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  1. Apache NiFi
  2. NIFI-6996

ConsumeWindowsEventLog leads to a stackoverflow when subscription fails

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Details

    • Bug
    • Status: Resolved
    • Major
    • Resolution: Fixed
    • 1.10.0
    • 1.11.0
    • Extensions
    • None

    Description

       

      The ConsumeWindowsEvenLog processor causes a stack overflow when it fails to subscribe to a log.
      Sadly I cannot provide logs (working under an NDA).

      Since I cannot provide logs I will try to describe the flow:
      1. isSubscribed function is called and the subscription fails (line 242)
      2. isSubscribed calls unsubscribe function (line 250)
      3. unsubscribe function calls isSubscribed (line 290)
      4. repeat

       

      The second line causes the issue:

       

      private boolean isSubscribed() {
          final boolean subscribed = subscriptionHandle != null && subscriptionHandle.getPointer() != null;
          final boolean subscriptionFailed = evtSubscribeCallback != null
              && ((EventSubscribeXmlRenderingCallback) evtSubscribeCallback).isSubscriptionFailed();
          final boolean subscribing = subscribed && !subscriptionFailed;
          getLogger().debug("subscribing? {}, subscribed={}, subscriptionFailed={}", new Object[]{subscribing, subscribed, subscriptionFailed});
          if (subscriptionFailed) {
              getLogger().info("Canceling a failed subscription.");
              unsubscribe();
          }
          return subscribing;
      }

      If evtSubscribeCallback is null we're stuck in a stackoverflow, the isSubscriptionFailed function in EventSubscribeXmlRenderingCallback returns a boolean called subscriptionFailed which is private and set to true when it fails to subscribe, nowhere in the class is it set back to false.

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