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  1. EJB Client Library (AS7+)
  2. EJBCLIENT-24

Missing weak affinity for clustered stateful session bean can lead to invocation ending up on a non-optimal node

    Details

    • Type: Bug
    • Status: Resolved (View Workflow)
    • Priority: Major
    • Resolution: Done
    • Affects Version/s: 1.0.1.Final
    • Fix Version/s: 1.0.2.Final
    • Labels:
      None

      Description

      From a mail discussion:

      > On 2/11/12 8:55 AM, Jaikiran Pai wrote:
      >> Reviving this old discussion again, now in the context of
      >> https://issues.jboss.org/browse/AS7-3716. The issue there is still under
      >> investigation so I'm not 100% sure about the problem, but I do have a
      >> theory that it might very well be related to our affinity logic.
      >>
      >> So like we discussed earlier in this mail and like David explained, the
      >> weak affinity (along with the hard affinity) is there to make sure that
      >> we always (whenever possible) direct the client invocations to the node
      >> which owns the session. Our current implementation I believe is missing
      >> a piece which is not letting this happen. To recap, how we deal with
      >> affinities, consider a server on which we have a SFSB deployed which
      >> belongs to cluster "foo" consisting node A and B:
      >>
      >> 1) Client looks up SFSB which triggers a session creation on node A. The
      >> server (node A) responds back with a session id and also sends along a
      >> "hard affinity" == "foo cluster".
      >> 2) Client invokes on the proxy which then trigger the receiver selection
      >> logic where we find that the locator is associated with a hard affinity
      >> == foo cluster.
      >> 3) We then look for a receiver which belongs to "foo cluster" within the
      >> current EJB client context. Now at this step, there's no guarantee that
      >> the client context will return node A receiver. It might very well
      >> return node B receiver too. Ideally we do want node A receiver, since
      >> that's what owns the session.
      >>
      >> Our initial idea while implementing the EJB protocol was to pass back
      >> the weak affinity only during method invocations. i.e. whenever the
      >> client invokes on the proxy, along with the method invocation result we
      >> would also get a weak affinity (which points to the node which owns the
      >> session). So subsequent requests (starting the second one) on the
      >> proxy would result in the invocation being directed correctly to node A.
      >>
      >> I believe we should also send back a weak affinity (along with the
      >> current hard affinity) on the session creation response too. That'll
      >> make sure that even the first invocation on the SFSB proxy will take
      >> into account the node which owns the session. I'll be implementing this
      >> now and running some tests. Just wanted to give you guys a heads up and
      >> make sure I we agree on this change.

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                • Assignee:
                  jaikiran Jaikiran Pai
                  Reporter:
                  jaikiran Jaikiran Pai
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                  • Created:
                    Updated:
                    Resolved: