[HDFS-13863] FsDatasetImpl should log DiskOutOfSpaceException

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1.0, 2.9.1, 3.0.3
• Fix Version/s: 3.2.0, 3.0.4, 3.1.2
• Component/s: hdfs
• Hadoop Flags: Reviewed
• Assignee: Hui Fei
• Reporter: Hui Fei
• Created: 24/Aug/18 11:33
• Updated: 02/Oct/19 17:14
• Resolved: 30/Aug/18 03:27

Description

The code in function createRbw as follow

        try {
          // First try to place the block on a transient volume.
          ref = volumes.getNextTransientVolume(b.getNumBytes());
          datanode.getMetrics().incrRamDiskBlocksWrite();
        } catch (DiskOutOfSpaceException de) {
          // Ignore the exception since we just fall back to persistent storage.
        } finally {
          if (ref == null) {
            cacheManager.release(b.getNumBytes());
          }
        }

I think we should log the exception because it took me long time to resolve problems, and maybe others face the same problems.
When i test ram_disk, i found no data was written into randomdisk. I debug, deep into the source code, and found that randomdisk size was less than reserved space. I think if message was logged, i would resolve the problem quickly.