[HDFS-13898] Throw retriable exception for getBlockLocations when ObserverNameNode is in safemode

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: HDFS-12943, 3.3.0
• Hadoop Flags: Reviewed
• Assignee: Chao Sun
• Reporter: Chao Sun
• Created: 06/Sep/18 06:28
• Updated: 13/Aug/19 17:10
• Resolved: 21/Sep/18 22:14

Description

When ObserverNameNode is in safe mode, getBlockLocations may throw safe mode exception if the given file doesn't have any block yet. 

    try {
      checkOperation(OperationCategory.READ);
      res = FSDirStatAndListingOp.getBlockLocations(
          dir, pc, srcArg, offset, length, true);
      if (isInSafeMode()) {
        for (LocatedBlock b : res.blocks.getLocatedBlocks()) {
          // if safemode & no block locations yet then throw safemodeException
          if ((b.getLocations() == null) || (b.getLocations().length == 0)) {
            SafeModeException se = newSafemodeException(
                "Zero blocklocations for " + srcArg);
            if (haEnabled && haContext != null &&
                haContext.getState().getServiceState() == HAServiceState.ACTIVE) {
              throw new RetriableException(se);
            } else {
              throw se;
            }
          }
        }
      }

It only throws RetriableException for active NN so requests on observer may just fail.

Issue Links

• relates to: HDFS-14723 Add helper method FSNamesystem#setBlockManagerForTesting() in branch-2