intermittent crashes in HttpSM::state_http_server_open()

[John Rushford]

We're running ats 6.2.2 and recently we've seen  a rash of crashes in
HttpSM::state_http_server_open() due to the handler receiving an unexpected
event, VC_EVENT_WRITE_COMPLETE, the handler calls ink_release_assert() in
this case.
The coredumps all show an http POST request to an origin server was in
progress.  These events and coredumps are intermittent and I'm unable to
reproduce the issue in our test environment.  I was wondering if anyone has
seen this before and has an idea why the event occurs.

In the meantime, I have patched this build so that any unexpected events in
this handler send a connection error instead of calling
ink_release_assert().  Here is my patch and would like to know if this
should be pushed upstream to master.

ATS 6.2.x code:

  1 @@ -1759,6 +1759,8 @@ HttpSM::state_http_server_open(int event, void
*data)
  2         do_http_server_open();
  3       }
  4       break;
  5  +  default:
  6  +    Error("[HttpSM::state_http_server_open] Unknown event: %d",
event);
  7     case VC_EVENT_ERROR:
  8     case NET_EVENT_OPEN_FAILED:
  9       t_state.current.state = HttpTransact::CONNECTION_ERROR;
 10  @@ -1793,11 +1795,6 @@ HttpSM::state_http_server_open(int event, void
*data    )
 11       t_state.current.state =
HttpTransact::CONGEST_CONTROL_CONGESTED_ON_M;
 12       call_transact_and_set_next_state(HttpTransact::HandleResponse);
 13       return 0;
 14  -
 15  -  default:
 16  -    Error("[HttpSM::state_http_server_open] Unknown event: %d",
event);
 17  -    ink_release_assert(0);
 18  -    return 0;
 19     }
 20
 21     return 0;