writing data to alluxio with CACHE_THROUGH is failing

Question

I am trying to write data to alluxio using map reduce. I have around 11 gig of data on hdfs which I am writing to alluxio.It is working fine with MUST_CACHE write type (the default value of alluxio.user.file.writetype.default).

But when I am trying to write it using CACHE_THROUGH, it is failing with following exception:

   Error: alluxio.exception.status.UnavailableException: Channel to <hostname of one of the  worker>:29999: <underfs path to file> (No such file or directory)
            at alluxio.client.block.stream.NettyPacketWriter.close(NettyPacketWriter.java:263)
            at com.google.common.io.Closer.close(Closer.java:206)
            at alluxio.client.block.stream.BlockOutStream.close(BlockOutStream.java:166)
            at alluxio.client.file.FileOutStream.close(FileOutStream.java:137)
            at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.close(FSDataOutputStream.java:72)
            at org.apache.hadoop.fs.FSDataOutputStream.close(FSDataOutputStream.java:106)
            at org.apache.hadoop.mapreduce.lib.output.TextOutputFormat$LineRecordWriter.close(TextOutputFormat.java:111)
            at org.apache.hadoop.mapred.MapTask$NewDirectOutputCollector.close(MapTask.java:679)
            at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:802)
            at org.apache.hadoop.mapred.MapTask.run(MapTask.java:346)
            at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163)
            at java.security.AccessController.doPrivileged(Native Method)
            at javax.security.auth.Subject.doAs(Subject.java:422)
            at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1595)
            at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
    Caused by: alluxio.exception.status.NotFoundException: Channel to <hostname of one of the  worker>29999: <underfs path to file> (No such file or directory)
            at alluxio.exception.status.AlluxioStatusException.from(AlluxioStatusException.java:153)
            at alluxio.util.CommonUtils.unwrapResponseFrom(CommonUtils.java:548)
            at alluxio.client.block.stream.NettyPacketWriter$PacketWriteHandler.channelRead(NettyPacketWriter.java:367)
            at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333)
            at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319)
            at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)
            at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333)
            at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319)
            at io.netty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:254)
            at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333)
            at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319)
            at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
            at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333)
            at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319)
            at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:163)
            at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333)
            at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319)
            at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787)
            at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:130)
            at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511)
            at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468)
            at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382)
            at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
            at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116)
            at java.lang.Thread.run(Thread.java:748)

I tried with below command as well, getting same error:

./alluxio fs -Dalluxio.user.file.writetype.default=CACHE_THROUGH copyFromLocal <hdfs_input_path> <alluxio_output_path>

Any help/pointers will be appreciated. Thanks

Answer 1

The copyFromLocal shell command is only able to copy files available on the local filesystem. To copy a file out of HDFS and into Alluxio, you can first copy the file to your local machine, then write the file to Alluxio.

hdfs dfs -get <hdfs_input_path> /tmp/tmp_file
alluxio fs copyFromLocal /tmp/tmp_file <alluxio_output_path>

To write directly from mapreduce to Alluxio, update your core-site.xml to contain

<property>
  <name>fs.alluxio.impl</name>
  <value>alluxio.hadoop.FileSystem</value>
  <description>The Alluxio FileSystem (Hadoop 1.x and 2.x)</description>
</property>
<property>
  <name>fs.AbstractFileSystem.alluxio.impl</name>
  <value>alluxio.hadoop.AlluxioFileSystem</value>
  <description>The Alluxio AbstractFileSystem (Hadoop 2.x)</description>
</property>

, add the Alluxio client jar to your application classpath with -libjars /path/to/client, and write to an alluxio://master_hostname:19998/alluxio_output_path URI. See the documentation for further details.