync:
 	@bzr cat \

=== added directory 'actions'
=== removed directory 'actions'
=== added file 'actions.yaml'
--- actions.yaml	1970-01-01 00:00:00 +0000
+++ actions.yaml	2015-06-25 12:08:42 +0000
@@ -0,0 +1,4 @@
+replication-pause:
+    description: Pause replication replay on a hot standby unit.
+replication-resume:
+    description: Resume replication replay on a hot standby unit.

=== added file 'actions/actions.py'
--- actions/actions.py	1970-01-01 00:00:00 +0000
+++ actions/actions.py	2015-06-25 12:08:42 +0000
@@ -0,0 +1,79 @@
+#!/usr/bin/python
+# Copyright 2015 Canonical Ltd.
+#
+# This file is part of the PostgreSQL Charm for Juju.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3, as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranties of
+# MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
+# PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+import os.path
+import sys
+import traceback
+
+
+hooks_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
+                                         '..', 'hooks'))
+if hooks_dir not in sys.path:
+    sys.path.append(hooks_dir)
+
+from charmhelpers.core import hookenv
+import hooks
+
+
+def replication_pause(params):
+    offset = hooks.postgresql_wal_received_offset()
+    if offset is None:
+        hookenv.action_fail('Not a hot standby')
+        return
+    hookenv.action_set(dict(offset=offset))
+
+    cur = hooks.db_cursor(autocommit=True)
+    cur.execute('SELECT pg_is_xlog_replay_paused()')
+    if cur.fetchone()[0] is True:
+        hookenv.action_fail('Already paused')
+        return
+    cur.execute('SELECT pg_xlog_replay_pause()')
+    hookenv.action_set(dict(result='Paused'))
+
+
+def replication_resume(params):
+    offset = hooks.postgresql_wal_received_offset()
+    if offset is None:
+        hookenv.action_fail('Not a hot standby')
+        return
+    hookenv.action_set(dict(offset=offset))
+
+    cur = hooks.db_cursor(autocommit=True)
+    cur.execute('SELECT pg_is_xlog_replay_paused()')
+    if cur.fetchone()[0] is False:
+        hookenv.action_fail('Already resumed')
+        return
+    cur.execute('SELECT pg_xlog_replay_resume()')
+    hookenv.action_set(dict(result='Resumed'))
+
+
+def main(argv):
+    action = os.path.basename(argv[0])
+    params = hookenv.action_get()
+    try:
+        if action == 'replication-pause':
+            replication_pause(params)
+        elif action == 'replication-resume':
+            replication_resume(params)
+        else:
+            hookenv.action_fail('Action {} not implemented'.format(action))
+    except Exception:
+        hookenv.action_fail('Unhandled exception')
+        hookenv.action_set(dict(traceback=traceback.format_exc()))
+
+
+if __name__ == '__main__':
+    main(sys.argv)

=== added symlink 'actions/replication-pause'
=== target is u'actions.py'
=== added symlink 'actions/replication-resume'
=== target is u'actions.py'
=== modified file 'hooks/hooks.py'
--- hooks/hooks.py	2015-06-25 08:11:29 +0000
+++ hooks/hooks.py	2015-06-25 12:08:42 +0000
@@ -980,8 +980,7 @@
         'locale', 'encoding', 'version', 'cluster_name', 'pgdg']
 
     for name in unchangeable_config:
-        if (name in local_state
-                and local_state[name] != config_data.get(name, None)):
+        if config_data._prev_dict is not None and config_data.changed(name):
             valid = False
             log("Cannot change {!r} setting after install.".format(name))
         local_state[name] = config_data.get(name, None)