I don't think you will find any step-by-step instructions.
Somebody has already mentioned in replies below that secondary node is NOT
a fail-over node. You can read about it here:
http://wiki.apache.org/hadoop/FAQ#7
http://hadoop.apache.org/core/docs/current/hdfs_user_guide.html#Secondary+NameNode
In fact, Secondary NameNode is a checkpointer only: it cannot process
heartbeats from data-nodes or "ls" commands from hdfs clients.
You probably meant to do after NameNode failed on node1 is:
stop Secondary node on node2 and then start the real
NameNode on node2. You will also have to restart data-nodes to redirect
them to the new name-node.
Another way to model a fail-over is to play with the Backup node, which
is only available in trunk (not in 0.19, which you seem to be using), and
is supposed to replace secondary node in 0.21.
Backup node is a real name-node and it can start processing heartbeats
and client commands if you redirect them to the Backup node.
I guess nobody tried it yet. So please share your experience.
Regards,
--Konstantin
Rakhi Khatwani wrote:
Hi,
Thanks for the suggestions. but my scenario is a little different.
i am doin a POC on namenode failover.
i have a 5 cluster node setup in which one acts as a master, 3 acts as
slaves and the last one, the secondary node.
i start my hadoop dfs, write something into it... and later kill my
namenode. (tryin to produce a real worls scenario where my namenode fails
due to some hardware error).
so my aim is to start the secondary node as the primary m/c.
so tht the dfs is intact (by copyin the checkpoint info)
and all the slave pcs becoming the slaves of the secondary namenode now.
1. Can this be achieved without shuttin down the cluster?... i have read
this somewhere... but coudnt achieve it.
2. Whats the step by step instruction to achieve it?.. i hv google it, got a
lot of different opinions n m totally confused now.
Thanks,
Raakhi
On Tue, May 26, 2009 at 11:27 PM, Konstantin Shvachko <s...@yahoo-inc.com>wrote:
Hi Rakhi,
This is because your name-node is trying to -importCheckpoint from a
directory,
which is locked by secondary name-node.
The secondary node is also running in your case, right?
You should use -importCheckpoint as the last resort, when name-node's
directories
are damaged.
In regular case you start name-node with
./hadoop-daemon.sh start namenode
Thanks,
--Konstantin
Rakhi Khatwani wrote:
Hi,
I followed the instructions suggested by you all. but i still
come across this exception when i use the following command:
./hadoop-daemon.sh start namenode -importCheckpoint
the exception is as follows:
2009-05-26 14:43:48,004 INFO
org.apache.hadoop.hdfs.server.namenode.NameNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG: host = germapp/192.168.0.1
STARTUP_MSG: args = [-importCheckpoint]
STARTUP_MSG: version = 0.19.0
STARTUP_MSG: build =
https://svn.apache.org/repos/asf/hadoop/core/branches/branch-0.19 -r
713890; compiled by 'ndaley' on Fri Nov 14 03:12:29 UTC 2008
************************************************************/
2009-05-26 14:43:48,147 INFO org.apache.hadoop.ipc.metrics.RpcMetrics:
Initializing RPC Metrics with hostName=NameNode, port=44444
2009-05-26 14:43:48,154 INFO
org.apache.hadoop.hdfs.server.namenode.NameNode: Namenode up at:
germapp/192.168.0.1:44444
2009-05-26 14:43:48,160 INFO org.apache.hadoop.metrics.jvm.JvmMetrics:
Initializing JVM Metrics with processName=NameNode, sessionId=null
2009-05-26 14:43:48,166 INFO
org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics:
Initializing NameNodeMeterics using context
object:org.apache.hadoop.metrics.spi.NullContext
2009-05-26 14:43:48,316 INFO
org.apache.hadoop.hdfs.server.namenode.FSNamesystem:
fsOwner=ithurs,ithurs
2009-05-26 14:43:48,317 INFO
org.apache.hadoop.hdfs.server.namenode.FSNamesystem:
supergroup=supergroup
2009-05-26 14:43:48,317 INFO
org.apache.hadoop.hdfs.server.namenode.FSNamesystem:
isPermissionEnabled=true
2009-05-26 14:43:48,343 INFO
org.apache.hadoop.hdfs.server.namenode.metrics.FSNamesystemMetrics:
Initializing FSNamesystemMetrics using context
object:org.apache.hadoop.metrics.spi.NullContext
2009-05-26 14:43:48,347 INFO
org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Registered
FSNamesystemStatusMBean
2009-05-26 14:43:48,455 INFO
org.apache.hadoop.hdfs.server.common.Storage: Storage directory
/tmp/hadoop-ithurs/dfs/name is not formatted.
2009-05-26 14:43:48,455 INFO
org.apache.hadoop.hdfs.server.common.Storage: Formatting ...
2009-05-26 14:43:48,457 INFO
org.apache.hadoop.hdfs.server.common.Storage: Cannot lock storage
/tmp/hadoop-ithurs/dfs/namesecondary. The directory is already locked.
