fix: implement libpq semantic for target_session_attrs=prefer-standby#1022
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fix: implement libpq semantic for target_session_attrs=prefer-standby#1022
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First attempt all the servers in standby mode, then fall back to any mode. Fix #1021.
Member
Author
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Note: there are both connection tests to verify that the libpq filters the right server (within reason: we only test with a primary server) and unittest level to verify that the attamps made in |
Only one test fails with the currently "oldest" libpq, which is 10.2, however the docs in libpq 13 are not explicit in which modes are supported and, afaics, 'replica' shouldn't work either. https://www.postgresql.org/docs/13/libpq-connect.html
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This is looking good to me so far. Using the below code to test. Have not looked as async yet though, can take a closer look tommorow. import psycopg
import pytest
def test(hosts: str, ports: str, target_session_attrs: str, expected_port: int) -> None:
print(target_session_attrs)
# Connect to an existing database
if expected_port:
with psycopg.connect(f"host={hosts} port={ports} dbname=postgres user=andrew target_session_attrs={target_session_attrs}") as conn:
# Open a cursor to perform database operations
with conn.cursor() as cur:
cur.execute("select setting from pg_settings where name = 'port'")
port = cur.fetchone()[0]
assert expected_port == int(port)
else:
with pytest.raises(Exception):
psycopg.connect(
f"host={hosts} port={ports} dbname=postgres user=andrew target_session_attrs={target_session_attrs}")
def test_all() -> None:
test(hosts="localhost,localhost", ports="5432,5433",
target_session_attrs="primary", expected_port=5432)
test(hosts="localhost,localhost", ports="5432,5433",
target_session_attrs="read-write", expected_port=5432)
test(hosts="localhost,localhost", ports="5432,5433",
target_session_attrs="standby", expected_port=5433)
test(hosts="localhost,localhost", ports="5432,5433",
target_session_attrs="prefer-standby", expected_port=5433)
test(hosts="localhost,localhost", ports="5432,5433",
target_session_attrs="read-only", expected_port=5433)
test(hosts="localhost", ports="5432",
target_session_attrs="primary", expected_port=5432)
test(hosts="localhost", ports="5432",
target_session_attrs="read-write", expected_port=5432)
test(hosts="localhost", ports="5432",
target_session_attrs="standby", expected_port=None)
test(hosts="localhost", ports="5432",
target_session_attrs="prefer-standby", expected_port=5432)
test(hosts="localhost", ports="5432",
target_session_attrs="read-only", expected_port=None)
test(hosts="localhost", ports="5433",
target_session_attrs="primary", expected_port=None)
test(hosts="localhost", ports="5433",
target_session_attrs="read-write", expected_port=None)
test(hosts="localhost", ports="5433",
target_session_attrs="standby", expected_port=5433)
test(hosts="localhost", ports="5433",
target_session_attrs="prefer-standby", expected_port=5433)
test(hosts="localhost", ports="5433",
target_session_attrs="read-only", expected_port=5433)
if __name__ == "__main__":
test_all() |
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Thank you very much for implementing this fix. Looking forward to the next release. |
Member
Author
|
@AndrewJackson2020 no worries and thank you for the report and fix proposal! Psycopg 3.2.6 with this fix will hit PyPI in a few minutes! |
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First attempt all the servers in standby mode, then fall back to any mode.
Fix #1021.
CC. @AndrewJackson2020