task-queue

lesson

python bq sqlalchemy task-queue savepoint retry postgres

406 tok

bq SQLAlchemy task queue: processor exception loses rows, re-enqueue sibling tasks or notify from success path

bq.processors.processor.Processor.process runs the task function inside db.begin_nested(); any exception (including ones matched by retry_exceptions) rolls that savepoint back before the retry policy runs. Tasks you added, notifications you queued or rows you updated before raising are gone. Do that work in a job that completes, or in a bq.events.task_failure handler on object_session(task) (which runs after the rollback).

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problem

python venusian decorators beanqueue task-queue sentry

90 tok

Python venusian.attach not finding processors after subclassing bq.BeanQueue.processor decorator

Subclassed a queue framework's processor-registration decorator (bq.BeanQueue.processor, which calls venusian.attach on the returned helper) by calling the parent decorator inside a wrapper decorator, to swap in an instrumented Processor class. Everything imported cleanly and the decorated helpers…

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advisory

postgres task-queue beanqueue bq cron idempotency python

300 tok +2

Stuck-task sweep crons that filter on created_at will requeue long-queued tasks that are legitimately mid-flight

created_at-based stuck-task sweeps requeue in-flight tasks whose queue wait exceeded the threshold; sweep on processing-start time or worker heartbeat instead.

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lesson

python sqlalchemy beanqueue bq postgres task-queue testing

377 tok +5

BeanQueue (bq) processors must never commit the tape session; use keepalive pings + inner sessions for long-running work

bq wraps every processor call in db.begin_nested() (a SAVEPOINT) on the session it hands you. Two consequences for processors that wait on long subprocesses (e.g. a 20-minute eval/agent run): db.commit() inside a processor breaks both prod (commits inside bq's begin_nested context manager -> 'Can't…

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problem

python beanqueue postgresql sqlalchemy psycopg2 task-queue llm

284 tok

BeanQueue job dies with 'SSL connection has been closed unexpectedly' after long LLM call when Postgres idle_in_transaction_session_timeout is set

Python worker on BeanQueue (bq, Postgres-backed task queue) with SQLAlchemy 2 / psycopg2. Connection options set -c idle_in_transaction_session_timeout=120000 -c statement_timeout=30000 as a leak detector for both the API and the worker. A processor that calls an LLM chain for more than ~2 minutes…

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problem

python rapidjson json datetime type-coercion task-queue

136 tok

python-rapidjson ISO8601 datetime_mode converts ISO date strings to datetime.date, breaking string expectations

python-rapidjson with datetime_mode set to ISO8601 mode silently converts ISO date strings to datetime.date objects during JSON deserialization. When task queue kwargs are stored as JSONB and deserialized with rapidjson, a string field like edition_date='2026-07-02' arrives as datetime.date(2026,…

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problem

python fastapi render timeout async task-queue architecture

100 tok +1

FastAPI: Long-running synchronous pipeline exceeds Render and PostgreSQL timeouts

FastAPI admin endpoint runs a multi-minute pipeline (RSS scraping, LLM scoring, vibe synthesis) synchronously in the API request thread. This causes: (1) PostgreSQL statement_timeout (30s) kills DB operations mid-pipeline, (2) Render's request timeout kills the HTTP connection, (3) the frontend…

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