2019-11-22 17:15:27,705 FATAL [IPC Server handler 13 on 44844] org.apache.hadoop.mapred.TaskAttemptListenerImpl: Task: attempt_1574410493054_0011_m_000000_0 - exited : java.lang.RuntimeException: java.lang.RuntimeException: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at org.apache.sqoop.mapreduce.db.DBInputFormat.setDbConf(DBInputFormat.java:170)
at org.apache.sqoop.mapreduce.db.DBInputFormat.setConf(DBInputFormat.java:161)
at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:73)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:133)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:755)
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:1920)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.lang.RuntimeException: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at org.apache.sqoop.mapreduce.db.DBInputFormat.getConnection(DBInputFormat.java:223)
at org.apache.sqoop.mapreduce.db.DBInputFormat.setDbConf(DBInputFormat.java:168)
... 10 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
原因分析
1、TiDB数据库连接驱动包（当前是用的 mysql数据库连接驱动包）版本与 CDH集群的 sqoop组件版本不兼容。
2、CDH集群中的单一节点可以访问 TiDB数据库，其它节点与 TiDB数据库主机网络不通（假如 CDH集群有5个节点，需要5个节点都可以与 mysql的主机网络互通）。
此次报错原因是第二点。
解决办法
1、更新兼容当前 TiDB数据库连接驱动包（当前是用的 mysql数据库连接驱动包）与 CDH集群的 sqoop组件版本的驱动包。
2、关闭 CDH集群节点访问 TiDB数据库主机的防火墙，使得 CDH集群主机任何节点都可以访问 TiDB数据库。
异常日志
2019-11-22 17:15:27,705 FATAL [IPC Server handler 13 on 44844] org.apache.hadoop.mapred.TaskAttemptListenerImpl: Task: attempt_1574410493054_0011_m_000000_0 - exited : java.lang.RuntimeException: java.lang.RuntimeException: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at org.apache.sqoop.mapreduce.db.DBInputFormat.setDbConf(DBInputFormat.java:170)
at org.apache.sqoop.mapreduce.db.DBInputFormat.setConf(DBInputFormat.java:161)
at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:73)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:133)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:755)
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:1920)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.lang.RuntimeException: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at org.apache.sqoop.mapreduce.db.DBInputFormat.getConnection(DBInputFormat.java:223)
at org.apache.sqoop.mapreduce.db.DBInputFormat.setDbConf(DBInputFormat.java:168)
... 10 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:348)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2391)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2428)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2213)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:797)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at org.apache.sqoop.mapreduce.db.DBConfiguration.getConnection(DBConfiguration.java:302)
at org.apache.sqoop.mapreduce.db.DBInputFormat.getConnection(DBInputFormat.java:216)
... 11 more
Caused by: java.net.ConnectException: Connection timed out (Connection timed out)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at java.net.Socket.<init>(Socket.java:434)
at java.net.Socket.<init>(Socket.java:244)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:257)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:298)
... 27 more