The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
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:1121)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:357)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2484)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2521)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2306)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:839)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:49)
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:421)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:350)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at org.apache.sqoop.manager.SqlManager.makeConnection(SqlManager.java:903)
at org.apache.sqoop.manager.GenericJdbcManager.getConnection(GenericJdbcManager.java:59)
at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:762)
at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:785)
at org.apache.sqoop.manager.SqlManager.getColumnInfoForRawQuery(SqlManager.java:288)
at org.apache.sqoop.manager.SqlManager.getColumnTypesForRawQuery(SqlManager.java:259)
at org.apache.sqoop.manager.SqlManager.getColumnTypesForQuery(SqlManager.java:252)
at org.apache.sqoop.manager.ConnManager.getColumnTypes(ConnManager.java:343)
at org.apache.sqoop.orm.ClassWriter.getColumnTypes(ClassWriter.java:1879)
at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1672)
at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:106)
at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:524)
at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:655)
at org.apache.sqoop.Sqoop.run(Sqoop.java:151)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:76)
at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:187)
at org.apache.sqoop.Sqoop.runTool(Sqoop.java:241)
at org.apache.sqoop.Sqoop.runTool(Sqoop.java:250)
at org.apache.sqoop.Sqoop.main(Sqoop.java:259)
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:476)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:218)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:394)
at java.net.Socket.connect(Socket.java:606)
at java.net.Socket.connect(Socket.java:555)
at java.net.Socket.<init>(Socket.java:451)
at java.net.Socket.<init>(Socket.java:261)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:259)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:307)
... 33 more
21/04/19 08:51:22 ERROR tool.ImportTool: Import failed: java.io.IOException: No columns to generate for ClassWriter
at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1678)
at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:106)
at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:524)
at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:655)
at org.apache.sqoop.Sqoop.run(Sqoop.java:151)
[INFO] 2021-04-19 08:51:24.917 - [taskAppId=TASK-1-96-1406]:[127] - -> at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:76)
at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:187)
at org.apache.sqoop.Sqoop.runTool(Sqoop.java:241)
at org.apache.sqoop.Sqoop.runTool(Sqoop.java:250)
at org.apache.sqoop.Sqoop.main(Sqoop.java:259)
由于从两个不同mysql抽数据，没注意其中一台被dba弄挂了，导致链接失败。
一般连接失败先检查数据库状态，重启一下服务就行。