下面是异常信息：

2018-11-08 16:55:52,361 INFO [main] org.apache.hadoop.hbase.mapreduce.TableRecordReaderImpl: recovered from org.apache.hadoop.hbase.client.RetriesExhaustedException: Failed after attempts=36, exceptions:
Thu Nov 08 16:55:52 CST 2018, null, java.net.SocketTimeoutException: callTimeout=180000, callDuration=180111: row '120180358862' on table 'ubas:stats_job_user_analysis' at region=ubas:stats_job_user_analysis,1\x11201803\x1158862,1536809361468.aa5027e279ba39d6505d8b507c6aa3a0., hostname=foxlog02.engine.wx,16020,1538805121280, seqNum=61831

	at org.apache.hadoop.hbase.client.RpcRetryingCallerWithReadReplicas.throwEnrichedException(RpcRetryingCallerWithReadReplicas.java:276)
	at org.apache.hadoop.hbase.client.ScannerCallableWithReplicas.call(ScannerCallableWithReplicas.java:210)
	at org.apache.hadoop.hbase.client.ScannerCallableWithReplicas.call(ScannerCallableWithReplicas.java:60)
	at org.apache.hadoop.hbase.client.RpcRetryingCaller.callWithoutRetries(RpcRetryingCaller.java:210)
	at org.apache.hadoop.hbase.client.ClientScanner.call(ClientScanner.java:327)
	at org.apache.hadoop.hbase.client.ClientScanner.loadCache(ClientScanner.java:413)
	at org.apache.hadoop.hbase.client.ClientScanner.next(ClientScanner.java:371)
	at org.apache.hadoop.hbase.mapreduce.TableRecordReaderImpl.nextKeyValue(TableRecordReaderImpl.java:210)
	at org.apache.hadoop.hbase.mapreduce.TableRecordReader.nextKeyValue(TableRecordReader.java:147)
	at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase$1.nextKeyValue(TableInputFormatBase.java:216)
	at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.nextKeyValue(MapTask.java:556)
	at org.apache.hadoop.mapreduce.task.MapContextImpl.nextKeyValue(MapContextImpl.java:80)
	at org.apache.hadoop.mapreduce.lib.map.WrappedMapper$Context.nextKeyValue(WrappedMapper.java:91)
	at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
	at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:787)
	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
	at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1758)
	at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.net.SocketTimeoutException: callTimeout=180000, callDuration=180111: row '120180358862' on table 'ubas:stats_job_user_analysis' at region=ubas:stats_job_user_analysis,1\x11201803\x1158862,1536809361468.aa5027e279ba39d6505d8b507c6aa3a0., hostname=foxlog02.engine.wx,16020,1538805121280, seqNum=61831
	at org.apache.hadoop.hbase.client.RpcRetryingCaller.callWithRetries(RpcRetryingCaller.java:169)
	at org.apache.hadoop.hbase.client.ResultBoundedCompletionService$QueueingFuture.run(ResultBoundedCompletionService.java:65)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.IOException: Call to FoxLog02.engine.wx/192.168.202.2:16020 failed on local exception: org.apache.hadoop.hbase.ipc.CallTimeoutException: Call id=2, waitTime=180001, operationTimeout=180000 expired.
	at org.apache.hadoop.hbase.ipc.AbstractRpcClient.wrapException(AbstractRpcClient.java:292)
	at org.apache.hadoop.hbase.ipc.RpcClientImpl.call(RpcClientImpl.java:1271)
	at org.apache.hadoop.hbase.ipc.AbstractRpcClient.callBlockingMethod(AbstractRpcClient.java:227)
	at org.apache.hadoop.hbase.ipc.AbstractRpcClient$BlockingRpcChannelImplementation.callBlockingMethod(AbstractRpcClient.java:336)
	at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$BlockingStub.scan(ClientProtos.java:34094)
	at org.apache.hadoop.hbase.client.ScannerCallable.call(ScannerCallable.java:220)
	at org.apache.hadoop.hbase.client.ScannerCallable.call(ScannerCallable.java:65)
	at org.apache.hadoop.hbase.client.RpcRetryingCaller.callWithoutRetries(RpcRetryingCaller.java:210)
	at org.apache.hadoop.hbase.client.ScannerCallableWithReplicas$RetryingRPC.call(ScannerCallableWithReplicas.java:364)
	at org.apache.hadoop.hbase.client.ScannerCallableWithReplicas$RetryingRPC.call(ScannerCallableWithReplicas.java:338)
	at org.apache.hadoop.hbase.client.RpcRetryingCaller.callWithRetries(RpcRetryingCaller.java:136)
	... 4 more
Caused by: org.apache.hadoop.hbase.ipc.CallTimeoutException: Call id=2, waitTime=180001, operationTimeout=180000 expired.
	at org.apache.hadoop.hbase.ipc.Call.checkAndSetTimeout(Call.java:73)
	at org.apache.hadoop.hbase.ipc.RpcClientImpl.call(RpcClientImpl.java:1245)
	... 13 more

