Add retries for sql database

The aim is to retry db transactions that had failed because of
race-conditions. The fix does adds a guard against unseen
race conditions for some of the functions in the database API.

Change-Id: I251b279ceffd1f3207ee022edb808b5df1520c69

glare/db/sqlalchemy/api.py

@@ -22,6 +22,7 @@ from oslo_db.sqlalchemy import session
 from oslo_log import log as os_logging
 from oslo_utils import timeutils
 import osprofiler.sqlalchemy
+from retrying import retry
 import six
 import sqlalchemy
 from sqlalchemy import and_
@@ -102,6 +103,8 @@ def update(context, artifact_id, values, session):
     return _create_or_update(context, artifact_id, values, session)
 
 
+@retry(retry_on_exception=_retry_on_deadlock, wait_fixed=500,
+       stop_max_attempt_number=50)
 def delete(context, artifact_id, session):
     artifact = _get(context, artifact_id, session)
     artifact.properties = []
@@ -120,6 +123,8 @@ def _drop_protected_attrs(model_class, values):
             del values[attr]
 
 
+@retry(retry_on_exception=_retry_on_deadlock, wait_fixed=500,
+       stop_max_attempt_number=50)
 def _create_or_update(context, artifact_id, values, session):
     with session.begin():
         _drop_protected_attrs(models.Artifact, values)
@@ -524,6 +529,8 @@ def _do_blobs(artifact, new_blobs):
     return blobs_to_update
 
 
+@retry(retry_on_exception=_retry_on_deadlock, wait_fixed=500,
+       stop_max_attempt_number=50)
 def create_lock(context, lock_key, session):
     try:
         session.query(models.ArtifactLock).filter_by(id=lock_key).one()
@@ -538,6 +545,8 @@ def create_lock(context, lock_key, session):
     raise exception.Conflict(msg)
 
 
+@retry(retry_on_exception=_retry_on_deadlock, wait_fixed=500,
+       stop_max_attempt_number=50)
 def delete_lock(context, lock_id, session):
     try:
         session.query(models.ArtifactLock).filter_by(id=lock_id).delete()