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How do you deal with an exception raised by celery (not your code)?

So in my flask app right now I am using Celery to deploy servers on remote machines. Right now, I have an enum, status, which indicates the lifecycle of my deployment process:
#celery.task(bind=True)
def deploy_server(self, server_id):
server = Server.query.get(server_id)
if not server.can_launch():
return
try:
server.status = RemoteStatus.LAUNCHING
db.session.commit()
verify_DNS(server)
host = server.server.ssh_user + '#' + server.server.ip
execute(fabric_deploy_server, self, server, hosts=host)
server.status = RemoteStatus.LAUNCHED
db.session.commit()
except Exception as e:
server.status = RemoteStatus.ERROR
db.session.commit()
traceback.print_exc()
raise e
As you can see, when a server is being deployed, its status is changed to "Launching". If there is an exception, it will be changed to ERROR.
I found one exception which completely bypasses this bloc of code: when I overloaded my celery server with too many requests, I get this exception:
[2017-07-09 18:00:03,127: WARNING/PoolWorker-3] /app/.heroku/python/lib/python2.7/site-packages/celery/app/trace.py:542: RuntimeWarning: Exception raised outside body: ConnectionError('max number of clients reached',):
Traceback (most recent call last):
File "/app/.heroku/python/lib/python2.7/site-packages/celery/app/trace.py", line 427, in trace_task
uuid, retval, task_request, publish_result,
File "/app/.heroku/python/lib/python2.7/site-packages/celery/backends/base.py", line 152, in mark_as_done
self.store_result(task_id, result, state, request=request)
File "/app/.heroku/python/lib/python2.7/site-packages/celery/backends/base.py", line 309, in store_result
request=request, **kwargs)
File "/app/.heroku/python/lib/python2.7/site-packages/celery/backends/base.py", line 652, in _store_result
self.set(self.get_key_for_task(task_id), self.encode(meta))
File "/app/.heroku/python/lib/python2.7/site-packages/celery/backends/redis.py", line 204, in set
return self.ensure(self._set, (key, value), **retry_policy)
File "/app/.heroku/python/lib/python2.7/site-packages/celery/backends/redis.py", line 194, in ensure
**retry_policy)
File "/app/.heroku/python/lib/python2.7/site-packages/kombu/utils/functional.py", line 333, in retry_over_time
return fun(*args, **kwargs)
File "/app/.heroku/python/lib/python2.7/site-packages/celery/backends/redis.py", line 213, in _set
pipe.execute()
File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2641, in execute
return execute(conn, stack, raise_on_error)
File "/app/.heroku/python/lib/python2.7/site-packages/redis/client.py", line 2495, in _execute_transaction
connection.send_packed_command(all_cmds)
File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 538, in send_packed_command
self.connect()
File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 446, in connect
self.on_connect()
File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 514, in on_connect
if nativestr(self.read_response()) != 'OK':
File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 577, in read_response
response = self._parser.read_response()
File "/app/.heroku/python/lib/python2.7/site-packages/redis/connection.py", line 255, in read_response
raise error
ConnectionError: max number of clients reached
exc, exc_info.traceback)))
My biggest problem with this is that this error is raised somewhere outside of my Try/Catch bloc. Hence, when this exception occurs, all my servers remain in the "Launching" mode rather than "Error".
How can I catch this exception and modify Server.status?

In redis 2.4 there is a hard coded limit of max number of connections which is 10,000. In redis 2.6+ you can specify the max number of clients in redis.conf. also this is not a problem of celery your broker redis refused to accept connections that's the problem.
Set the max number of clients that can be handled by redis simultaneously using redis CLI. Check out redis clients

google-api-python-client broken because of OAuth2?

