[ 
https://issues.apache.org/jira/browse/HBASE-8778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13715575#comment-13715575
 ] 

Hadoop QA commented on HBASE-8778:
----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest 
attachment 
  http://issues.apache.org/jira/secure/attachment/12593576/8778-dirmodtime.txt
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author 
tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include 
any new or modified tests.
                        Please justify why no new tests are needed for this 
patch.
                        Also please list what manual steps were performed to 
verify this patch.

    {color:green}+1 hadoop1.0{color}.  The patch compiles against the hadoop 
1.0 profile.

    {color:green}+1 hadoop2.0{color}.  The patch compiles against the hadoop 
2.0 profile.

    {color:green}+1 javadoc{color}.  The javadoc tool did not generate any 
warning messages.

    {color:green}+1 javac{color}.  The applied patch does not increase the 
total number of javac compiler warnings.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new 
Findbugs (version 1.3.9) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase 
the total number of release audit warnings.

    {color:green}+1 lineLengths{color}.  The patch does not introduce lines 
longer than 100

  {color:green}+1 site{color}.  The mvn site goal succeeds with this patch.

    {color:green}+1 core tests{color}.  The patch passed unit tests in .

Test results: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//testReport/
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-prefix-tree.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-client.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-common.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-protocol.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-server.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop1-compat.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-examples.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop-compat.html
Console output: 
https://builds.apache.org/job/PreCommit-HBASE-Build/6424//console

This message is automatically generated.
                
> Region assigments scan table directory making them slow for huge tables
> -----------------------------------------------------------------------
>
>                 Key: HBASE-8778
>                 URL: https://issues.apache.org/jira/browse/HBASE-8778
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Dave Latham
>            Assignee: Dave Latham
>             Fix For: 0.98.0, 0.95.2, 0.94.11
>
>         Attachments: 8778-dirmodtime.txt, HBASE-8778-0.94.5.patch, 
> HBASE-8778-0.94.5-v2.patch
>
>
> On a table with 130k regions it takes about 3 seconds for a region server to 
> open a region once it has been assigned.
> Watching the threads for a region server running 0.94.5 that is opening many 
> such regions shows the thread opening the reigon in code like this:
> {noformat}
> "PRI IPC Server handler 4 on 60020" daemon prio=10 tid=0x00002aaac07e9000 
> nid=0x6566 runnable [0x000000004c46d000]
>    java.lang.Thread.State: RUNNABLE
>         at java.lang.String.indexOf(String.java:1521)
>         at java.net.URI$Parser.scan(URI.java:2912)
>         at java.net.URI$Parser.parse(URI.java:3004)
>         at java.net.URI.<init>(URI.java:736)
>         at org.apache.hadoop.fs.Path.initialize(Path.java:145)
>         at org.apache.hadoop.fs.Path.<init>(Path.java:126)
>         at org.apache.hadoop.fs.Path.<init>(Path.java:50)
>         at 
> org.apache.hadoop.hdfs.protocol.HdfsFileStatus.getFullPath(HdfsFileStatus.java:215)
>         at 
> org.apache.hadoop.hdfs.DistributedFileSystem.makeQualified(DistributedFileSystem.java:252)
>         at 
> org.apache.hadoop.hdfs.DistributedFileSystem.listStatus(DistributedFileSystem.java:311)
>         at 
> org.apache.hadoop.fs.FilterFileSystem.listStatus(FilterFileSystem.java:159)
>         at org.apache.hadoop.fs.FileSystem.listStatus(FileSystem.java:842)
>         at org.apache.hadoop.fs.FileSystem.listStatus(FileSystem.java:867)
>         at org.apache.hadoop.hbase.util.FSUtils.listStatus(FSUtils.java:1168)
>         at 
> org.apache.hadoop.hbase.util.FSTableDescriptors.getTableInfoPath(FSTableDescriptors.java:269)
>         at 
> org.apache.hadoop.hbase.util.FSTableDescriptors.getTableInfoPath(FSTableDescriptors.java:255)
>         at 
> org.apache.hadoop.hbase.util.FSTableDescriptors.getTableInfoModtime(FSTableDescriptors.java:368)
>         at 
> org.apache.hadoop.hbase.util.FSTableDescriptors.get(FSTableDescriptors.java:155)
>         at 
> org.apache.hadoop.hbase.util.FSTableDescriptors.get(FSTableDescriptors.java:126)
>         at 
> org.apache.hadoop.hbase.regionserver.HRegionServer.openRegion(HRegionServer.java:2834)
>         at 
> org.apache.hadoop.hbase.regionserver.HRegionServer.openRegion(HRegionServer.java:2807)
>         at sun.reflect.GeneratedMethodAccessor64.invoke(Unknown Source)
>         at 
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>         at java.lang.reflect.Method.invoke(Method.java:597)
>         at 
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:320)
>         at 
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1426)
> {noformat}
> To open the region, the region server first loads the latest 
> HTableDescriptor.  Since HBASE-4553 HTableDescriptor's are stored in the file 
> system at "/hbase/<tableDir>/.tableinfo.<sequenceNum>".  The file with the 
> largest sequenceNum is the current descriptor.  This is done so that the 
> current descirptor is updated atomically.  However, since the filename is not 
> known in advance FSTableDescriptors it has to do a FileSystem.listStatus 
> operation which has to list all files in the directory to find it.  The 
> directory also contains all the region directories, so in our case it has to 
> load 130k FileStatus objects.  Even using a globStatus matching function 
> still transfers all the objects to the client before performing the pattern 
> matching.  Furthermore HDFS uses a default of transferring 1000 directory 
> entries in each RPC call, so it requires 130 roundtrips to the namenode to 
> fetch all the directory entries.
> Consequently, to reassign all the regions of a table (or a constant fraction 
> thereof) requires time proportional to the square of the number of regions.
> In our case, if a region server fails with 200 such regions, it takes 10+ 
> minutes for them all to be reassigned, after the zk expiration and log 
> splitting.

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