python 41 lines · 7 steps

Graceful shutdown in a queue worker

A worker loop that catches termination signals and exits only after the current task finishes.

Explained by highlit
Intermediate signals graceful-shutdown message-queue error-handling concurrency
1import signal
2import time
3import logging
4 
5logger = logging.getLogger("worker")
6 
7 
8class GracefulWorker:
9 def __init__(self, queue, poll_interval=1.0, visibility_timeout=30):
10 self.queue = queue
11 self.poll_interval = poll_interval
12 self.visibility_timeout = visibility_timeout
13 self._shutdown = False
14 
15 def _request_shutdown(self, signum, frame):
16 logger.info("received signal %s, finishing current task then exiting", signum)
17 self._shutdown = True
18 
19 def run(self):
20 signal.signal(signal.SIGTERM, self._request_shutdown)
21 signal.signal(signal.SIGINT, self._request_shutdown)
22 
23 while not self._shutdown:
24 message = self.queue.receive(wait_seconds=self.poll_interval)
25 if message is None:
26 continue
27 self._process(message)
28 
29 logger.info("worker stopped cleanly")
30 
31 def _process(self, message):
32 try:
33 self.handle(message.body)
34 except Exception:
35 logger.exception("task %s failed, leaving for redelivery", message.id)
36 self.queue.release(message)
37 else:
38 self.queue.ack(message)
39 
40 def handle(self, body):
41 raise NotImplementedError
01 / 01
STEP 01

Walkthrough

Space play ←→ step click any line
Three takeaways
  1. 1A shared flag lets a signal handler request shutdown without interrupting work mid-task.
  2. 2Acknowledge messages only on success so failures are redelivered instead of silently lost.
  3. 3Leaving handle unimplemented turns the class into a reusable base for concrete workers.

Related explainers

rust 
use serde::Deserialize;
 
#[derive(Debug, Deserialize)]
#[serde(untagged)]

Parsing flexible JSON shapes with serde

deserialization enums json
Intermediate 6 steps
ruby 
require "shellwords"
require "open3"
 
module Backup

Building safe shell commands in Ruby

shell-out subprocess command-injection
Intermediate 7 steps
python 
from fastapi import FastAPI, WebSocket, WebSocketDisconnect
 
app = FastAPI()
 

Building a WebSocket chat with FastAPI

websockets broadcast connection-management
Intermediate 9 steps
python 
import time
import uuid
 
from django.utils.deprecation import MiddlewareMixin

Attaching per-request context in Django

middleware request lifecycle multi-tenancy
Intermediate 7 steps
typescript 
import { Injectable, effect, signal, computed } from '@angular/core';
 
interface Preferences {
  theme: 'light' | 'dark';

A signal-based preferences store in Angular

signals state-management persistence
Intermediate 7 steps
go 
func (w *Watcher) resetDebounce(d time.Duration) {
	if !w.timer.Stop() {
		select {
		case <-w.timer.C:

Debouncing a stream of events in Go

debounce timers channels
Advanced 7 steps

Share this explainer

Here's the card — post it anywhere.

Graceful shutdown in a queue worker — share card
Made with highlit — turn any snippet into a walkthrough like this in about a minute.
Explain your code