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https://issues.apache.org/jira/browse/HDFS-8160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14504154#comment-14504154
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Rod commented on HDFS-8160:
---------------------------

I wish the answer were that simple, here's some cluster status taken at the 
time of the issue which indicates all nodes were running healthy. Also, the 
operation ultimately did not fail.

3-node Apache Hadoop 2.5.2 cluster running on Ubuntu 14.04 

dfshealth overview:
Security is off.
Safemode is off.

8 files and directories, 9 blocks = 17 total filesystem object(s).

Heap Memory used 45.78 MB of 90.5 MB Heap Memory. Max Heap Memory is 889 MB.

Non Heap Memory used 36.3 MB of 70.44 MB Commited Non Heap Memory. Max Non Heap 
Memory is 130 MB.
Configured Capacity:    118.02 GB
DFS Used:       2.77 GB
Non DFS Used:   12.19 GB
DFS Remaining:  103.06 GB
DFS Used%:      2.35%
DFS Remaining%: 87.32%
Block Pool Used:        2.77 GB
Block Pool Used%:       2.35%
DataNodes usages% (Min/Median/Max/stdDev):      2.35% / 2.35% / 2.35% / 0.00%
Live Nodes      3 (Decommissioned: 0)
Dead Nodes      0 (Decommissioned: 0)
Decommissioning Nodes   0
Number of Under-Replicated Blocks       0
Number of Blocks Pending Deletion       0

Datanode Information
In operation
Node    Last contact    Admin State     Capacity        Used    Non DFS Used    
Remaining       Blocks  Block pool used Failed Volumes  Version
hadoop252-3 (x.x.x.10:50010)    1       In Service      39.34 GB        944.85 
MB       3.63 GB 34.79 GB        9       944.85 MB (2.35%)       0       2.5.2
hadoop252-1 (x.x.x.8:50010)     0       In Service      39.34 GB        944.85 
MB       4.94 GB 33.48 GB        9       944.85 MB (2.35%)       0       2.5.2
hadoop252-2 (x.x.x.9:50010)     1       In Service      39.34 GB        944.85 
MB       3.63 GB 34.79 GB        9       944.85 MB (2.35%)       0       2.5.2

