[erlang-bugs] httpc:request_cancel oddities

Chris King <>
Thu Sep 5 04:39:42 CEST 2013

Furthermore, there's a race condition in the cancel_request handler here:

     case ets:lookup(HandlerDb, RequestId) of
     [{_, Pid, _}] ->
         httpc_handler:cancel(RequestId, Pid, From),
          State#state{cancel =
                      [{RequestId, Pid, From} | State#state.cancel]}}

After the ets:lookup, thread death & reuse races with  
httpc_handler:cancel.  The handler thread then dies when it receives a  
cancel message for an unknown request.  Easiest (and probably most  
correct) solution is for the handler thread to ignore cancel messages for  
unknown requests, rather than dying with function_clause as it currently  

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