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POHow to fail the chain if it's sub task gives an exception
 

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  1. POHow to fail the chain if it's sub task gives an exception
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    <p>I have faced a pretty strange issue with celery:</p> <p>There is a chain of tasks, and one of them gives an exception and does several retries</p> <pre><code>chain = (err.si(1) | err.si(2)) result = chain.apply_async() result.state result.get() </code></pre> <p>here is the code of the task:</p> <pre><code>@celery.task(base=MyTask) def err(x): try: if x &lt; 3: raise Exception else: return x+1 except Exception as exp: print "retrying" raise err.retry(args=[x],exc=exp,countdown=5,max_retries=3) </code></pre> <p>The thing is that although the task in chain gives an exception, but the result.state keeps being 'PENDING' and .get() just freezes.</p> <p>I have tried to fail the task in case it reaches maximum retries value:</p> <pre><code>class MyTask(celery.Task): abstract = True def after_return(self, status, retval, task_id, args, kwargs, einfo): if self.max_retries == self.request.retries: self.state = states.FAILURE </code></pre> <p>But although executed separately task is getting marked as FAILED, executing in chain gives same result - PENDING &amp; Freezed get.</p> <p>I expected that the chain will get failed once any of it's tasks will get failed and .get of the result should produce the exception thrown from the task.</p> <p>_<strong><em>UPDATE</em>_</strong> Stack trace given by apply_async with ALWAYS_EAGER=True</p> <pre><code>result = chain.apply_async() Exception Traceback (most recent call last) &lt;ipython-input-4-81202b369b5f&gt; in &lt;module&gt;() ----&gt; 1 result = chain.apply_async() lib/python2.7/site-packages/celery/canvas.pyc in apply_async(self, args, kwargs, **options) 147 # For callbacks: extra args are prepended to the stored args. 148 args, kwargs, options = self._merge(args, kwargs, options) --&gt; 149 return self.type.apply_async(args, kwargs, **options) 150 151 def append_to_list_option(self, key, value): /lib/python2.7/site-packages/celery/app/builtins.pyc in apply_async(self, args, kwargs, group_id, chord, task_id, **options) 232 task_id=None, **options): 233 if self.app.conf.CELERY_ALWAYS_EAGER: --&gt; 234 return self.apply(args, kwargs, **options) 235 options.pop('publisher', None) 236 tasks, results = self.prepare_steps(args, kwargs['tasks']) lib/python2.7/site-packages/celery/app/builtins.pyc in apply(self, args, kwargs, subtask, **options) 249 last, fargs = None, args # fargs passed to first task only 250 for task in kwargs['tasks']: --&gt; 251 res = subtask(task).clone(fargs).apply(last and (last.get(), )) 252 res.parent, last, fargs = last, res, None 253 return last lib/python2.7/site-packages/celery/result.pyc in get(self, timeout, propagate, **kwargs) 677 elif self.state in states.PROPAGATE_STATES: 678 if propagate: --&gt; 679 raise self.result 680 return self.result 681 wait = get Exception: </code></pre>
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    1. USAlex Luberg
    1. USAlex Luberg
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      1. VTUpMod
    1. COTry running your task with CELERY_ALWAYS_EAGER activated , that should help you find out what is causing the issue.
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      1. POHow to fail the chain if it's sub task gives an exception
      1. USThomas Orozco
    2. COIn case I have CELERY_ALWAYS_EAGER set to True, apply_async immediately gives the stack trace and the results var is None. In case I have it set to false, the result does exist with result.state = Pending.
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      1. USAlex Luberg
 

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