Rushabh Shah created HDFS-17299:
-----------------------------------
Summary: 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
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
{code:java}
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
createBlockOutputStreamjava.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_1409467162023-12-16
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
createBlockOutputStreamjava.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_1409467642023-12-16
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
createBlockOutputStreamjava.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_1409467962023-12-16
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
createBlockOutputStreamjava.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
Exceptionjava.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...
{code}
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-dev-unsubscr...@hadoop.apache.org
For additional commands, e-mail: hdfs-dev-h...@hadoop.apache.org
