rust/neon
1
0
Fork 0
mirror of https://github.com/neondatabase/neon.git synced 2026-01-06 04:52:55 +00:00
Code Issues Packages Projects Releases Wiki Activity

Fix autocommit footguns in performance tests

Browse Source 
psycopg2 has the following warning related to autocommit:

> By default, any query execution, including a simple SELECT will start
> a transaction: for long-running programs, if no further action is
> taken, the session will remain “idle in transaction”, an undesirable
> condition for several reasons (locks are held by the session, tables
> bloat…). For long lived scripts, either ensure to terminate a
> transaction as soon as possible or use an autocommit connection.

In the 2.9 release notes, psycopg2 also made the following change:

> `with connection` starts a transaction on autocommit transactions too

Some of these connections are indeed long-lived, so we were retaining
tons of WAL on the endpoints because we had a transaction pinned in the
past.

Link: https://www.psycopg.org/docs/news.html#what-s-new-in-psycopg-2-9
Link: https://github.com/psycopg/psycopg2/issues/941
Signed-off-by: Tristan Partin <tristan@neon.tech>
This commit is contained in:
Tristan Partin
2024-11-12 15:48:19 -06:00
committed by GitHub
parent 2256a5727a
commit d8f5d43549
2 changed files with 98 additions and 74 deletions
Download Patch File Download Diff File Expand all files Collapse all files

61
test_runner/performance/test_physical_replication.py
View File

@@ -102,15 +102,21 @@ def test_ro_replica_lag(
check_pgbench_still_running(master_workload)
check_pgbench_still_running(replica_workload)
time.sleep(sync_interval_min * 60)
conn_master = psycopg2.connect(master_connstr)
conn_replica = psycopg2.connect(replica_connstr)
conn_master.autocommit = True
conn_replica.autocommit = True
with (
psycopg2.connect(master_connstr) as conn_master,
psycopg2.connect(replica_connstr) as conn_replica,
conn_master.cursor() as cur_master,
conn_replica.cursor() as cur_replica,
):
with (
conn_master.cursor() as cur_master,
conn_replica.cursor() as cur_replica,
):
lag = measure_replication_lag(cur_master, cur_replica)
lag = measure_replication_lag(cur_master, cur_replica)
conn_master.close()
conn_replica.close()
log.info(f"Replica lagged behind master by {lag} seconds")
zenbenchmark.record("replica_lag", lag, "s", MetricReport.LOWER_IS_BETTER)
finally:
@@ -219,11 +225,15 @@ def test_replication_start_stop(
pg_bin.run_capture(["pgbench", "-i", "-I", "dtGvp", "-s10"], env=master_env)
# Sync replicas
with psycopg2.connect(master_connstr) as conn_master:
with conn_master.cursor() as cur_master:
for i in range(num_replicas):
conn_replica = psycopg2.connect(replica_connstr[i])
measure_replication_lag(cur_master, conn_replica.cursor())
conn_master = psycopg2.connect(master_connstr)
conn_master.autocommit = True
with conn_master.cursor() as cur_master:
for i in range(num_replicas):
conn_replica = psycopg2.connect(replica_connstr[i])
measure_replication_lag(cur_master, conn_replica.cursor())
conn_master.close()
master_pgbench = pg_bin.run_nonblocking(
[
@@ -277,17 +287,22 @@ def test_replication_start_stop(
time.sleep(configuration_test_time_sec)
with psycopg2.connect(master_connstr) as conn_master:
with conn_master.cursor() as cur_master:
for ireplica in range(num_replicas):
replica_conn = psycopg2.connect(replica_connstr[ireplica])
lag = measure_replication_lag(cur_master, replica_conn.cursor())
zenbenchmark.record(
f"Replica {ireplica} lag", lag, "s", MetricReport.LOWER_IS_BETTER
)
log.info(
f"Replica {ireplica} lagging behind master by {lag} seconds after configuration {iconfig:>b}"
)
conn_master = psycopg2.connect(master_connstr)
conn_master.autocommit = True
with conn_master.cursor() as cur_master:
for ireplica in range(num_replicas):
replica_conn = psycopg2.connect(replica_connstr[ireplica])
lag = measure_replication_lag(cur_master, replica_conn.cursor())
zenbenchmark.record(
f"Replica {ireplica} lag", lag, "s", MetricReport.LOWER_IS_BETTER
)
log.info(
f"Replica {ireplica} lagging behind master by {lag} seconds after configuration {iconfig:>b}"
)
conn_master.close()
master_pgbench.terminate()
except Exception as e:
error_occurred = True