I changed the ec2 scripts to have fs.default.name assigned to the public
hostname (instead of the private hostname).
Now I can submit jobs remotely via the socks proxy (the problem below is
resolved) - but the map tasks fail with an exception:
2009-05-14 07:30:34,913 INFO org.apache.hadoop.ipc.Client: Retrying connect to
server: ec2-75-101-199-45.compute-1.amazonaws.com/10.254.175.132:50001. Already
tried 9 time(s).
2009-05-14 07:30:34,914 WARN org.apache.hadoop.mapred.TaskTracker: Error
running child
java.io.IOException: Call to
ec2-75-101-199-45.compute-1.amazonaws.com/10.254.175.132:50001 failed on local
exception: Connection refused
at org.apache.hadoop.ipc.Client.call(Client.java:699)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:216)
at $Proxy1.getProtocolVersion(Unknown Source)
at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:319)
at
org.apache.hadoop.hdfs.DFSClient.createRPCNamenode(DFSClient.java:104)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:177)
at
org.apache.hadoop.hdfs.DistributedFileSystem.initialize(DistributedFileSystem.java:74)
at
org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1367)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:56)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1379)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:215)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:120)
at org.apache.hadoop.mapred.Child.main(Child.java:153)
strangely enough - job submissions from nodes within the ec2 cluster work just
fine. I looked at the job.xml files of jobs submitted locally and remotely and
don't see any relevant differences.
Totally foxed now.
Joydeep
-----Original Message-----
From: Joydeep Sen Sarma [mailto:jssa...@facebook.com]
Sent: Wednesday, May 13, 2009 9:38 PM
To: core-user@hadoop.apache.org
Cc: Tom White
Subject: RE: public IP for datanode on EC2
Thanks Philip. Very helpful (and great blog post)! This seems to make basic dfs
command line operations work just fine.
However - I am hitting a new error during job submission (running
hadoop-0.19.0):
2009-05-14 00:15:34,430 ERROR exec.ExecDriver
(SessionState.java:printError(279)) - Job Submission failed with exception
'java.net.UnknownHostException(unknown host:
domU-12-31-39-00-51-94.compute-1.internal)'
java.net.UnknownHostException: unknown host:
domU-12-31-39-00-51-94.compute-1.internal
at org.apache.hadoop.ipc.Client$Connection.<init>(Client.java:195)
at org.apache.hadoop.ipc.Client.getConnection(Client.java:791)
at org.apache.hadoop.ipc.Client.call(Client.java:686)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:216)
at $Proxy0.getProtocolVersion(Unknown Source)
at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:348)
at
org.apache.hadoop.hdfs.DFSClient.createRPCNamenode(DFSClient.java:104)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:176)
at
org.apache.hadoop.hdfs.DistributedFileSystem.initialize(DistributedFileSystem.java:75)
at
org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1367)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:56)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1379)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:215)
at org.apache.hadoop.fs.Path.getFileSystem(Path.java:175)
at org.apache.hadoop.mapred.JobClient.getFs(JobClient.java:469)
at
org.apache.hadoop.mapred.JobClient.configureCommandLineOptions(JobClient.java:603)
at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:788)
looking at the stack trace and the code - it seems that this is happening
because the jobclient asks for the mapred system directory from the jobtracker
- which replies back with a path name that's qualified against the
fs.default.name setting of the jobtracker. Unfortunately the standard EC2
scripts assign this to the internal hostname of the hadoop master.
Is there any downside to using public hostnames instead of the private ones in
the ec2 starter scripts?
Thanks for the help,
Joydeep
-----Original Message-----
From: Philip Zeyliger [mailto:phi...@cloudera.com]
Sent: Wednesday, May 13, 2009 2:40 PM
To: core-user@hadoop.apache.org
Subject: Re: public IP for datanode on EC2
On Tue, May 12, 2009 at 9:11 PM, Joydeep Sen Sarma <jssa...@facebook.com> wrote:
> (raking up real old thread)
>
> After struggling with this issue for sometime now - it seems that accessing
> hdfs on ec2 from outside ec2 is not possible.
>
> This is primarily because of
> https://issues.apache.org/jira/browse/HADOOP-985. Even if datanode ports are
> authorized in ec2 and we set the public hostname via slave.host.name - the
> namenode uses the internal IP address of the datanodes for block locations.
> DFS clients outside ec2 cannot reach these addresses and report failure
> reading/writing data blocks.
>
> HDFS/EC2 gurus - would it be reasonable to ask for an option to not use IP
> addresses (and use datanode host names as pre-985)?
>
> I really like the idea of being able to use an external node (my personal
> workstation) to do job submission (which typically requires interacting with
> HDFS in order to push files into the jobcache etc). This way I don't need
> custom AMIs - I can use stock hadoop amis (all the custom software is on the
> external node). Without the above option - this is not possible currently.
You could use ssh to set up a SOCKS proxy between your machine and
ec2, and setup org.apache.hadoop.net.SocksSocketFactory to be the
socket factory.
http://www.cloudera.com/blog/2008/12/03/securing-a-hadoop-cluster-through-a-gateway/
has more information.
-- Philip