> Long delays when calling hdfsOpenFile()
> ---------------------------------------
>
>                 Key: HDFS-8160
>                 URL: https://issues.apache.org/jira/browse/HDFS-8160
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: libhdfs
>    Affects Versions: 2.5.2
>         Environment: 3-node Apache Hadoop 2.5.2 cluster running on Ubuntu 
> 14.04 
> dfshealth overview:
> Security is off.
> Safemode is off.
> 8 files and directories, 9 blocks = 17 total filesystem object(s).
> Heap Memory used 45.78 MB of 90.5 MB Heap Memory. Max Heap Memory is 889 MB.
> Non Heap Memory used 36.3 MB of 70.44 MB Commited Non Heap Memory. Max Non 
> Heap Memory is 130 MB.
> Configured Capacity:  118.02 GB
> DFS Used:     2.77 GB
> Non DFS Used: 12.19 GB
> DFS Remaining:        103.06 GB
> DFS Used%:    2.35%
> DFS Remaining%:       87.32%
> Block Pool Used:      2.77 GB
> Block Pool Used%:     2.35%
> DataNodes usages% (Min/Median/Max/stdDev):    2.35% / 2.35% / 2.35% / 0.00%
> Live Nodes    3 (Decommissioned: 0)
> Dead Nodes    0 (Decommissioned: 0)
> Decommissioning Nodes 0
> Number of Under-Replicated Blocks     0
> Number of Blocks Pending Deletion     0
> Datanode Information
> In operation
> Node  Last contact    Admin State     Capacity        Used    Non DFS Used    
> Remaining       Blocks  Block pool used Failed Volumes  Version
> hadoop252-3 (x.x.x.10:50010)  1       In Service      39.34 GB        944.85 
> MB       3.63 GB 34.79 GB        9       944.85 MB (2.35%)       0       2.5.2
> hadoop252-1 (x.x.x.8:50010)   0       In Service      39.34 GB        944.85 
> MB       4.94 GB 33.48 GB        9       944.85 MB (2.35%)       0       2.5.2
> hadoop252-2 (x.x.x.9:50010)   1       In Service      39.34 GB        944.85 
> MB       3.63 GB 34.79 GB        9       944.85 MB (2.35%)       0       2.5.2
> java version "1.7.0_76"
> Java(TM) SE Runtime Environment (build 1.7.0_76-b13)
> Java HotSpot(TM) 64-Bit Server VM (build 24.76-b04, mixed mode)
>            Reporter: Rod
>
> Calling hdfsOpenFile on a file residing on target 3-node Hadoop cluster 
> (described in detail in Environment section) blocks for a long time (several 
> minutes).  I've noticed that the delay is related to the size of the target 
> file. 
> For example, attempting to hdfsOpenFile() on a file of filesize 852483361 
> took 121 seconds, but a file of 15458 took less than a second.
> Also, during the long delay, the following stacktrace is routed to standard 
> out:
> 2015-04-16 10:32:13,943 WARN  [main] hdfs.BlockReaderFactory 
> (BlockReaderFactory.java:getRemoteBlockReaderFromTcp(693)) - I/O error 
> constructing remote block reader.
> org.apache.hadoop.net.ConnectTimeoutException: 60000 millis timeout while 
> waiting for channel to be ready for connect. ch : 
> java.nio.channels.SocketChannel[connection-pending remote=/10.40.8.10:50010]
>       at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:533)
>       at 
> org.apache.hadoop.hdfs.DFSClient.newConnectedPeer(DFSClient.java:3101)
>       at 
> org.apache.hadoop.hdfs.BlockReaderFactory.nextTcpPeer(BlockReaderFactory.java:755)
>       at 
> org.apache.hadoop.hdfs.BlockReaderFactory.getRemoteBlockReaderFromTcp(BlockReaderFactory.java:670)
>       at 
> org.apache.hadoop.hdfs.BlockReaderFactory.build(BlockReaderFactory.java:337)
>       at 
> org.apache.hadoop.hdfs.DFSInputStream.blockSeekTo(DFSInputStream.java:576)
>       at 
> org.apache.hadoop.hdfs.DFSInputStream.readWithStrategy(DFSInputStream.java:800)
>       at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:854)
>       at 
> org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:143)
> 2015-04-16 10:32:13,946 WARN  [main] hdfs.DFSClient 
> (DFSInputStream.java:blockSeekTo(612)) - Failed to connect to 
> /10.40.8.10:50010 for block, add to deadNodes and continue. 
> org.apache.hadoop.net.ConnectTimeoutException: 60000 millis timeout while 
> waiting for channel to be ready for connect. ch : 
> java.nio.channels.SocketChannel[connection-pending remote=/10.40.8.10:50010]
> org.apache.hadoop.net.ConnectTimeoutException: 60000 millis timeout while 
> waiting for channel to be ready for connect. ch : 
> java.nio.channels.SocketChannel[connection-pending remote=/10.40.8.10:50010]
>       at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:533)
>       at 
> org.apache.hadoop.hdfs.DFSClient.newConnectedPeer(DFSClient.java:3101)
>       at 
> org.apache.hadoop.hdfs.BlockReaderFactory.nextTcpPeer(BlockReaderFactory.java:755)
>       at 
> org.apache.hadoop.hdfs.BlockReaderFactory.getRemoteBlockReaderFromTcp(BlockReaderFactory.java:670)
>       at 
> org.apache.hadoop.hdfs.BlockReaderFactory.build(BlockReaderFactory.java:337)
>       at 
> org.apache.hadoop.hdfs.DFSInputStream.blockSeekTo(DFSInputStream.java:576)
>       at 
> org.apache.hadoop.hdfs.DFSInputStream.readWithStrategy(DFSInputStream.java:800)
>       at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:854)
>       at 
> org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:143)
> I have also seen similar delays and stacktrace printout when executing dfs CL 
> commands on those same files (df -cat, df -tail, etc.).



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