在对Hbase进行Scan的时候有时候会抛出ScannerTimeoutException，场景如下：
2012 15:28:52 (14mins, 41sec) org.apache.Hadoop.hbase.client.ScannerTimeoutException: 60622ms passed since the last invocation, timeout is currently set to 60000 at org.apache.hadoop.hbase.client.HTable$ClientScanner.next(HTable.java:1196) at org.apache.hadoop.hbase.mapreduce.TableRecordReaderImpl.nextKeyValue(TableRecordReaderImpl.java:133) at org.apache.hadoop.hbase.mapreduce.TableRecordReader.nextKeyValue(TableRecordReader.java:142) at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.nextKeyValue(MapTask.java:532) at org.apache.hadoop.mapreduce.MapContext.nextKeyValue(MapContext.java:67) at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:143) at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:764) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:370) at org.apache.hadoop.mapred.Child$4.run(Child.java:255) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:396) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1093) at org.apache.hadoop.mapred.Child.main(Child.java:249)原因查看步骤：
查找源码如下：
long timeout = lastNext + scannerTimeout; // If we are over the timeout, throw this exception to the client // Else, it's because the region moved and we used the old id // against the new region server; reset the scanner. if (timeout < System.currentTimeMillis()) { long elapsed = System.currentTimeMillis() - lastNext; ScannerTimeoutException ex = new ScannerTimeoutException( elapsed + "ms passed since the last invocation, " + "timeout is currently set to " + scannerTimeout); ex.initCause(e); throw ex; }核实下如下代码
long timeout = lastNext + scannerTimeout;
得出：ClientScanner.lastNext和HTable.scannerTimeout