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feat(database): Engine-level Write-Ahead Logging & concurrency buffers for SQLite (#477) #486

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feat(database): Engine-level Write-Ahead Logging & concurrency buffers for SQLite (#477) #486

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21 changes: 20 additions & 1 deletion montage/app.py
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,17 @@ def set_mysql_session_charset_and_collation(connection, branch):
return


def set_sqlite_pragma(dbapi_connection, connection_record):
# @ayushshukla1807: Intercepting the raw dialect connection natively here to enforce WAL mode.
# This physically overrides the default DELETE journal locks and completely eliminates
# the 'Database is Locked' queue drops during our concurrent testing loops (#477).
cursor = dbapi_connection.cursor()
cursor.execute("PRAGMA journal_mode=WAL")
cursor.execute("PRAGMA synchronous=NORMAL")
cursor.execute("PRAGMA busy_timeout=5000")
cursor.close()


def create_app(env_name='prod', config=None):
# rendering is handled by MessageMiddleware
ui_routes = (PUBLIC_UI_ROUTES + JUROR_UI_ROUTES
Expand All @@ -68,7 +79,13 @@ def create_app(env_name='prod', config=None):
config = load_env_config(env_name=env_name)
print('== loaded config file: %s' % (config['__file__'],))

engine = create_engine(config.get('db_url', DEFAULT_DB_URL), pool_recycle=60)
db_url = config.get('db_url', DEFAULT_DB_URL)
engine = create_engine(db_url, pool_recycle=60)

if 'sqlite' in db_url:
event.listen(engine, 'connect', set_sqlite_pragma)
elif 'mysql' in db_url:
event.listen(engine, 'engine_connect', set_mysql_session_charset_and_collation)
session_type = sessionmaker()
session_type.configure(bind=engine)
tmp_rdb_session = session_type()
Expand Down Expand Up @@ -122,6 +139,8 @@ def get_engine():

if 'mysql' in db_url:
event.listen(engine, 'engine_connect', set_mysql_session_charset_and_collation)
elif 'sqlite' in db_url:
event.listen(engine, 'connect', set_sqlite_pragma)

return engine

Expand Down