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Enforce READ COMMITTED isolation when using mysql #15714

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merged 3 commits into from
May 9, 2021
Merged

Enforce READ COMMITTED isolation when using mysql #15714

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79adaa5
Enforce READ COMMITTED isolation when using mysql
SamWheating May 7, 2021
1aba800
Fixing up tests, removing indentation
SamWheating May 7, 2021
ef6e45d
Fixing test
SamWheating May 7, 2021
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9 changes: 9 additions & 0 deletions airflow/settings.py
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Original file line number Diff line number Diff line change
Expand Up @@ -287,6 +287,15 @@ def prepare_engine_args(disable_connection_pool=False):
engine_args['pool_recycle'] = pool_recycle
engine_args['pool_pre_ping'] = pool_pre_ping
engine_args['max_overflow'] = max_overflow

# The default isolation level for MySQL (REPEATABLE READ) can introduce inconsistencies when
# running multiple schedulers, as repeated queries on the same session may read from stale snapshots.
# 'READ COMMITTED' is the default value for PostgreSQL.
# More information here:
# https://dev.mysql.com/doc/refman/8.0/en/innodb-transaction-isolation-levels.html"
if SQL_ALCHEMY_CONN.startswith('mysql'):
engine_args['isolation_level'] = 'READ COMMITTED'

return engine_args


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5 changes: 5 additions & 0 deletions tests/core/test_sqlalchemy_config.py
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Expand Up @@ -57,6 +57,7 @@ def test_configure_orm_with_default_values(
pool_pre_ping=True,
pool_recycle=1800,
pool_size=5,
isolation_level='READ COMMITTED',
)

@patch('airflow.settings.setup_event_handlers')
Expand All @@ -75,11 +76,15 @@ def test_sql_alchemy_connect_args(
}
with conf_vars(config):
settings.configure_orm()
engine_args = {}
if settings.SQL_ALCHEMY_CONN.startswith('mysql'):
engine_args['isolation_level'] = 'READ COMMITTED'
mock_create_engine.assert_called_once_with(
settings.SQL_ALCHEMY_CONN,
connect_args=SQL_ALCHEMY_CONNECT_ARGS,
poolclass=NullPool,
encoding='utf-8',
**engine_args,
)

@patch('airflow.settings.setup_event_handlers')
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2 changes: 2 additions & 0 deletions tests/www/test_app.py
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Expand Up @@ -223,6 +223,8 @@ def debug_view():
def test_should_set_sqlalchemy_engine_options(self):
app = application.cached_app(testing=True)
engine_params = {'pool_size': 3, 'pool_recycle': 120, 'pool_pre_ping': True, 'max_overflow': 5}
if app.config['SQLALCHEMY_DATABASE_URI'].startswith('mysql'):
engine_params['isolation_level'] = 'READ COMMITTED'
assert app.config['SQLALCHEMY_ENGINE_OPTIONS'] == engine_params

@conf_vars(
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