[IMPALA-7598] Planner timeline not set in the runtime profile incase of errors

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: Impala 3.1.0
• Component/s: Frontend
• Labels: newbie ramp-up
• Epic Color: ghx-label-5
• Assignee: Unassigned
• Reporter: Bharath Vissapragada
• Created: 19/Sep/18 23:41
• Updated: 19/Jun/20 19:25

Description

Currently, the frontend sets the "Query compilation" timeline only if doCreateExecRequest() finishes successfully.

private TExecRequest doCreateExecRequest(TQueryCtx queryCtx...) {
  ...... <snip>......
  timeline.markEvent("Planning finished");
  result.setTimeline(timeline.toThrift());
  return result;
}

There can be cases where the timeline could be useful for debugging when the planning fails.

One recent case I came across is the exhaustion of retries on InconsistentMetadataFetchException. For every retry of query due to this exception, we add a timeline event.

 while (true) {
      try {
        return doCreateExecRequest(queryCtx, timeline, explainString);
      } catch (InconsistentMetadataFetchException e) {
        if (attempt++ == INCONSISTENT_METADATA_NUM_RETRIES) {
          throw e;
        }
        if (attempt > 1) {
          // Back-off a bit on later retries.
          Uninterruptibles.sleepUninterruptibly(200 * attempt, TimeUnit.MILLISECONDS);
        }
        timeline.markEvent(
            String.format("Retrying query planning due to inconsistent metadata "
                    + "fetch, attempt %s of %s: ",
                attempt, INCONSISTENT_METADATA_NUM_RETRIES)
            + e.getMessage());

However, if the planning eventually fails, the timeline about retries is gone. This would've confirmed that the query was re-tried for 10 times.

Would be really useful if we can populate the partial timeline, even if the planning failed.