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Jitendra Nath Pandey commented on HDFS-11030: --------------------------------------------- +1. Thanks for the patch [~liuml07] > TestDataNodeVolumeFailure#testVolumeFailure is flaky (though passing) > --------------------------------------------------------------------- > > Key: HDFS-11030 > URL: https://issues.apache.org/jira/browse/HDFS-11030 > Project: Hadoop HDFS > Issue Type: Sub-task > Components: datanode, test > Affects Versions: 2.7.0 > Reporter: Mingliang Liu > Assignee: Mingliang Liu > Attachments: HDFS-11030-branch-2.000.patch, HDFS-11030.000.patch > > > TestDataNodeVolumeFailure#testVolumeFailure fails a volume and verifies the > blocks and files are replicated correctly. > # To fail a volume, it deletes all the blocks and sets the data dir read only. > {code:title=testVolumeFailure() snippet} > // fail the volume > // delete/make non-writable one of the directories (failed volume) > data_fail = new File(dataDir, "data3"); > failedDir = MiniDFSCluster.getFinalizedDir(dataDir, > cluster.getNamesystem().getBlockPoolId()); > if (failedDir.exists() && > //!FileUtil.fullyDelete(failedDir) > !deteteBlocks(failedDir) > ) { > throw new IOException("Could not delete hdfs directory '" + failedDir + > "'"); > } > data_fail.setReadOnly(); > failedDir.setReadOnly(); > {code} > However, there are two bugs here, which make the blocks not deleted. > #- The {{failedDir}} directory for finalized blocks is not calculated > correctly. It should use {{data_fail}} instead of {{dataDir}} as the base > directory. > #- When deleting block files in {{deteteBlocks(failedDir)}}, it assumes that > there is no subdirectories in the data dir. This assumption was also noted in > the comments. > {quote} > // we use only small number of blocks to avoid creating subdirs in the > data dir.. > {quote} > This is not true. On my local cluster and MiniDFSCluster, there will be > subdir0/subdir0/ two level directories regardless of the number of blocks. > # Meanwhile, to fail a volume, it also needs to trigger the DataNode removing > the volume and send block report to NN. This is basically in the > {{triggerFailure()}} method. > {code} > private void triggerFailure(String path, long size) throws IOException { > NamenodeProtocols nn = cluster.getNameNodeRpc(); > List<LocatedBlock> locatedBlocks = > nn.getBlockLocations(path, 0, size).getLocatedBlocks(); > > for (LocatedBlock lb : locatedBlocks) { > DatanodeInfo dinfo = lb.getLocations()[1]; > ExtendedBlock b = lb.getBlock(); > try { > accessBlock(dinfo, lb); > } catch (IOException e) { > System.out.println("Failure triggered, on block: " + b.getBlockId() + > > "; corresponding volume should be removed by now"); > break; > } > } > } > {code} > Accessing those blocks will not trigger failures if the directory is > read-only (while the block files are all there). I ran the tests multiple > times without triggering this failure. We have to write new block files to > the data directories, or we should have deleted the blocks correctly. I think > we need to add some assertion code after triggering the volume failure. The > assertions should check the datanode volume failure summary explicitly to > make sure a volume failure is triggered (and noticed). > # To make sure the NameNode be aware of the volume failure, the code > explictily send block reports to NN. > {code:title=TestDataNodeVolumeFailure#testVolumeFailure()} > cluster.getNameNodeRpc().blockReport(dnR, bpid, reports, > new BlockReportContext(1, 0, System.nanoTime(), 0, false)); > {code} > Generating block report code is complex, which is actually the internal logic > of {{BPServiceActor}}. We may have to update this code it changes. In fact, > the volume failure is now sent by DataNode via heartbeats. We should trigger > a heartbeat request here; and make sure the NameNode handles the heartbeat > before we verify the block states. > # When verifying via {{verify()}}, it counts the real block files and assert > that real block files plus underreplicated blocks should cover all blocks. > Before counting underreplicated blocks, it triggered the {{BlockManager}} to > compute the datanode work: > {code} > // force update of all the metric counts by calling computeDatanodeWork > BlockManagerTestUtil.getComputedDatanodeWork(fsn.getBlockManager()); > {code} > However, counting physical block files and underreplicated blocks are not > atomic. The NameNode will inform of the DataNode the computed work at next > heartbeat. So I think this part of code may fail when some blocks are > replicated and the number of physical block files is made stale. To avoid > this case, I think we should keep the DataNode from sending the heartbeat > after that. A simple solution is to set {{dfs.heartbeat.interval}} long > enough. > This unit test has been there for years and it seldom fails, just because > it's never triggered a real volume failure. -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org