2018-11-08 16:55:52,362 WARN [main] org.apache.hadoop.hbase.mapreduce.TableRecordReaderImpl: We are restarting the first next() invocation, if your mapper has restarted a few other times like this then you should consider killing this job and investigate why it's taking so long.
2018-11-08 17:01:45,893 INFO [main] com.tracker.offline.business.job.user.JobAnalMonthTopMR: count :0
2018-11-08 17:01:45,893 INFO [main] com.tracker.offline.business.job.user.JobAnalMonthTopMR: tablename execute end :ubas:stats_job_user_analysis
2018-11-08 17:04:45,896 WARN [main] org.apache.hadoop.hbase.client.ScannerCallable: Ignore, probably already closed

　代码设置参数：

　　　　　　　Scan scan = new Scan();
            scan.setAttribute(Scan.SCAN_ATTRIBUTES_TABLE_NAME, tablename.getBytes());
            scan.setCaching(2000);
            scan.setCacheBlocks(false);
            FilterList filter = new FilterList(FilterList.Operator.MUST_PASS_ONE);
            for(int i = 0 ; i<monthsList.size();i++){
                 for(int j=0 ; j<3 ;j++){
                     filter.addFilter(new PrefixFilter(Bytes.toBytes(j+RowUtil.ROW_SPLIT +monthsList.get(i))));
                 }
                scan.setFilter(filter);     
            }      
            HbaseMapReduce mr_1 = new HbaseMapReduce(JobAnalMonthTopMR.class, JobMonthMapper.class, Text.class, Text.class, trackerconfig, outputPath + "/01");
            mr_1.setReducerClass(JobMonthReducer.class)
            .setScan(scan).setParameter("hbase.client.scanner.timeout.period", "180000")
            .setParameter("hbase.rpc.timeout", "180000").setJarName("JobAnalMonthTopMR-statistic");
            mr_1.waitForCompletion();

代码的基本设置和出现的场景：

1-超时时长180s；

2-缓存条数2000条，每条三列，值为Long型；

3-被扫描表大小，54G；

4-有一个过滤器，使用的前缀查询；

5-刚迁移集群，以前是MapReduc和Hbase在同一个集群上。迁移后，Hbase和MapReduce不再同一个集群上；

排查原因：

1-查看表有没有被破坏，参考命令hbase hbck；

2-超时时长解决方法：

　　　（1）-增加超时时长；（2）-减少缓存条数；  但问题不再此处，因为取的每条数据很小，总的两千条也不会暂用很多的内存；

3-前缀过滤器原因：因为时过滤查询和前缀查询的速度比较慢。所以在扫描的块中分布的合格的条数比例很小时。

   会很难再短时间内读取2000条数据，解决方法，用范围查询代替前缀查询。