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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9053) Support large directories efficiently using B-Tree
Date Tue, 22 Sep 2015 14:39:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14902728#comment-14902728
] 

Hadoop QA commented on HDFS-9053:
---------------------------------

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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | pre-patch |  19m 50s | Pre-patch trunk compilation is healthy. |
| {color:green}+1{color} | @author |   0m  0s | The patch does not contain any @author tags.
|
| {color:green}+1{color} | tests included |   0m  0s | The patch appears to include 7 new
or modified test files. |
| {color:green}+1{color} | javac |   7m 56s | There were no new javac warning messages. |
| {color:green}+1{color} | javadoc |  10m  7s | There were no new javadoc warning messages.
|
| {color:green}+1{color} | release audit |   0m 25s | The applied patch does not increase
the total number of release audit warnings. |
| {color:green}+1{color} | checkstyle |   2m  4s | There were no new checkstyle issues. |
| {color:red}-1{color} | whitespace |   0m  8s | The patch has 2  line(s) that end in whitespace.
Use git apply --whitespace=fix. |
| {color:green}+1{color} | install |   1m 37s | mvn install still works. |
| {color:green}+1{color} | eclipse:eclipse |   0m 34s | The patch built with eclipse:eclipse.
|
| {color:green}+1{color} | findbugs |   4m 24s | The patch does not introduce any new Findbugs
(version 3.0.0) warnings. |
| {color:green}+1{color} | common tests |  23m  9s | Tests passed in hadoop-common. |
| {color:red}-1{color} | hdfs tests | 159m 26s | Tests failed in hadoop-hdfs. |
| | | 229m 45s | |
\\
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|| Reason || Tests ||
| Failed unit tests | hadoop.cli.TestXAttrCLI |
|   | hadoop.fs.viewfs.TestViewFsWithXAttrs |
|   | hadoop.fs.TestSWebHdfsFileContextMainOperations |
|   | hadoop.cli.TestAclCLI |
|   | hadoop.fs.TestHDFSFileContextMainOperations |
|   | hadoop.tracing.TestTracing |
|   | hadoop.security.TestRefreshUserMappings |
|   | hadoop.security.TestPermissionSymlinks |
|   | hadoop.fs.TestSymlinkHdfsFileContext |
|   | hadoop.fs.TestUrlStreamHandler |
|   | hadoop.fs.viewfs.TestViewFileSystemAtHdfsRoot |
|   | hadoop.fs.viewfs.TestViewFileSystemWithXAttrs |
|   | hadoop.fs.TestSymlinkHdfsFileSystem |
|   | hadoop.tools.TestJMXGet |
|   | hadoop.fs.viewfs.TestViewFsDefaultValue |
|   | hadoop.cli.TestHDFSCLI |
|   | hadoop.security.TestPermission |
|   | hadoop.fs.viewfs.TestViewFsHdfs |
|   | hadoop.cli.TestDeleteCLI |
|   | hadoop.fs.TestFcHdfsCreateMkdir |
|   | hadoop.fs.viewfs.TestViewFsWithAcls |
|   | hadoop.TestGenericRefresh |
|   | hadoop.fs.viewfs.TestViewFsAtHdfsRoot |
|   | hadoop.tracing.TestTracingShortCircuitLocalRead |
|   | hadoop.fs.TestFcHdfsPermission |
|   | hadoop.hdfs.web.TestWebHDFSOAuth2 |
|   | hadoop.tracing.TestTraceAdmin |
|   | hadoop.cli.TestCacheAdminCLI |
|   | hadoop.TestRefreshCallQueue |
|   | hadoop.fs.TestEnhancedByteBufferAccess |
|   | hadoop.cli.TestCryptoAdminCLI |
|   | hadoop.fs.viewfs.TestViewFileSystemHdfs |
|   | hadoop.fs.viewfs.TestViewFileSystemWithAcls |
|   | hadoop.fs.TestFcHdfsSetUMask |
|   | hadoop.fs.viewfs.TestViewFsFileStatusHdfs |
|   | hadoop.fs.shell.TestHdfsTextCommand |
| Timed out tests | org.apache.hadoop.fs.contract.hdfs.TestHDFSContractDelete |
\\
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|| Subsystem || Report/Notes ||
| Patch URL | http://issues.apache.org/jira/secure/attachment/12761615/HDFS-9053.002.patch
|
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / 10ab7d5 |
| whitespace | https://builds.apache.org/job/PreCommit-HDFS-Build/12589/artifact/patchprocess/whitespace.txt
|
| hadoop-common test log | https://builds.apache.org/job/PreCommit-HDFS-Build/12589/artifact/patchprocess/testrun_hadoop-common.txt
|
| hadoop-hdfs test log | https://builds.apache.org/job/PreCommit-HDFS-Build/12589/artifact/patchprocess/testrun_hadoop-hdfs.txt
|
| Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/12589/testReport/ |
| Java | 1.7.0_55 |
| uname | Linux asf900.gq1.ygridcore.net 3.13.0-36-lowlatency #63-Ubuntu SMP PREEMPT Wed Sep
3 21:56:12 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux |
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/12589/console |


This message was automatically generated.

> Support large directories efficiently using B-Tree
> --------------------------------------------------
>
>                 Key: HDFS-9053
>                 URL: https://issues.apache.org/jira/browse/HDFS-9053
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: Yi Liu
>            Assignee: Yi Liu
>            Priority: Critical
>         Attachments: HDFS-9053 (BTree with simple benchmark).patch, HDFS-9053 (BTree).patch,
HDFS-9053.001.patch, HDFS-9053.002.patch
>
>
> This is a long standing issue, we were trying to improve this in the past.  Currently
we use an ArrayList for the children under a directory, and the children are ordered in the
list, for insert/delete/search, the time complexity is O(log n), but insertion/deleting causes
re-allocations and copies of big arrays, so the operations are costly.  For example, if the
children grow to 1M size, the ArrayList will resize to > 1M capacity, so need > 1M *
4bytes = 4M continuous heap memory, it easily causes full GC in HDFS cluster where namenode
heap memory is already highly used.  I recap the 3 main issues:
> # Insertion/deletion operations in large directories are expensive because re-allocations
and copies of big arrays.
> # Dynamically allocate several MB continuous heap memory which will be long-lived can
easily cause full GC problem.
> # Even most children are removed later, but the directory INode still occupies same size
heap memory, since the ArrayList will never shrink.
> This JIRA is similar to HDFS-7174 created by [~kihwal], but use B-Tree to solve the problem
suggested by [~shv]. 
> So the target of this JIRA is to implement a low memory footprint B-Tree and use it to
replace ArrayList. 
> If the elements size is not large (less than the maximum degree of B-Tree node), the
B-Tree only has one root node which contains an array for the elements. And if the size grows
large enough, it will split automatically, and if elements are removed, then B-Tree nodes
can merge automatically (see more: https://en.wikipedia.org/wiki/B-tree).  It will solve the
above 3 issues.



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