3 Replies Latest reply: Dec 10, 2012 2:10 PM by Joe Weinstein-Oracle RSS

    Hung queries, and Oracle thin driver query timeout implementation

      We are seeing occasional instances of stuck threads, where the code is in Oracle thin XA driver code waiting for a socket read for a response from the database. Usually only one thread at a time. The connection never terminates and we have to shut down WebLogic to clear it. The DBAs tell us that all connections to the 11g RAC cluster members from our hosts are idle, with no hung or long-running transactions.

      This happens every few days across two WebLogic 10.3.5 clustered instances in our QA environment, usually not the same time on two servers (one had four incidents, the other had only one, in the last 15 or so days). Sometimes it has resulted in a hung server, as the driver is holding a lock that blocks other threads (today we had numerous threads block in a TX rollback).

      I'm guessing our WebLogic instance somehow is not getting the connection close from the remote host. BTW, there is no firewall between us and the DB. I have not got any strong suspect for the cause (although we are running Linux on a VMWare 4.0 VM, which always worries me).

      Ordinarily I'd either ask the application to set a query timeout, or set the query timeout parameter for the connection pools as a workaround (we are using a MultiDatasource), so the transaction would at least abort and the application can handle it. However, while the Oracle driver does support java.sql.Statement.setQueryTimeout(), some brief investigation on my part leads me to believe the timeout is implemented on the server side and not the client side - so that if it is indeed the case that WebLogic does not see the close on the connection, it also would never see the timeout.

      Two questions:
      1. Is my suspicion about server-side implementation of timeout for Oracle 11g correct?
      2. If so, is there some property I can set for the driver that will implement a socket timeout? Is this "safe"?

      Thanks for any help!

      [ Oracle WebLogic 10.3.5, HotSpot 64 bit JVM 1.6.0_29 on RHEL 5.6 on VMWare; Oracle Thin XA driver bundled with WebLogic; Oracle RAC 11g (three-node cluster)]

      Edited by: SteveElkind on Dec 3, 2012 5:25 AM