I am trying to check if a certain dataset exists in bigquery using the Google Api Client in Python. It always worked untill the last update where I got this strange error I don't know how to fix:
Traceback (most recent call last):
File "/root/miniconda/lib/python2.7/site-packages/dsUtils/bq_utils.py", line 106, in _get
resp = bq_service.datasets().get(projectId=self.project_id, datasetId=self.id).execute(num_retries=2)
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/util.py", line 140, in positional_wrapper
return wrapped(*args, **kwargs)
File "/root/miniconda/lib/python2.7/site-packages/googleapiclient/http.py", line 755, in execute
method=str(self.method), body=self.body, headers=self.headers)
File "/root/miniconda/lib/python2.7/site-packages/googleapiclient/http.py", line 93, in _retry_request
resp, content = http.request(uri, method, *args, **kwargs)
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/client.py", line 598, in new_request
self._refresh(request_orig)
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/client.py", line 864, in _refresh
self._do_refresh_request(http_request)
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/client.py", line 891, in _do_refresh_request
body = self._generate_refresh_request_body()
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/client.py", line 1597, in _generate_refresh_req
uest_body
assertion = self._generate_assertion()
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/service_account.py", line 263, in _generate_ass
ertion
key_id=self._private_key_id)
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/crypt.py", line 97, in make_signed_jwt
signature = signer.sign(signing_input)
File "/root/miniconda/lib/python2.7/site-packages/oauth2client/_pycrypto_crypt.py", line 101, in sign
return PKCS1_v1_5.new(self._key).sign(SHA256.new(message))
File "/root/miniconda/lib/python2.7/site-packages/Crypto/Signature/PKCS1_v1_5.py", line 112, in sign
m = self._key.decrypt(em)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/PublicKey/RSA.py", line 174, in decrypt
return pubkey.pubkey.decrypt(self, ciphertext)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/PublicKey/pubkey.py", line 93, in decrypt
plaintext=self._decrypt(ciphertext)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/PublicKey/RSA.py", line 235, in _decrypt
r = getRandomRange(1, self.key.n-1, randfunc=self._randfunc)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/Util/number.py", line 123, in getRandomRange
value = getRandomInteger(bits, randfunc)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/Util/number.py", line 104, in getRandomInteger
S = randfunc(N>>3)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 202, in read
return self._singleton.read(bytes)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 178, in read
return _UserFriendlyRNG.read(self, bytes)
File "/root/miniconda/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 137, in read
self._check_pid()
File "/root/miniconda/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 153, in _check_pid
raise AssertionError("PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()")
AssertionError: PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()
Is someone understanding what is hapening?
Note that I also get this error with other bricks like GCStorage.
Note also that I use the following command to load my Google credentials:
from oauth2client.client import GoogleCredentials
def get_credentials(credentials_path): #my json credentials path
logger.info('Getting credentials...')
try:
os.environ['GOOGLE_APPLICATION_CREDENTIALS'] = credentials_path
credentials = GoogleCredentials.get_application_default()
return credentials
except Exception as e:
raise e
So if anyone know a better way to load my google credentials using my json service account file, and which would avoid the error, please tell me.

It looks like the error is in the PyCrypto module, which appears to be used under the hood by Google's OAuth2 implementation. If your code is calling os.fork() at some point, you may need to call Crypto.Random.atfork() afterward in both the parent and child process in order to update the module's internal state.
See here for PyCrypto docs; search for "atfork" for more info:
https://github.com/dlitz/pycrypto
This question and answer might also be relevant:
PyCrypto : AssertionError("PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()")

How to catch exception for which the name is not defined in context?

I am seeing the python-requests library crash with the following traceback:
Traceback (most recent call last):
File "/usr/lib/python3.2/http/client.py", line 529, in _read_chunked
chunk_left = int(line, 16)
ValueError: invalid literal for int() with base 16: b''
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "./app.py", line 507, in getUrlContents
response = requests.get(url, headers=headers, auth=authCredentials, timeout=http_timeout_seconds)
File "/home/dotancohen/code/lib/requests/api.py", line 55, in get
return request('get', url, **kwargs)
File "/home/dotancohen/code/lib/requests/api.py", line 44, in request
return session.request(method=method, url=url, **kwargs)
File "/home/dotancohen/code/lib/requests/sessions.py", line 338, in request
resp = self.send(prep, **send_kwargs)
File "/home/dotancohen/code/lib/requests/sessions.py", line 441, in send
r = adapter.send(request, **kwargs)
File "/home/dotancohen/code/lib/requests/adapters.py", line 340, in send
r.content
File "/home/dotancohen/code/lib/requests/models.py", line 601, in content
self._content = bytes().join(self.iter_content(CONTENT_CHUNK_SIZE)) or bytes()
File "/home/dotancohen/code/lib/requests/models.py", line 542, in generate
for chunk in self.raw.stream(chunk_size, decode_content=True):
File "/home/dotancohen/code/lib/requests/packages/urllib3/response.py", line 222, in stream
data = self.read(amt=amt, decode_content=decode_content)
File "/home/dotancohen/code/lib/requests/packages/urllib3/response.py", line 173, in read
data = self._fp.read(amt)
File "/usr/lib/python3.2/http/client.py", line 489, in read
return self._read_chunked(amt)
File "/usr/lib/python3.2/http/client.py", line 534, in _read_chunked
raise IncompleteRead(b''.join(value))
http.client.IncompleteRead: IncompleteRead(0 bytes read)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/usr/lib/python3.2/threading.py", line 740, in _bootstrap_inner
self.run()
File "./app.py", line 298, in run
self.target(*self.args)
File "./app.py", line 400, in provider_query
url_contents = getUrlContents(str(providerUrl), '', authCredentials)
File "./app.py", line 523, in getUrlContents
except http.client.IncompleteRead as error:
NameError: global name 'http' is not defined
As can be seen, I've tried to catch the http.client.IncompleteRead: IncompleteRead(0 bytes read) error that requests is throwing with the line except http.client.IncompleteRead as error:. However, that is throwing a NameError due to http not being defined. So how can I catch that exception?
This is the code throwing the exception:
import requests
from requests_oauthlib import OAuth1
authCredentials = OAuth1('x', 'x', 'x', 'x')
response = requests.get(url, auth=authCredentials, timeout=20)
Note that I am not including the http library, though requests is including it. The error is very intermittent (happens perhaps once every few hours, even if I run the requests.get() command every ten seconds) so I'm not sure if added the http library to the imports has helped or not.
In any case, in the general sense, if included library A in turn includes library B, is it impossible to catch exceptions from B without including B myself?

To answer your question
In any case, in the general sense, if included library A in turn includes library B, is it impossible to catch exceptions from B without including B myself?
Yes. For example:
a.py:
import b
# do some stuff with b
c.py:
import a
# but you want to use b
a.b # gives you full access to module b which was imported by a
Although this does the job, it doesn't look so pretty, especially with long package/module/class/function names in real world.
So in your case to handle http exception, either try to figure out which package/module within requests imports http and so that you'd do raise requests.XX.http.WhateverError or rather just import it as http is a standard library.

It's hard to analyze the problem if you don't give source and just the stout,
but check this link out : http://docs.python-requests.org/en/latest/user/quickstart/#errors-and-exceptions
Basically,
try and catch the exception whereever the error is rising in your code.
Exceptions:
In the event of a network problem (e.g. DNS failure, refused connection, etc),
Requests will raise a **ConnectionError** exception.
In the event of the rare invalid HTTP response,
Requests will raise an **HTTPError** exception.
If a request times out, a **Timeout** exception is raised.
If a request exceeds the configured number of maximum redirections,
a **TooManyRedirects** exception is raised.
All exceptions that Requests explicitly raises inherit
from **requests.exceptions.RequestException.**
Hope that helped.

Python BaseHTTPServer, how do I catch/trap "broken pipe" errors?

I build a short url translator engine in Python, and I'm seeing a TON of "broken pipe" errors, and I'm curious how to trap it best when using the BaseHTTPServer classes. This isn't the entire code, but gives you an idea of what I'm doing so far:
from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer
import memcache
class clientThread(BaseHTTPRequestHandler):
def do_GET(self):
content = None
http_code,response_txt,long_url = \
self.ag_trans_url(self.path,content,'GET')
self.http_output( http_code, response_txt, long_url )
return
def http_output(self,http_code,response_txt,long_url):
self.send_response(http_code)
self.send_header('Content-type','text/plain')
if long_url:
self.send_header('Location', long_url)
self.end_headers()
if response_txt:
self.wfile.write(response_txt)
return
def ag_trans_url(self, orig_short_url, post_action, getpost):
short_url = 'http://foo.co' + orig_short_url
# fetch it from memcache
long_url = mc.get(short_url)
# other magic happens to look it up from db if there was nothing
# in memcache, etc
return (302, None, log_url)
def populate_memcache()
# connect to db, do lots of mc.set() calls
def main():
populate_memcache()
try:
port = 8001
if len(sys.argv) > 1:
port = int(sys.argv[1])
server = HTTPServer(('',port), clientThread)
#server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
print '[',str(datetime.datetime.now()),'] short url processing has begun'
server.serve_forever()
except KeyboardInterrupt,SystemExit:
print '^C received, shutting down server'
server.socket.close()
The code itself works great, but started throwing errors almost immediately when in production:
Traceback (most recent call last):
File "/usr/lib/python2.5/SocketServer.py", line 222, in handle_request
self.process_request(request, client_address)
File "/usr/lib/python2.5/SocketServer.py", line 241, in process_request
self.finish_request(request, client_address)
File "/usr/lib/python2.5/SocketServer.py", line 254, in finish_request
self.RequestHandlerClass(request, client_address, self)
File "/usr/lib/python2.5/SocketServer.py", line 522, in __init__
self.handle()
File "/usr/lib/python2.5/BaseHTTPServer.py", line 316, in handle
self.handle_one_request()
File "/usr/lib/python2.5/BaseHTTPServer.py", line 310, in handle_one_request
method()
File "/opt/short_url_redirector/shorturl.py", line 38, in do_GET
self.http_output( http_code, response_txt, long_url )
File "/opt/short_url_redirector/shorturl.py", line 52, in http_output
self.send_response(http_code)
File "/usr/lib/python2.5/BaseHTTPServer.py", line 370, in send_response
self.send_header('Server', self.version_string())
File "/usr/lib/python2.5/BaseHTTPServer.py", line 376, in send_header
self.wfile.write("%s: %s\r\n" % (keyword, value))
File "/usr/lib/python2.5/socket.py", line 274, in write
self.flush()
File "/usr/lib/python2.5/socket.py", line 261, in flush
self._sock.sendall(buffer)
error: (32, 'Broken pipe')
The bulk of these errors seem to stem from having a problem calling the send_header() method where all I'm writing out is this:
self.send_header('Location', long_url)
So I'm curious where in my code to try to trap for this IO exception... do I write try/except calls around each of the self.send_header/self.end_headers/self.wfile.write calls? The other error I see from time to time is this one, but not sure which exception to watch to even catch this:
Traceback (most recent call last):
File "/usr/lib/python2.5/SocketServer.py", line 222, in handle_request
self.process_request(request, client_address)
File "/usr/lib/python2.5/SocketServer.py", line 241, in process_request
self.finish_request(request, client_address)
File "/usr/lib/python2.5/SocketServer.py", line 254, in finish_request
self.RequestHandlerClass(request, client_address, self)
File "/usr/lib/python2.5/SocketServer.py", line 522, in __init__
self.handle()
File "/usr/lib/python2.5/BaseHTTPServer.py", line 316, in handle
self.handle_one_request()
File "/usr/lib/python2.5/BaseHTTPServer.py", line 299, in handle_one_request
self.raw_requestline = self.rfile.readline()
File "/usr/lib/python2.5/socket.py", line 381, in readline
data = self._sock.recv(self._rbufsize)
error: (104, 'Connection reset by peer')

