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From Enis Söztutar <e...@apache.org>
Subject Re: Parallel scanning of snapshots using hbase client api
Date Thu, 07 Jan 2016 11:46:44 GMT
TableSnapshotScanner itself does not support more than one scanner. Are you
creating more than 1 TableSnapshotScanner in your parallel scan?

Everytime a snapshot scanner is initiated, it will try to "restore" the
snapshot to a temporary location out of the regular root directory in hdfs.
You can try to give different restore directories to each
TableSnapshotScanner.

Enis

On Wed, Jan 6, 2016 at 5:51 PM, dbhogle <dbhogle@connexity.com> wrote:

> Using the client api, we can scan the snapshot using a single scanner. We
> currently create an instance of TableSnapshotScanner providing it with a
> unique dir location per scanner. We are currently on cdh 5.4.5 and using
> the
> hbase 1.0.0-cdh5.4.5 api. In order to get desired throughput, we tried to
> increase the number of parallel scanners but raising the no. of scanner
> instances throws the following exception, the occurrence increases as the
> no. of scanners goes up.
> Can the client api support multiple scanners for a single snapshot?
>
> java.io.IOException: java.util.concurrent.ExecutionException:
>
> org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException):
> failed to create file
>
> /hbase/archive/data/default/<tableName>/cb794cfb7948ba8b1f4e73b690dfbfe5/L/.links-a04e1a5b2141445eb1b9e2429f1eced2/cb794cfb7948ba8b1f4e73b690dfbfe5.<tableName>
> for DFSClient_NONMAPREDUCE_672650916_1 for client 10.10.2.90 because
> current
> leaseholder is trying to recreate file.
>         at
>
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.recoverLeaseInternal(FSNamesystem.java:3077)
>         at
>
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFileInternal(FSNamesystem.java:2783)
>         at
>
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFileInt(FSNamesystem.java:2676)
>         at
>
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFile(FSNamesystem.java:2560)
>         at
>
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.create(NameNodeRpcServer.java:585)
>         at
>
> org.apache.hadoop.hdfs.server.namenode.AuthorizationProviderProxyClientProtocol.create(AuthorizationProviderProxyClientProtocol.java:110)
>         at
>
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.create(ClientNamenodeProtocolServerSideTranslatorPB.java:395)
>         at
>
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
>         at
>
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:619)
>         at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1060)
>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2044)
>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2040)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at javax.security.auth.Subject.doAs(Subject.java:415)
>         at
>
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1671)
>         at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2038)
>
>         at
>
> org.apache.hadoop.hbase.util.ModifyRegionUtils.createRegions(ModifyRegionUtils.java:162)
>         at
>
> org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper.cloneHdfsRegions(RestoreSnapshotHelper.java:561)
>         at
>
> org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper.restoreHdfsRegions(RestoreSnapshotHelper.java:237)
>         at
>
> org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper.restoreHdfsRegions(RestoreSnapshotHelper.java:159)
>         at
>
> org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper.copySnapshotForScanner(RestoreSnapshotHelper.java:812)
>         at
>
> org.apache.hadoop.hbase.client.TableSnapshotScanner.init(TableSnapshotScanner.java:156)
>         at
>
> org.apache.hadoop.hbase.client.TableSnapshotScanner.<init>(TableSnapshotScanner.java:124)
>         at
>
> org.apache.hadoop.hbase.client.TableSnapshotScanner.<init>(TableSnapshotScanner.java:101)
>         at
> net.connexity.aro.data.AudienceScanner.join(AudienceScanner.scala:68)
>         at
> net.connexity.aro.actor.ScanActor.joinAudience(ScanActor.scala:190)
>         at
>
> net.connexity.aro.actor.ScanActor$$anonfun$receive$1.applyOrElse(ScanActor.scala:90)
>         at akka.actor.Actor$class.aroundReceive(Actor.scala:467)
>         at
> net.connexity.aro.actor.ScanActor.aroundReceive(ScanActor.scala:36)
>         at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
>         at akka.actor.ActorCell.invoke(ActorCell.scala:487)
>         at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238)
>         at akka.dispatch.Mailbox.run(Mailbox.scala:220)
>         at
>
> akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397)
>         at
> scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
>         at
>
> scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
>         at
> scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
>         at
>
> scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
>
>
>
> --
> View this message in context:
> http://apache-hbase.679495.n3.nabble.com/Parallel-scanning-of-snapshots-using-hbase-client-api-tp4077014.html
> Sent from the HBase Developer mailing list archive at Nabble.com.
>

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