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https://issues.apache.org/jira/browse/YARN-99?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13594210#comment-13594210
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omkar vinit joshi commented on YARN-99:
---------------------------------------
The problem of large number of files (no. exceeding max file limit per
directory) may occur at below (* marked) locations and it needs to be fixed at
both the places. The directory structure shown is per local directory.
[For-any-local-dir]
---- [filecache *]
---- [usercache]
[userid]
---- [filecache *]
---- [appcache]
---- [appid]
---- [filecache]
In application specific filecache it is highly improbable that we might hit
that limit whereas in the other two places it is highly likely.
Proposed solution: - Adding an internal parameter (not making it externally
configurable) to “localResourcesTrackerImpl” to control the hierarchical
behavior for different type of resources.
For hierarchical resources; managing hierarchy as follows
<orig-dir> = “path ending with –filecache- “
<orig-dir>
---- (8192 / 8k localized files)
---- 26 directories (a-z) ( Created only if the directory limit is
reached.)
----- [a]
---- (8192 / 8k localized files)
---- 26 directories (a-z)
.
.
.
.
Reason for creating directories with single character;
1) For windows we also have maxpath limit (~255 characters)
2) With this hierarchy we can accommodate >1M files with 3 levels; which is
practically sufficient.
Let me know if I need to look at any specific scenario / corner case / need to
modify the design.
> Jobs fail during resource localization when directories in file cache reaches
> to unix directory limit
> -----------------------------------------------------------------------------------------------------
>
> Key: YARN-99
> URL: https://issues.apache.org/jira/browse/YARN-99
> Project: Hadoop YARN
> Issue Type: Bug
> Components: nodemanager
> Affects Versions: 3.0.0, 2.0.0-alpha
> Reporter: Devaraj K
> Assignee: Devaraj K
>
> If we have multiple jobs which uses distributed cache with small size of
> files, the directory limit reaches before reaching the cache size and fails
> to create any directories in file cache. The jobs start failing with the
> below exception.
> {code:xml}
> java.io.IOException: mkdir of
> /tmp/nm-local-dir/usercache/root/filecache/1701886847734194975 failed
> at org.apache.hadoop.fs.FileSystem.primitiveMkdir(FileSystem.java:909)
> at
> org.apache.hadoop.fs.DelegateToFileSystem.mkdir(DelegateToFileSystem.java:143)
> at org.apache.hadoop.fs.FilterFs.mkdir(FilterFs.java:189)
> at org.apache.hadoop.fs.FileContext$4.next(FileContext.java:706)
> at org.apache.hadoop.fs.FileContext$4.next(FileContext.java:703)
> at
> org.apache.hadoop.fs.FileContext$FSLinkResolver.resolve(FileContext.java:2325)
> at org.apache.hadoop.fs.FileContext.mkdir(FileContext.java:703)
> at org.apache.hadoop.yarn.util.FSDownload.call(FSDownload.java:147)
> at org.apache.hadoop.yarn.util.FSDownload.call(FSDownload.java:49)
> at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
> at java.util.concurrent.FutureTask.run(FutureTask.java:138)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
> at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
> at java.util.concurrent.FutureTask.run(FutureTask.java:138)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)
> {code}
> We should have a mechanism to clean the cache files if it crosses specified
> number of directories like cache size.
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