Retry when checking ceph pool compression mode.

The compression mode after it's set via config-changed might take a
while to fully propagate to the whole cluster, hence the hook may be
done before the cluster is fully configured with the new compression
mode. This is more noticeable in the gate when there are many jobs
running in parallel.

This patch modes the check to its own method wrapped with a
tenacity.retry decorator to make the test more robust.

Closes openstack-charmers#946

zaza/openstack/charm_tests/ceph/tests.py

@@ -1372,25 +1372,29 @@ def test_configure_compression(self):
         with self.config_change(
                 {'bluestore-compression-mode': 'none'},
                 {'bluestore-compression-mode': 'force'}):
-            # Retrieve pool details from Ceph after changing configuration
-            ceph_pools_detail = zaza_ceph.get_ceph_pool_details(
-                model_name=self.model_name)
-            logging.debug('CONFIG_CHANGE: {}'.format(ceph_pools_detail))
             logging.info('Checking Ceph pool compression_mode after to change')
-            self._assert_pools_properties(
-                app_pools, ceph_pools_detail,
-                {'options': {'compression_mode': 'force'}})
+            self._check_pool_compression_mode(app_pools, 'force')
+
+        logging.info('Checking Ceph pool compression_mode after '
+                     'restoring config to previous value')
+        self._check_pool_compression_mode(app_pools, 'none')
+
+    @tenacity.retry(
+        wait=tenacity.wait_exponential(multiplier=1, min=2, max=10),
+        stop=tenacity.stop_after_attempt(10),
+        reraise=True,
+        retry=tenacity.retry_if_exception_type(AssertionError)
+    )
+    def _check_pool_compression_mode(self, app_pools, mode):
         ceph_pools_detail = zaza_ceph.get_ceph_pool_details(
             model_name=self.model_name)
-        logging.debug('AFTER: {}'.format(ceph_pools_detail))
+        logging.debug('ceph_pools_details: %s', ceph_pools_detail)
         logging.debug(juju_utils.get_relation_from_unit(
             'ceph-mon', self.application_name, None,
             model_name=self.model_name))
-        logging.info('Checking Ceph pool compression_mode after restoring '
-                     'config to previous value')
         self._assert_pools_properties(
             app_pools, ceph_pools_detail,
-            {'options': {'compression_mode': 'none'}})
+            {'options': {'compression_mode': mode}})
 
     def test_invalid_compression_configuration(self):
         """Set invalid configuration and validate charm response."""