Nominatim/test/python/test_db_async_connection.py
2021-05-19 23:07:39 +02:00

108 lines
2.8 KiB
Python

"""
Tests for function providing a non-blocking query interface towards PostgreSQL.
"""
from contextlib import closing
import concurrent.futures
import pytest
import psycopg2
from nominatim.db.async_connection import DBConnection, DeadlockHandler
@pytest.fixture
def conn(temp_db):
with closing(DBConnection('dbname=' + temp_db)) as connection:
yield connection
@pytest.fixture
def simple_conns(temp_db):
conn1 = psycopg2.connect('dbname=' + temp_db)
conn2 = psycopg2.connect('dbname=' + temp_db)
yield conn1.cursor(), conn2.cursor()
conn1.close()
conn2.close()
def test_simple_query(conn, temp_db_conn):
conn.connect()
conn.perform('CREATE TABLE foo (id INT)')
conn.wait()
temp_db_conn.table_exists('foo')
def test_wait_for_query(conn):
conn.connect()
conn.perform('SELECT pg_sleep(1)')
assert not conn.is_done()
conn.wait()
def test_bad_query(conn):
conn.connect()
conn.perform('SELECT efasfjsea')
with pytest.raises(psycopg2.ProgrammingError):
conn.wait()
def test_bad_query_ignore(temp_db):
with closing(DBConnection('dbname=' + temp_db, ignore_sql_errors=True)) as conn:
conn.connect()
conn.perform('SELECT efasfjsea')
conn.wait()
def exec_with_deadlock(cur, sql, detector):
with DeadlockHandler(lambda *args: detector.append(1)):
cur.execute(sql)
def test_deadlock(simple_conns):
cur1, cur2 = simple_conns
cur1.execute("""CREATE TABLE t1 (id INT PRIMARY KEY, t TEXT);
INSERT into t1 VALUES (1, 'a'), (2, 'b')""")
cur1.connection.commit()
cur1.execute("UPDATE t1 SET t = 'x' WHERE id = 1")
cur2.execute("UPDATE t1 SET t = 'x' WHERE id = 2")
# This is the tricky part of the test. The first SQL command runs into
# a lock and blocks, so we have to run it in a separate thread. When the
# second deadlocking SQL statement is issued, Postgresql will abort one of
# the two transactions that cause the deadlock. There is no way to tell
# which one of the two. Therefore wrap both in a DeadlockHandler and
# expect that exactly one of the two triggers.
with concurrent.futures.ThreadPoolExecutor(max_workers=1) as executor:
deadlock_check = []
try:
future = executor.submit(exec_with_deadlock, cur2,
"UPDATE t1 SET t = 'y' WHERE id = 1",
deadlock_check)
while not future.running():
pass
exec_with_deadlock(cur1, "UPDATE t1 SET t = 'y' WHERE id = 2",
deadlock_check)
finally:
# Whatever happens, make sure the deadlock gets resolved.
cur1.connection.rollback()
future.result()
assert len(deadlock_check) == 1