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POAppEngine: gaierror when starting a task
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copied!<p>I ran into an error that was painful to track down, so I thought I'd add the cause + "solution" here. </p> <p>The setup: Devbox - Running Google App Engine listening on all ports ("--address=0.0.0.0") serving a URL that launches a task. Client - Client (Python requests library) which queries the callback URL</p> <p>App Engine code:</p> <pre><code>class StartTaskCallback(webapp.RequestHandler): def post(self): param = self.request.get('param') logging.info('STARTTASK: %s' % param) # launch a task taskqueue.add(url='/tasks/mytask', queue_name='myqueue', params={'param': param}) class MyTask(webapp.RequestHandler): def post(self): param = self.request.get('param') logging.info('MYTASK: param = %s' % param) </code></pre> <p>When I queried the callback with my browser, everything worked, but the same query from the remote client gave me the following error:</p> <pre><code>ERROR 2012-03-23 21:18:27,351 taskqueue_stub.py:1858] An error occured while sending the task "task1" (Url: "/tasks/mytask") in queue "myqueue". Treating as a task error. Traceback (most recent call last): File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/taskqueue/taskqueue_stub.py", line 1846, in ExecuteTask connection.endheaders() File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/httplib.py", line 868, in endheaders self._send_output() File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/httplib.py", line 740, in _send_output self.send(msg) File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/httplib.py", line 699, in send self.connect() File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/httplib.py", line 683, in connect self.timeout) File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 498, in create_connection for res in getaddrinfo(host, port, 0, SOCK_STREAM): gaierror: [Errno 8] nodename nor servname provided, or not known </code></pre> <p>This error would just spin in a loop as the task retried. Though oddly, I could go to Admin -> Task Queues and click 'Run' to get the task to complete successfully.</p> <p>At first I thought this was an error with the binding. I would not get an error if I queried the StartTaskCallback via the browser or if I ran the client locally.</p> <p>Finally I noticed that App Engine is using the 'host' field of the request in order to build an absolute URL for the task. In /Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/taskqueue/taskqueue_stub.py (1829):</p> <pre><code> connection_host, = header_dict.get('host', [self._default_host]) if connection_host is None: logging.error('Could not determine where to send the task "%s" ' '(Url: "%s") in queue "%s". Treating as an error.', task.task_name(), task.url(), queue.queue_name) return False connection = httplib.HTTPConnection(connection_host) </code></pre> <p>In my case, I was using a special name + hosts file on the remote client to access the server. 192.168.1.208 devbox So the 'host' for the remote client looked like 'devbox:8085' which the local server could not resolve.</p>

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