This appears to be a bug in SocketServer, see this link Python Bug: 14574
A fix (works for me in Python 2.7) is to override the SocketServer.StreamRequestHandler finish() method, something like this:
...
def finish(self,*args,**kw):
try:
if not self.wfile.closed:
self.wfile.flush()
self.wfile.close()
except socket.error:
pass
self.rfile.close()
#Don't call the base class finish() method as it does the above
#return SocketServer.StreamRequestHandler.finish(self)

The "broken pipe" exception means that your code tried to write to a socket/pipe which the other end has closed. If the other end is a web browser, the user could have stopped the request. You can ignore the traceback; it does not indicate a serious problem. If you want to suppress the message, you can put a try ... except block around all of the code in your http_output function, and log the exception if you like.
Additionally, if you want your HTTP server to process more than one request at a time, you need your server class to use one of the SocketServer.ForkingMixIn and SocketServer.ThreadingMixIn classes. Check the documentation of the SocketServer module for details.
Add: The "connection reset by peer" exception means that your code tried to read from a dead socket. If you want to suppress the traceback, you will need to extend the BaseHTTPServer class and override the handle_one_request method to add a try ... except block. You will need a new server class anyway, to implement the earlier suggestion about processing more than one request at a time.

In my application, the error didn't occur in finish(), it occurred in handle(). This fix catches the broken pipe errors:
class MyHTTPRequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
...
def handle(self):
try:
BaseHTTPServer.BaseHTTPRequestHandler.handle(self)
except socket.error:
pass

Twisted and starpy error (python)

I'm using this:
from twisted.web.client import getPage
df = getPage(url) # there is some url
I'm getting the following error. Please can anyone guide me on this
ERROR:twsited:Unhandled error in Deferred:
ERROR:twsited:Unhandled Error
Traceback (most recent call last):
File "/usr/local/lib/python2.6/dist-packages/starpy/manager.py", line 123, in lineReceived
self.dispatchIncoming() # does dispatch and clears cache
File "/usr/local/lib/python2.6/dist-packages/starpy/manager.py", line 200, in dispatchIncoming
callback( message )
File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 243, in callback
self._startRunCallbacks(result)
File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 312, in _startRunCallbacks
self._runCallbacks()
--- <exception caught here> ---
File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 328, in _runCallbacks
self.result = callback(self.result, *args, **kw)
File "/usr/local/lib/python2.6/dist-packages/starpy/manager.py", line 298, in errorUnlessResponse
raise error.AMICommandFailure( message )
starpy.error.AMICommandFailure: {'message': 'Channel not specified', 'response': 'Error', 'actionid': 'askme-158811948-5'}
I'm not sure this error is due to getPage() method because even when i've commented this it still give me the same error. Can anyone help. I can't figure out the reason for the error and where it is generated

The code posted is not complete. The error is not due to getPage.
From the stack trace clues, this uses AMIProtocol (line receiver) .
I guess some where you have to specify your protocol channel in AMIProtocol
setVar(self, channel, variable, value) in star.py.
This is not a twisted issue.