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maximebeauchemin pushed a commit to branch master
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The following commit(s) were added to refs/heads/master by this push:
new cc36428 Modernize SQLA pessimistic handling (#3256)
cc36428 is described below
commit cc36428260f979d78e69d86dac0e6a4ba6b17780
Author: Maxime Beauchemin <maximebeauche...@gmail.com>
AuthorDate: Wed Aug 9 09:10:12 2017 -0700
Modernize SQLA pessimistic handling (#3256)
Looks like SQLAlchemy has redefined the best practice around
pessimistic connection handling.
---
superset/__init__.py | 2 +-
superset/utils.py | 49 ++++++++++++++++++++++++++++++++++++-------------
2 files changed, 37 insertions(+), 14 deletions(-)
diff --git a/superset/__init__.py b/superset/__init__.py
index fceff86..b8fccd9 100644
--- a/superset/__init__.py
+++ b/superset/__init__.py
@@ -69,7 +69,7 @@ db = SQLA(app)
if conf.get('WTF_CSRF_ENABLED'):
csrf = CSRFProtect(app)
-utils.pessimistic_connection_handling(db.engine.pool)
+utils.pessimistic_connection_handling(db.engine)
cache = utils.setup_cache(app, conf.get('CACHE_CONFIG'))
tables_cache = utils.setup_cache(app, conf.get('TABLE_NAMES_CACHE_CONFIG'))
diff --git a/superset/utils.py b/superset/utils.py
index 49a0f47..ed84186 100644
--- a/superset/utils.py
+++ b/superset/utils.py
@@ -40,7 +40,7 @@ from flask_babel import gettext as __
import markdown as md
from past.builtins import basestring
from pydruid.utils.having import Having
-from sqlalchemy import event, exc
+from sqlalchemy import event, exc, select
from sqlalchemy.types import TypeDecorator, TEXT
logging.getLogger('MARKDOWN').setLevel(logging.INFO)
@@ -436,19 +436,42 @@ class timeout(object):
logging.warning("timeout can't be used in the current context")
logging.exception(e)
-def pessimistic_connection_handling(target):
- @event.listens_for(target, "checkout")
- def ping_connection(dbapi_connection, connection_record, connection_proxy):
- """
- Disconnect Handling - Pessimistic, taken from:
- http://docs.sqlalchemy.org/en/rel_0_9/core/pooling.html
- """
- cursor = dbapi_connection.cursor()
+
+def pessimistic_connection_handling(some_engine):
+ @event.listens_for(some_engine, "engine_connect")
+ def ping_connection(connection, branch):
+ if branch:
+ # "branch" refers to a sub-connection of a connection,
+ # we don't want to bother pinging on these.
+ return
+
+ # turn off "close with result". This flag is only used with
+ # "connectionless" execution, otherwise will be False in any case
+ save_should_close_with_result = connection.should_close_with_result
+ connection.should_close_with_result = False
+
try:
- cursor.execute("SELECT 1")
- except:
- raise exc.DisconnectionError()
- cursor.close()
+ # run a SELECT 1. use a core select() so that
+ # the SELECT of a scalar value without a table is
+ # appropriately formatted for the backend
+ connection.scalar(select([1]))
+ except exc.DBAPIError as err:
+ # catch SQLAlchemy's DBAPIError, which is a wrapper
+ # for the DBAPI's exception. It includes a .connection_invalidated
+ # attribute which specifies if this connection is a "disconnect"
+ # condition, which is based on inspection of the original exception
+ # by the dialect in use.
+ if err.connection_invalidated:
+ # run the same SELECT again - the connection will re-validate
+ # itself and establish a new connection. The disconnect
detection
+ # here also causes the whole connection pool to be invalidated
+ # so that all stale connections are discarded.
+ connection.scalar(select([1]))
+ else:
+ raise
+ finally:
+ # restore "close with result"
+ connection.should_close_with_result = save_should_close_with_result
class QueryStatus(object):
--
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