2009-05-26 14:43:48,460 ERROR
org.apache.hadoop.hdfs.server.namenode.FSNamesystem: FSNamesystem
initialization failed.
java.io.IOException: Cannot lock storage
/tmp/hadoop-ithurs/dfs/namesecondary. The directory is already locked.
at
org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.lock(Storage.java:510)
at
org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.analyzeStorage(Storage.java:363)
at
org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:273)
at
org.apache.hadoop.hdfs.server.namenode.FSImage.doImportCheckpoint(FSImage.java:504)
at
org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:344)
at
org.apache.hadoop.hdfs.server.namenode.FSDirectory.loadFSImage(FSDirectory.java:87)
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystem.initialize(FSNamesystem.java:311)
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:290)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:163)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:208)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:194)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:859)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:868)
2009-05-26 14:43:48,464 INFO org.apache.hadoop.ipc.Server: Stopping
server on 44444
2009-05-26 14:43:48,466 ERROR
org.apache.hadoop.hdfs.server.namenode.NameNode: java.io.IOException:
Cannot lock storage /tmp/hadoop-ithurs/dfs/namesecondary. The
directory is already locked.
at
org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.lock(Storage.java:510)
at
org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.analyzeStorage(Storage.java:363)
at
org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:273)
at
org.apache.hadoop.hdfs.server.namenode.FSImage.doImportCheckpoint(FSImage.java:504)
at
org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:344)
at
org.apache.hadoop.hdfs.server.namenode.FSDirectory.loadFSImage(FSDirectory.java:87)
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystem.initialize(FSNamesystem.java:311)
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:290)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:163)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:208)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:194)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:859)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:868)
2009-05-26 14:43:48,468 INFO
org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at germapp/192.168.0.1
************************************************************/
any pointers/suggestions?
Thanks,
Raakhi
On 5/20/09, Aaron Kimball <aa...@cloudera.com> wrote:
See this regarding instructions on configuring a 2NN on a separate
machine
from the NN:
http://www.cloudera.com/blog/2009/02/10/multi-host-secondarynamenode-configuration/
- Aaron
On Thu, May 14, 2009 at 10:42 AM, Koji Noguchi
<knogu...@yahoo-inc.com>wrote:
Before 0.19, fsimage/edits were on the same directory.
So whenever secondary finishes checkpointing, it copies back the fsimage
while namenode still kept on writing to the edits file.
Usually we observed some latency on the namenode side during that time.
HADOOP-3948 would probably help after 0.19 or later.
Koji
-----Original Message-----
From: Brian Bockelman [mailto:bbock...@cse.unl.edu]
Sent: Thursday, May 14, 2009 10:32 AM
To: core-user@hadoop.apache.org
Subject: Re: Setting up another machine as secondary node
Hey Koji,
It's an expensive operation - for the secondary namenode, not the
namenode itself, right? I don't particularly care if I stress out a
dedicated node that doesn't have to respond to queries ;)
Locally we checkpoint+backup fairly frequently (not 5 minutes ...
maybe less than the default hour) due to sheer paranoia of losing
metadata.
Brian
On May 14, 2009, at 12:25 PM, Koji Noguchi wrote:
The secondary namenode takes a snapshot
at 5 minute (configurable) intervals,
This is a bit too aggressive.
Checkpointing is still an expensive operation.
I'd say every hour or even every day.
Isn't the default 3600 seconds?
Koji
-----Original Message-----
From: jason hadoop [mailto:jason.had...@gmail.com]
Sent: Thursday, May 14, 2009 7:46 AM
To: core-user@hadoop.apache.org
Subject: Re: Setting up another machine as secondary node
any machine put in the conf/masters file becomes a secondary namenode.
At some point there was confusion on the safety of more than one
machine,
which I believe was settled, as many are safe.
The secondary namenode takes a snapshot at 5 minute (configurable)
intervals, rebuilds the fsimage and sends that back to the namenode.
There is some performance advantage of having it on the local machine,
and
some safety advantage of having it on an alternate machine.
Could someone who remembers speak up on the single vrs multiple
secondary
namenodes?
On Thu, May 14, 2009 at 6:07 AM, David Ritch <david.ri...@gmail.com>
wrote:
First of all, the secondary namenode is not a what you might think a
secondary is - it's not failover device. It does make a copy of the
filesystem metadata periodically, and it integrates the edits into
the
image. It does *not* provide failover.
Second, you specify its IP address in hadoop-site.xml. This is where
you
can override the defaults set in hadoop-default.xml.
dbr
On Thu, May 14, 2009 at 9:03 AM, Rakhi Khatwani
<rakhi.khatw...@gmail.com
wrote:
Hi,
I wanna set up a cluster of 5 nodes in such a way that
node1 - master
node2 - secondary namenode
node3 - slave
node4 - slave
node5 - slave
How do we go about that?
there is no property in hadoop-env where i can set the ip-address
for
secondary name node.
if i set node-1 and node-2 in masters, and when we start dfs, in
both the
m/cs, the namenode n secondary namenode processes r present. but i
think
only node1 is active.
n my namenode fail over operation fails.
ny suggesstions?
Regards,
Rakhi
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