Refactor work with TaskLog in sqlalchemy.api

Add _task_log_get_query() private method
It is used to remove from task_log_get() and task_log_get_all() session.
parametr and save performance.

task_log_get() method
Remove session parameter from public method.

task_log_get_all() method
Remove session parameter from public method.

task_log_begin_task()
Remove session parameter from public method.
Remove unused return value.

task_log_end_task()
Remove session parameter from public method.
Use 1 db request instead of 2.
Remove unused return value.

blueprint db-session-cleanup

Change-Id: I2c8252de7978e8fddd800e903f18a73ee9a95034

nova/db/sqlalchemy/api.py

@@ -4554,21 +4554,7 @@ def _ec2_instance_get_query(context, session=None):
 
 
 @require_admin_context
-def task_log_get(context, task_name, period_beginning,
+def _task_log_get_query(context, task_name, period_beginning,
-                 period_ending, host, state=None, session=None):
-    query = model_query(context, models.TaskLog, session=session).\
-                     filter_by(task_name=task_name).\
-                     filter_by(period_beginning=period_beginning).\
-                     filter_by(period_ending=period_ending).\
-                     filter_by(host=host)
-    if state is not None:
-        query = query.filter_by(state=state)
-
-    return query.first()
-
-
-@require_admin_context
-def task_log_get_all(context, task_name, period_beginning,
                         period_ending, host=None, state=None, session=None):
     query = model_query(context, models.TaskLog, session=session).\
                      filter_by(task_name=task_name).\
@@ -4578,25 +4564,34 @@ def task_log_get_all(context, task_name, period_beginning,
         query = query.filter_by(host=host)
     if state is not None:
         query = query.filter_by(state=state)
-    return query.all()
+    return query
 
 
 @require_admin_context
-def task_log_begin_task(context, task_name,
+def task_log_get(context, task_name, period_beginning, period_ending, host,
-                        period_beginning,
+                 state=None):
-                        period_ending,
+    return _task_log_get_query(task_name, period_beginning, period_ending,
-                        host,
+                               host, state).first()
-                        task_items=None,
+
-                        message=None,
+
-                        session=None):
+@require_admin_context
-    session = session or get_session()
+def task_log_get_all(context, task_name, period_beginning, period_ending,
+                     host=None, state=None):
+    return _task_log_get_query(task_name, period_beginning, period_ending,
+                               host, state).all()
+
+
+@require_admin_context
+def task_log_begin_task(context, task_name, period_beginning, period_ending,
+                        host, task_items=None, message=None):
+    # NOTE(boris-42): This method has a race condition and will be rewritten
+    #                 after bp/db-unique-keys implementation.
+    session = get_session()
     with session.begin():
-        task = task_log_get(context, task_name,
+        task_ref = _task_log_get_query(context, task_name, period_beginning,
-                            period_beginning,
+                                       period_ending, host, session=session).\
-                            period_ending,
+                        first()
-                            host,
+        if task_ref:
-                            session=session)
-        if task:
             #It's already run(ning)!
             raise exception.TaskAlreadyRunning(task_name=task_name, host=host)
         task = models.TaskLog()
@@ -4610,30 +4605,20 @@ def task_log_begin_task(context, task_name,
         if task_items:
             task.task_items = task_items
         task.save(session=session)
-    return task
 
 
 @require_admin_context
-def task_log_end_task(context, task_name,
+def task_log_end_task(context, task_name, period_beginning, period_ending,
-                        period_beginning,
+                      host, errors, message=None):
-                        period_ending,
+    values = dict(state="DONE", errors=errors)
-                        host,
+    if message:
-                        errors,
+        values["message"] = message
-                        message=None,
+
-                        session=None):
+    session = get_session()
-    session = session or get_session()
     with session.begin():
-        task = task_log_get(context, task_name,
+        rows = _task_log_get_query(context, task_name, period_beginning,
-                            period_beginning,
+                                       period_ending, host, session=session).\
-                            period_ending,
+                        update(values)
-                            host,
+        if rows == 0:
-                            session=session)
-        if not task:
             #It's not running!
             raise exception.TaskNotRunning(task_name=task_name, host=host)
-        task.state = "DONE"
-        if message:
-            task.message = message
-        task.errors = errors
-        task.save(session=session)
-    return task