Created
September 4, 2020 16:37
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How to use PostgreSQL's LISTEN/NOTIFY as a simple message queue with psycopg2 and asyncio
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import asyncio | |
import psycopg2 | |
# dbname should be the same for the notifying process | |
conn = psycopg2.connect(host="localhost", dbname="example", user="example", password="example") | |
conn.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT) | |
cursor = conn.cursor() | |
cursor.execute(f"LISTEN match_updates;") | |
def handle_notify(): | |
conn.poll() | |
for notify in conn.notifies: | |
print(notify.payload) | |
conn.notifies.clear() | |
# It works with uvloop too: | |
# import uvloop | |
# loop = uvloop.new_event_loop() | |
# asyncio.set_event_loop(loop) | |
loop = asyncio.get_event_loop() | |
loop.add_reader(conn, handle_notify) | |
loop.run_forever() |
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import time | |
import psycopg2 | |
# dbname should be the same for the listening process | |
conn = psycopg2.connect(host="localhost", dbname="example", user="example", password="example") | |
cursor = conn.cursor() | |
conn.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT) | |
while True: | |
val = time.time() | |
cursor.execute(f"NOTIFY match_updates, '{val}';") | |
time.sleep(1) |
Thank you so much for the detailed reply!
It would be quite useful @kissgyorgy if you have time to make a similar gist for psycopg
version 3
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@d33tah You can call the pg_notify function instead of the NOTIFY directive. You should be able to do parameter substitution with psycopg2 then.