database: Remove retry_on_conflict helper and default to autocommit

All our usage was of a single query anyway, so autocommit is easier to handle.
You can still opt into a longer transaction using the transaction() helper.
pull/45/head
Mike Lang 6 years ago committed by Christopher Usher
parent 73640ed4ab
commit 292188ad7c

@ -5,6 +5,8 @@ Note that this code requires psycopg2 and psycogreen, but the common module
as a whole does not to avoid needing to install them for components that don't need it.
"""
from contextlib import contextmanager
import psycopg2
import psycopg2.extensions
import psycopg2.extras
@ -70,16 +72,15 @@ class DBManager(object):
the initial conn used to apply the schema, and you should use a real conn pool for
any non-trivial use.
Returned conns are set to seralizable isolation level, and use NamedTupleCursor cursors.
Returned conns are set to seralizable isolation level, autocommit, and use NamedTupleCursor cursors.
"""
def __init__(self, **connect_kwargs):
patch_psycopg()
self.conns = []
self.connect_kwargs = connect_kwargs
conn = self.get_conn()
with conn:
with conn.cursor() as cur:
cur.execute(SCHEMA)
with transaction(conn):
query(conn, SCHEMA)
self.put_conn(conn)
def put_conn(self, conn):
@ -93,24 +94,23 @@ class DBManager(object):
# we don't care about the performance concerns and everything we do is easily retryable.
# This shouldn't matter in practice anyway since everything we're doing is either read-only
# searches or targetted single-row updates.
conn.set_session(psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE)
conn.isolation_level = psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE
conn.autocommit = True
return conn
def retry_on_conflict(conn, func, *args, **kwargs):
"""Run func(conn, *args, **kwargs) in a transaction up to max_tries (given as kwarg) times
(at least once, default 5), retrying if it raises an error indicating a transaction conflict.
After max_tries, raises TransactionRollbackError.
"""
max_tries = kwargs.pop('max_tries', 5)
for _ in range(max_tries - 1):
try:
with conn:
return func(conn)
except psycopg2.extensions.TransactionRollbackError:
pass
with conn:
return func(conn)
@contextmanager
def transaction(conn):
"""Helper context manager that runs the code block as a single database transaction
instead of in autocommit mode. The only difference between this and "with conn" is
that we explicitly disable then re-enable autocommit."""
old_autocommit = conn.autocommit
conn.autocommit = False
try:
with conn:
yield
finally:
conn.autocommit = old_autocommit
def query(conn, query, *args, **kwargs):

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