What is the meaning of bind = True keyword in celery?

Question

What is the meaning of bind=True in below celery code? When to use it and when not?

@app.task(bind=True) def send_twitter_status(self, oauth, tweet):     try:         twitter = Twitter(oauth)         twitter.update_status(tweet)     except (Twitter.FailWhaleError, Twitter.LoginError) as exc:         raise self.retry(exc=exc) 

Answer 1

Just a small addition to other answers. As already stated, bound tasks have access to the task instance. One use case when this is needed are retries:

@celery.task(bind=True, max_retries=5) def retrying(self):     try:         return 1/0     except Exception:         self.retry(countdown=5) 

Another use case is when you want to define custom states for your tasks and be able to set it during task execution:

@celery.task(bind=True) def show_progress(self, n):     for i in range(n):         self.update_state(state='PROGRESS', meta={'current': i, 'total': n}) 

Answer 2

Bound tasks

A task being bound means the first argument to the task will always be the task instance (self), just like Python bound methods:

logger = get_task_logger(__name__)  @task(bind=True) def add(self, x, y):     logger.info(self.request.id)