don't lock on delete

we don't need to lock metric on delete but rather we only need to
check if sack is being processed. either:

1) sack is locked, so there's a chance that metric is being processed.
therefore we skip.
2) sack is unlocked, so there's no chance that a concurrent process
will start processing metric as the indexer already says it's already
deleted and no other process can see it as not-deleted.

Change-Id: I8df135621dfabc3d17733a3577d0ea60b30e83e4

gnocchi/cli.py

@@ -216,10 +216,6 @@ class MetricProcessor(MetricProcessBase):
         finally:
             return self._tasks or self.fallback_tasks
 
-    def _sack_lock(self, sack):
-        lock_name = b'gnocchi-sack-%s-lock' % str(sack).encode('ascii')
-        return self._coord.get_lock(lock_name)
-
     def _run_job(self):
         m_count = 0
         s_count = 0
@@ -227,7 +223,7 @@ class MetricProcessor(MetricProcessBase):
         for s in self._get_tasks():
             # TODO(gordc): support delay release lock so we don't
             # process a sack right after another process
-            lock = self._sack_lock(s)
+            lock = in_store.get_sack_lock(self._coord, s)
             if not lock.acquire(blocking=False):
                 continue
             try:

gnocchi/storage/_carbonara.py

@@ -339,14 +339,16 @@ class CarbonaraBasedStorage(storage.StorageDriver):
 
     def delete_metric(self, metric, sync=False):
         LOG.debug("Deleting metric %s", metric)
-        lock = self._lock(metric.id)
+        lock = self.incoming.get_sack_lock(
+            self.coord, self.incoming.sack_for_metric(metric.id))
         if not lock.acquire(blocking=sync):
             raise storage.LockedMetric(metric)
-        try:
-            self._delete_metric(metric)
-            self.incoming.delete_unprocessed_measures_for_metric_id(metric.id)
-        finally:
-            lock.release()
+        # NOTE(gordc): no need to hold lock because the metric has been already
+        #              marked as "deleted" in the indexer so no measure worker
+        #              is going to process it anymore.
+        lock.release()
+        self._delete_metric(metric)
+        self.incoming.delete_unprocessed_measures_for_metric_id(metric.id)
 
     @staticmethod
     def _delete_metric_measures(metric, timestamp_key,

gnocchi/storage/incoming/_carbonara.py

@@ -71,6 +71,11 @@ class CarbonaraBasedStorage(incoming.StorageDriver):
     def remove_sack_group(num_sacks):
         raise NotImplementedError
 
+    @staticmethod
+    def get_sack_lock(coord, sack):
+        lock_name = b'gnocchi-sack-%s-lock' % str(sack).encode('ascii')
+        return coord.get_lock(lock_name)
+
     def _unserialize_measures(self, measure_id, data):
         nb_measures = len(data) // self._MEASURE_SERIAL_LEN
         try: