Background Cleanup¶

psycache ignores expired keys when reading, but their rows stick around until something deletes them. You can call PostgresCache.cleanup_expired() yourself, or let psycache do it for you in the background.

A cleanup thread¶

For synchronous pools, PostgresCache.start_cleanup_thread() starts a daemon thread that periodically deletes expired entries. Use it as a context manager to stop the thread automatically:

from sqlalchemy import create_engine

from psycache import PostgresCache
from psycache.sqlalchemy import SQLAlchemyCachePool


engine = create_engine("postgresql+psycopg://psycache@127.0.0.1/psycache")
cache = PostgresCache(SQLAlchemyCachePool(engine))


with cache.start_cleanup_thread(interval=60):
    ...  # your application runs here

Or manage its lifecycle manually through the returned CleanupService:

svc = cache.start_cleanup_thread(interval=60)
try:
    ...  # your application runs here
finally:
    svc.stop()

engine.dispose()

… or a cleanup task¶

For async pools, use AsyncPostgresCache.start_cleanup_task() inside a running event loop. It starts an asyncio.Task that periodically deletes expired entries and can be used as an async context manager.

Otherwise, it mirrors the behavior of PostgresCache.start_cleanup_thread():

import asyncio

from sqlalchemy.ext.asyncio import create_async_engine

from psycache import AsyncPostgresCache
from psycache.sqlalchemy import AsyncSQLAlchemyCachePool


aengine = create_async_engine("postgresql+psycopg://psycache@127.0.0.1/psycache")
acache = AsyncPostgresCache(AsyncSQLAlchemyCachePool(aengine))

async def main():
    async with acache.start_cleanup_task(interval=60):
        ...  # your application runs here

    svc = acache.start_cleanup_task(interval=60)
    try:
        ...  # your application runs here
    finally:
        await svc.stop()

asyncio.run(main())