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  1. IMPALA
  2. IMPALA-5576

Wrong Cancel() in QueryState::ReportExecStatusAux() can lead to coordinator hang

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: Impala 2.9.0
    • Fix Version/s: Impala 2.10.0
    • Component/s: Distributed Exec
    • Labels:

      Description

      Code introduced as part of IMPALA-2550 makes a hang possible if the report exec function fails to get a backend client. The new code cancels the local fragments but the status will never be reported to the coordinator, so it will wait indefinitely for their reports.

      void QueryState::ReportExecStatusAux(bool done, const Status& status,
          FragmentInstanceState* fis, bool instances_started) {
        // if we're reporting an error, we're done
        DCHECK(status.ok() || done);
        // if this is not for a specific fragment instance, we're reporting an error
        DCHECK(fis != nullptr || !status.ok());
        DCHECK(fis == nullptr || fis->IsPrepared());
      
        // This will send a report even if we are cancelled.  If the query completed correctly
        // but fragments still need to be cancelled (e.g. limit reached), the coordinator will
        // be waiting for a final report and profile.
      
        Status coord_status;
        ImpalaBackendConnection coord(ExecEnv::GetInstance()->impalad_client_cache(),
            query_ctx().coord_address, &coord_status);
        if (!coord_status.ok()) {
          // TODO: this might flood the log
          LOG(WARNING) << "Couldn't get a client for " << query_ctx().coord_address
              <<"\tReason: " << coord_status.GetDetail();
          if (instances_started) Cancel();
          return;
        }
      

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              • Assignee:
                Unassigned
                Reporter:
                mjacobs Matthew Jacobs
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                • Created:
                  Updated:
                  Resolved: