Why Does DataNode Fail to Report Data Blocks?

Question

The DataNode is normal, but cannot report data blocks. As a result, the existing data blocks cannot be used.

Answer

This error may occur when the number of data blocks in a data directory exceeds four times the upper limit (4 x 1 MB). And the DataNode generates the following error logs:

2015-11-05 10:26:32,936 | ERROR | DataNode:[[[DISK]file:/srv/BigData/hadoop/data1/dn/]] heartbeating to 
vm-210/10.91.8.210:8020 | Exception in BPOfferService for Block pool BP-805114975-10.91.8.210-1446519981645 
(Datanode Uuid bcada350-0231-413b-bac0-8c65e906c1bb) service to vm-210/10.91.8.210:8020 | BPServiceActor.java:824 
java.lang.IllegalStateException:com.google.protobuf.InvalidProtocolBufferException:Protocol message was too large.May 
be malicious.Use CodedInputStream.setSizeLimit() to increase the size limit. at org.apache.hadoop.hdfs.protocol.BlockListAsLongs$BufferDecoder$1.next(BlockListAsLongs.java:369) 
at org.apache.hadoop.hdfs.protocol.BlockListAsLongs$BufferDecoder$1.next(BlockListAsLongs.java:347) at org.apache.hadoop.hdfs.
protocol.BlockListAsLongs$BufferDecoder.getBlockListAsLongs(BlockListAsLongs.java:325) at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB.
blockReport(DatanodeProtocolClientSideTranslatorPB.java:190) at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.blockReport(BPServiceActor.java:473) 
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.offerService(BPServiceActor.java:685) at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:822) 
at java.lang.Thread.run(Thread.java:745) Caused by:com.google.protobuf.InvalidProtocolBufferException:Protocol message was too large.May be malicious.Use CodedInputStream.setSizeLimit() 
to increase the size limit. at com.google.protobuf.InvalidProtocolBufferException.sizeLimitExceeded(InvalidProtocolBufferException.java:110) at com.google.protobuf.CodedInputStream.refillBuffer(CodedInputStream.java:755) 
at com.google.protobuf.CodedInputStream.readRawByte(CodedInputStream.java:769) at com.google.protobuf.CodedInputStream.readRawVarint64(CodedInputStream.java:462) at com.google.protobuf.
CodedInputStream.readSInt64(CodedInputStream.java:363) at org.apache.hadoop.hdfs.protocol.BlockListAsLongs$BufferDecoder$1.next(BlockListAsLongs.java:363)

The number of data blocks in the data directory is displayed as Metric. You can monitor its value through http://<datanode-ip>:<http-port>/jmx. If the value is greater than four times the upper limit (4 x 1 MB), you are advised to configure multiple drives and restart HDFS.

Recovery procedure:

1. Configure multiple data directories on the DataNode.

   For example, configure multiple directories on the DataNode where only the /data1/datadir directory is configured:

   <property> <name>dfs.datanode.data.dir</name> <value>/data1/datadir</value> </property>

   Configure as follows:

   <property> <name>dfs.datanode.data.dir</name> <value>/data1/datadir/,/data2/datadir,/data3/datadir</value> </property>

   

   You are advised to configure multiple data directories on multiple disks. Otherwise, performance may be affected.

2. Restart the HDFS.
3. Perform the following operation to move the data to the new data directory:

   mv/data1/datadir/current/finalized/subdir1 /data2/datadir/current/finalized/subdir1

4. Restart the HDFS.