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Date: Wed, 8 Jun 2016 11:45:21 +0000 (UTC)
From: "Chris Machemer (JIRA)" <jira@apache.org>
To: hdfs-dev@hadoop.apache.org
Message-ID: <JIRA.12976839.1465386261000.26039.1465386321306@Atlassian.JIRA>
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Subject: [jira] [Created] (HDFS-10502) Enabled memory locking and now HDFS
 won't start up
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archived-at: Wed, 08 Jun 2016 11:45:24 -0000

Chris Machemer created HDFS-10502:
-------------------------------------

             Summary: Enabled memory locking and now HDFS won't start up
                 Key: HDFS-10502
                 URL: https://issues.apache.org/jira/browse/HDFS-10502
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: fs
    Affects Versions: 2.7.2
         Environment: RHEL 6.8
            Reporter: Chris Machemer


My goal is to speed up reads.  I have about 500k small files (2k to 15k) and I'm trying to use HDFS as a cache for serialized instances of java objects.

I've written the code to construct and serialize all the objects out to HDFS, and am now hoping to improve read performance, because accessing the objects from disk-based storage is proving to be too slow for my application's SLA's.

So my first question is, is using memory locking and hdfs cacheadmin pools and directives the right way to go, to cache my objects into memory, or should I create RAM disks, and do memory-based storage instead?

If hdfs cacheadmin is the way to go (it's the path I'm going down so far), then I need to figure out if what's happening is a bug or if I've configured something wrong, because when I start up HDFS with a gig of memory locked (both in limits.d for ulimit -l and also in hdfs-site.xml) and the server starts up, and presumably tries to cache things into memory, I get hours and hours of timeouts in the logs like this:

2016-06-08 07:42:50,856 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: IOException in offerService
java.net.SocketTimeoutException: Call From stgb-fe1.litle.com/10.1.9.66 to localhost:8020 failed on socket timeout exception: java.net.SocketTimeoutException: 60000 millis timeout while waiting for channel to be ready for read. ch : java.nio.channels.SocketChannel[connected local=/127.0.0.1:51647 remote=localhost/127.0.0.1:8020]; For more details see:  http://wiki.apache.org/hadoop/SocketTimeout
	at sun.reflect.GeneratedConstructorAccessor8.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:792)
	at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:751)
	at org.apache.hadoop.ipc.Client.call(Client.java:1479)
	at org.apache.hadoop.ipc.Client.call(Client.java:1412)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
	at com.sun.proxy.$Proxy13.sendHeartbeat(Unknown Source)
	at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB.sendHeartbeat(DatanodeProtocolClientSideTranslatorPB.java:153)
	at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.sendHeartBeat(BPServiceActor.java:554)
	at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.offerService(BPServiceActor.java:653)
	at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:824)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.SocketTimeoutException: 60000 millis timeout while waiting for channel to be ready for read. ch : java.nio.channels.SocketChannel[connected local=/127.0.0.1:51647 remote=localhost/127.0.0.1:8020]
	at org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:164)
	at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:161)
	at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:131)
	at java.io.FilterInputStream.read(FilterInputStream.java:133)
	at java.io.FilterInputStream.read(FilterInputStream.java:133)
	at org.apache.hadoop.ipc.Client$Connection$PingInputStream.read(Client.java:520)
	at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
	at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
	at java.io.DataInputStream.readInt(DataInputStream.java:387)
	at org.apache.hadoop.ipc.Client$Connection.receiveRpcResponse(Client.java:1084)
	at org.apache.hadoop.ipc.Client$Connection.run(Client.java:979)


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