PH18898: WEBSOCKET CONNECTIONS CLOSING RESULTS IN HUNG THREADS

9.0.5.3: WebSphere Application Server traditional Version 9.0.5 Fix Pack 3

APAR status

• Closed as program error.

Error description

• Threads are being reported as hung in a callstack similar to
  the following:
  
  "WebContainer : 24"
  J9VMThread:0x0000000009917000, j9thread_t:0x00007F428C76C900,
  java/lang/Thread:0x00000006A9144098, state:CW, prio=5
  
  (java/lang/Thread getId:0x365, isDaemon:true)
   (native thread
  ID:0x698B, native priority:0x5, native policy:UNKNOWN,
  vmstate:CW, vm thread flags:0x00000101)
   (native stack address
  range from:0x00007F427E2B8000, to:0x00007F427E2F8000,
  size:0x40000)
   CPU usage total: 26.985705856 secs, current
  category="Application"
  Waiting on:
  com/ibm/ws/wsoc/WsocConnLink$1@0x00000006B4669E10 Owned by:
  <unowned>
   Heap bytes allocated since last GC cycle=0 (0x0)
  
  Java callstack:
   at java/lang/Object.wait(Native Method)
   at
  java/lang/Object.wait(Object.java:172(Compiled Code))
   at com/ib
  m/ws/wsoc/WsocConnLink.finishReadBeforeClose(WsocConnLink.java:8
  14)
   at
  com/ibm/ws/wsoc/SessionImpl.close(SessionImpl.java:394)
   at com/
  ibm/ws/wsoc/EndpointManager.httpSessionExpired(EndpointManager.j
  ava:166)
   at com/ibm/ws/wsoc/WsocHttpSessionListener.sessionDest
  royed(WsocHttpSessionListener.java:63)
   at com/ibm/ws/webcontain
  er/managedobject/ManagedObjectListenerWrapper.sessionDestroyed(M
  anagedObjectListenerWrapper.java:90)
   at com/ibm/ws/session/http
  /HttpSessionObserver.sessionDestroyed(HttpSessionObserver.java:2
  02)
   at com/ibm/ws/session/SessionEventDispatcher.sessionDestroy
  ed(SessionEventDispatcher.java:160)
   at com/ibm/ws/session/Store
  Callback.sessionInvalidated(StoreCallback.java:126(Compiled
  Code))
   at com/ibm/ws/session/store/memory/MemorySession.invalid
  ate(MemorySession.java:226(Compiled Code))
   at com/ibm/ws/sessio
  
  n/store/memory/MemorySession.invalidate(MemorySession.java:894)
  
  at com/ibm/ws/session/store/memory/MemoryStore.checkSessionStill
  Valid(MemoryStore.java:429(Compiled Code))
   at com/ibm/ws/sessio
  n/SessionManager.getSession(SessionManager.java:492(Compiled
  Code))
   at com/ibm/ws/session/SessionManager.getSession(SessionM
  anager.java:475(Compiled Code))
   at com/ibm/ws/session/SessionMa
  nager.getSession(SessionManager.java:706(Compiled Code))
   at com
  /ibm/ws/session/SessionContext.getIHttpSession(SessionContext.ja
  va:490(Compiled Code))
   at com/ibm/ws/session/SessionContext.ses
  sionPreInvoke(SessionContext.java:647(Compiled Code))
   at com/ib
  m/ws/webcontainer/srt/SRTRequestContext.sessionPreInvoke(SRTRequ
  estContext.java:69(Compiled Code))
  
  These threads may block
  other threads. Also, the threads may never come out of this
  state, eventually resulting in exhaustion of the thread pool.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of Websockets on IBM WebSphere    *
  *                  Application Servers                         *
  ****************************************************************
  * PROBLEM DESCRIPTION: Reading a Websocket message on a        *
  *                      connection while also closing the       *
  *                      same connection may hang a thread due   *
  *                      a race condition.                       *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Thread is hung in Websocket code.  Thread was reading data on
  a Websocket connection while another thread was closing the
  same connection.
  

Problem conclusion

• Code was added to fix a race condition.
  
  The fix for this APAR is currently targeted for inclusion in
  fix pack 9.0.5.3 and Liberty 19.0.0.8  Please refer to the
  Recommended
  Updates
  page for delivery information:
  http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  WEBS APP SERV N

• Fixed component ID

  5724H8800

Applicable component levels

• R900 PSY

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