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https://issues.apache.org/jira/browse/YARN-6929?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16810986#comment-16810986
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Eric Yang commented on YARN-6929:
---------------------------------
If I understand the patch correctly, ${clusterTsDir}/${bucketDir}/${appId} is
the proposed path format to store app logs. This is only improved slightly in
the number of application logs that can be hold, and difficult to guess the
location of the application log. clusterTsDir will stay static until the next
resource manager restart. Most logs will stay in one clusterTsDir's bucketDir
subdirectories. User needs to calculate bucketDir from appId.getId() /
maxBucket (1048576). According to ext4, maximum subdirectories in a directory
is 64000, which is less than default bucket size. I think this solution
doesn't scale well because it will try to fill up bucket id 1 to 1048576 jobs
then move on to next. If we create one job every second, it will take roughly
12 days to fill up the first bucket. Fetching 1048576 inode info might be
expensive operation.
If we are worry about scaling number of app directory in one subdirectory.
Partition algorithm can be used by splitting every 4 digits of the application
id. For example, application_1554419602336_0001 will create subdirectory
0001/2336/application_1554419602336_0001 base on 2 parts of the less
significant bits. This will scale log size location to 99,980,001. For clean
up, walk the directories and find last modified time exceeding the log
retention period. This can help to balance the memory usage in for-loop to get
subdirectories size of 9999 instead of 1048576. Which is more manageable and
take less time for gc to clean up.
> yarn.nodemanager.remote-app-log-dir structure is not scalable
> -------------------------------------------------------------
>
> Key: YARN-6929
> URL: https://issues.apache.org/jira/browse/YARN-6929
> Project: Hadoop YARN
> Issue Type: Bug
> Components: log-aggregation
> Affects Versions: 2.7.3
> Reporter: Prabhu Joseph
> Assignee: Prabhu Joseph
> Priority: Major
> Attachments: YARN-6929.1.patch, YARN-6929.2.patch, YARN-6929.2.patch,
> YARN-6929.3.patch, YARN-6929.4.patch, YARN-6929.5.patch, YARN-6929.6.patch,
> YARN-6929.patch
>
>
> The current directory structure for yarn.nodemanager.remote-app-log-dir is
> not scalable. Maximum Subdirectory limit by default is 1048576 (HDFS-6102).
> With retention yarn.log-aggregation.retain-seconds of 7days, there are more
> chances LogAggregationService fails to create a new directory with
> FSLimitException$MaxDirectoryItemsExceededException.
> The current structure is
> <yarn.nodemanager.remote-app-log-dir>/<user>/logs/<job_name>. This can be
> improved with adding date as a subdirectory like
> <yarn.nodemanager.remote-app-log-dir>/<user>/logs/<date>/<job_name>
> {code}
> WARN
> org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService:
> Application failed to init aggregation
> org.apache.hadoop.yarn.exceptions.YarnRuntimeException:
> org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.FSLimitException$MaxDirectoryItemsExceededException):
> The directory item limit of /app-logs/yarn/logs is exceeded: limit=1048576
> items=1048576
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.verifyMaxDirItems(FSDirectory.java:2021)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.addChild(FSDirectory.java:2072)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.unprotectedMkdir(FSDirectory.java:1841)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsRecursively(FSNamesystem.java:4351)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInternal(FSNamesystem.java:4262)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInt(FSNamesystem.java:4221)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:4194)
>
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:813)
>
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.mkdirs(ClientNamenodeProtocolServerSideTranslatorPB.java:600)
>
> at
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
>
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:619)
>
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:962)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2039)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2035)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:415)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
>
> at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2033)
> at
> org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService.createAppDir(LogAggregationService.java:308)
>
> at
> org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService.initAppAggregator(LogAggregationService.java:366)
>
> at
> org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService.initApp(LogAggregationService.java:320)
>
> at
> org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService.handle(LogAggregationService.java:443)
>
> at
> org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService.handle(LogAggregationService.java:67)
>
> at
> org.apache.hadoop.yarn.event.AsyncDispatcher.dispatch(AsyncDispatcher.java:173)
>
> at
> org.apache.hadoop.yarn.event.AsyncDispatcher$1.run(AsyncDispatcher.java:106)
> at java.lang.Thread.run(Thread.java:745)
> Caused by:
> org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.FSLimitException$MaxDirectoryItemsExceededException):
> The directory item limit of /app-logs/yarn/logs is exceeded: limit=1048576
> items=1048576
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.verifyMaxDirItems(FSDirectory.java:2021)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.addChild(FSDirectory.java:2072)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.unprotectedMkdir(FSDirectory.java:1841)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsRecursively(FSNamesystem.java:4351)
>
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInternal(FSNamesystem.java:4262)
>
> {code}
> Thanks to Robert Mancuso for finding this issue.
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