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Xiaoqiao He commented on HDFS-17299: ------------------------------------ Connection meet some issues? Seems we both have this same opinion. But I don't have idea to fix it smooth. Because at NameNode side it doesn't recognise the dead node/racks in time, at Client side it doesn't know how many racks in the cluster. Any ideas? > HDFS is not rack failure tolerant while creating a new file. > ------------------------------------------------------------ > > Key: HDFS-17299 > URL: https://issues.apache.org/jira/browse/HDFS-17299 > Project: Hadoop HDFS > Issue Type: Bug > Affects Versions: 2.10.1 > Reporter: Rushabh Shah > Priority: Critical > Attachments: repro.patch > > > Recently we saw an HBase cluster outage when we mistakenly brought down 1 AZ. > Our configuration: > 1. We use 3 Availability Zones (AZs) for fault tolerance. > 2. We use BlockPlacementPolicyRackFaultTolerant as the block placement policy. > 3. We use the following configuration parameters: > dfs.namenode.heartbeat.recheck-interval: 600000 > dfs.heartbeat.interval: 3 > So it will take 1230000 ms (20.5mins) to detect that datanode is dead. > > Steps to reproduce: > # Bring down 1 AZ. > # HBase (HDFS client) tries to create a file (WAL file) and then calls > hflush on the newly created file. > # DataStreamer is not able to find blocks locations that satisfies the rack > placement policy (one copy in each rack which essentially means one copy in > each AZ) > # Since all the datanodes in that AZ are down but still alive to namenode, > the client gets different datanodes but still all of them are in the same AZ. > See logs below. > # HBase is not able to create a WAL file and it aborts the region server. > > Relevant logs from hdfs client and namenode > > {noformat} > 2023-12-16 17:17:43,818 INFO [on default port 9000] FSNamesystem.audit - > allowed=true ugi=hbase/<rs-name> (auth:KERBEROS) ip=<rs-IP> > cmd=create src=/hbase/WALs/<WAL-file> dst=null > 2023-12-16 17:17:43,978 INFO [on default port 9000] hdfs.StateChange - > BLOCK* allocate blk_1214652565_140946716, replicas=<AZ-1-dn-1>:50010, > <AZ-2-dn-1>:50010, <AZ-3-dn-1>:50010 for /hbase/WALs/<WAL-file> > 2023-12-16 17:17:44,061 INFO [Thread-39087] hdfs.DataStreamer - Exception in > createBlockOutputStream > java.io.IOException: Got error, status=ERROR, status message , ack with > firstBadLink as <AZ-2-dn-1>:50010 > at > org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil.checkBlockOpStatus(DataTransferProtoUtil.java:113) > at > org.apache.hadoop.hdfs.DataStreamer.createBlockOutputStream(DataStreamer.java:1747) > at > org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1651) > at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:715) > 2023-12-16 17:17:44,061 WARN [Thread-39087] hdfs.DataStreamer - Abandoning > BP-179318874-<NN-IP>-1594838129323:blk_1214652565_140946716 > 2023-12-16 17:17:44,179 WARN [Thread-39087] hdfs.DataStreamer - Excluding > datanode > DatanodeInfoWithStorage[<AZ-2-dn-1>:50010,DS-a493abdb-3ac3-49b1-9bfb-848baf5c1c2c,DISK] > 2023-12-16 17:17:44,339 INFO [on default port 9000] hdfs.StateChange - > BLOCK* allocate blk_1214652580_140946764, replicas=<AZ-1-dn-2>:50010, > <AZ-3-dn-2>:50010, <AZ-2-dn-2>:50010 for /hbase/WALs/<WAL-file> > 2023-12-16 17:17:44,369 INFO [Thread-39087] hdfs.DataStreamer - Exception in > createBlockOutputStream > java.io.IOException: Got error, status=ERROR, status message , ack with > firstBadLink as <AZ-2-dn-2>:50010 > at > org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil.checkBlockOpStatus(DataTransferProtoUtil.java:113) > at > org.apache.hadoop.hdfs.DataStreamer.createBlockOutputStream(DataStreamer.java:1747) > at > org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1651) > at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:715) > 2023-12-16 17:17:44,369 WARN [Thread-39087] hdfs.DataStreamer - Abandoning > BP-179318874-NN-IP-1594838129323:blk_1214652580_140946764 > 2023-12-16 17:17:44,454 WARN [Thread-39087] hdfs.DataStreamer - Excluding > datanode > DatanodeInfoWithStorage[AZ-2-dn-2:50010,DS-46bb45cc-af89-46f3-9f9d-24e4fdc35b6d,DISK] > 2023-12-16 17:17:44,522 INFO [on default port 9000] hdfs.StateChange - > BLOCK* allocate blk_1214652594_140946796, replicas=<AZ-1-dn-2>:50010, > <AZ-2-dn-3>:50010, <AZ-3-dn-3>:50010 for /hbase/WALs/<WAL-file> > 2023-12-16 17:17:44,712 INFO [Thread-39087] hdfs.DataStreamer - Exception in > createBlockOutputStream > java.io.IOException: Got error, status=ERROR, status message , ack with > firstBadLink as <AZ-2-dn-3>:50010 > at > org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil.checkBlockOpStatus(DataTransferProtoUtil.java:113) > at > org.apache.hadoop.hdfs.DataStreamer.createBlockOutputStream(DataStreamer.java:1747) > at > org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1651) > at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:715) > 2023-12-16 17:17:44,712 WARN [Thread-39087] hdfs.DataStreamer - Abandoning > BP-179318874-NN-IP-1594838129323:blk_1214652594_140946796 > 2023-12-16 17:17:44,732 WARN [Thread-39087] hdfs.DataStreamer - Excluding > datanode > DatanodeInfoWithStorage[<AZ-2-dn-3>:50010,DS-86b77463-a26f-4f42-ae1b-21b75c407203,DISK] > 2023-12-16 17:17:44,855 INFO [on default port 9000] hdfs.StateChange - > BLOCK* allocate blk_1214652607_140946850, replicas=<AZ-1-dn-4>:50010, > <AZ-2-dn-4>:50010, <AZ-3-dn-4>:50010 for /hbase/WALs/<WAL-file> > 2023-12-16 17:17:44,867 INFO [Thread-39087] hdfs.DataStreamer - Exception in > createBlockOutputStream > java.io.IOException: Got error, status=ERROR, status message , ack with > firstBadLink as <AZ-2-dn-4>:50010 > at > org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil.checkBlockOpStatus(DataTransferProtoUtil.java:113) > at > org.apache.hadoop.hdfs.DataStreamer.createBlockOutputStream(DataStreamer.java:1747) > at > org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1651) > at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:715) > 2023-12-16 17:17:44,988 WARN [Thread-39087] hdfs.DataStreamer - DataStreamer > Exception > java.io.IOException: Unable to create new block. > at > org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1665) > at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:715) > 2023-12-16 17:17:44,988 WARN [Thread-39087] hdfs.DataStreamer - Could not > get block locations. Source file "/hbase/WALs/<WAL-file>" - Aborting... > {noformat} > > *Proposed fix:* > Client always correctly identifies the bad datanode in the pipeline. > The number of retries dfs client makes is controlled by > dfs.client.block.write.retries (defaults to 3). So in total it tries 4 times > to create the pipeline. > So on the 3rd or 4th attempt, if we see all the excluded nodes in the > pipeline belongs to the same rack, we can pass the hint to namenode to > exclude that rack for the next block. > Once that rack is back online, Replication monitor will handle to replicate > that block to that rack. > -- This message was sent by Atlassian Jira (v8.20.10#820010) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org