MysqlWriter startWrite时获取连接hung住

目的：从hbase迁移大量数据到mysql，运行一段时间后speed变成0，先速度降低，大约15min后，变成0.不清楚为啥获取数据库连接会block

使用arthas分析：
datax writer线程12205获取链接hung死。
datax reader线程12206会使用到PrintStream，然后因为12205一直在占用锁，所以PrintStream一直没有释放。所以被12205阻塞
另外一个writer线程12435，因为com.alibaba.datax.plugin.rdbms.util.DBUtil.connect(DBUtil.java:361)方法有加锁，所以也会被12205这个线程阻塞

初步怀疑有脏数据导致回滚，然后卡死，不知道如何解决

[arthas@4252]$ thread 12205
"0-0-16-writer" Id=12205 RUNNABLE (in native)
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:326)
at java.io.BufferedOutputStream.write(BufferedOutputStream.java:122)
at java.io.PrintStream.write(PrintStream.java:480)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:291)
at sun.nio.cs.StreamEncoder.flushBuffer(StreamEncoder.java:104)
at java.io.OutputStreamWriter.flushBuffer(OutputStreamWriter.java:185)
at java.io.PrintStream.write(PrintStream.java:527)
at java.io.PrintStream.print(PrintStream.java:669)
at java.io.PrintStream.println(PrintStream.java:806)
at com.mysql.jdbc.log.StandardLogger.logInternal(StandardLogger.java:318)
at com.mysql.jdbc.log.StandardLogger.logWarn(StandardLogger.java:240)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1177)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2199)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2230)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2025)
at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:778)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:47)
at sun.reflect.GeneratedConstructorAccessor12.newInstance(Unknown Source)
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:425)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:386)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:208)
at com.alibaba.datax.plugin.rdbms.util.DBUtil.connect(DBUtil.java:392)
at com.alibaba.datax.plugin.rdbms.util.DBUtil.connect(DBUtil.java:384)
at com.alibaba.datax.plugin.rdbms.util.DBUtil.access$000(DBUtil.java:22)
at com.alibaba.datax.plugin.rdbms.util.DBUtil$3.call(DBUtil.java:322)
at com.alibaba.datax.plugin.rdbms.util.DBUtil$3.call(DBUtil.java:319)
at com.alibaba.datax.common.util.RetryUtil$Retry.call(RetryUtil.java:164)
at com.alibaba.datax.common.util.RetryUtil$Retry.doRetry(RetryUtil.java:111)
at com.alibaba.datax.common.util.RetryUtil.executeWithRetry(RetryUtil.java:30)
at com.alibaba.datax.plugin.rdbms.util.DBUtil.getConnection(DBUtil.java:319)
at com.alibaba.datax.plugin.rdbms.util.DBUtil.getConnection(DBUtil.java:303)
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.prepare(CommonRdbmsWriter.java:245)
at com.alibaba.datax.plugin.writer.mysqlwriter.MysqlWriter$Task.prepare(MysqlWriter.java:73)
at com.alibaba.datax.core.taskgroup.runner.WriterRunner.run(WriterRunner.java:50)
at java.lang.Thread.run(Thread.java:748)

[arthas@4252]$ thread 12206
"0-0-16-reader" Id=12206 BLOCKED on java.io.PrintStream@2ab4bc79 owned by "0-0-16-writer" Id=12205
at java.io.PrintStream.write(PrintStream.java:479)
- blocked on java.io.PrintStream@2ab4bc79
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:291)
at sun.nio.cs.StreamEncoder.implFlush(StreamEncoder.java:295)
at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:141)
at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:229)
at java.util.logging.StreamHandler.flush(StreamHandler.java:259)
at java.util.logging.ConsoleHandler.publish(ConsoleHandler.java:117)
at java.util.logging.Logger.log(Logger.java:738)
at java.util.logging.Logger.doLog(Logger.java:765)
at java.util.logging.Logger.logp(Logger.java:931)
at org.apache.commons.logging.impl.Jdk14Logger.log(Jdk14Logger.java:99)
at org.apache.commons.logging.impl.Jdk14Logger.info(Jdk14Logger.java:194)
at org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper.(RecoverableZooKeeper.java:120)
at org.apache.hadoop.hbase.zookeeper.ZKUtil.connect(ZKUtil.java:155)
at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.(ZooKeeperWatcher.java:175)
at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.(ZooKeeperWatcher.java:143)
at org.apache.hadoop.hbase.client.ZooKeeperKeepAliveConnection.(ZooKeeperKeepAliveConnection.java:43)
at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.getKeepAliveZooKeeperWatcher(ConnectionManager.java:1657)
at org.apache.hadoop.hbase.client.ZooKeeperRegistry.getClusterId(ZooKeeperRegistry.java:104)
at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.retrieveClusterId(ConnectionManager.java:880)
at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.(ConnectionManager.java:636)
at sun.reflect.GeneratedConstructorAccessor15.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.apache.hadoop.hbase.client.ConnectionFactory.createConnection(ConnectionFactory.java:238)
at org.apache.hadoop.hbase.client.ConnectionFactory.createConnection(ConnectionFactory.java:218)
at org.apache.hadoop.hbase.client.ConnectionFactory.createConnection(ConnectionFactory.java:181)
at com.alibaba.datax.plugin.reader.hbase11xreader.Hbase11xHelper.getHbaseConnection(Hbase11xHelper.java:56)
at com.alibaba.datax.plugin.reader.hbase11xreader.Hbase11xHelper.getTable(Hbase11xHelper.java:68)
at com.alibaba.datax.plugin.reader.hbase11xreader.HbaseAbstractTask.(HbaseAbstractTask.java:35)
at com.alibaba.datax.plugin.reader.hbase11xreader.MultiVersionTask.(MultiVersionTask.java:29)
at com.alibaba.datax.plugin.reader.hbase11xreader.MultiVersionFixedColumnTask.(MultiVersionFixedColumnTask.java:13)
at com.alibaba.datax.plugin.reader.hbase11xreader.Hbase11xReader$Task.init(Hbase11xReader.java:55)
at com.alibaba.datax.core.taskgroup.runner.ReaderRunner.run(ReaderRunner.java:45)
at java.lang.Thread.run(Thread.java:748)

[arthas@4252]$ thread 12435
"0-0-25-writer" Id=12435 BLOCKED on java.lang.Class@66099d27 owned by "0-0-16-writer" Id=12205
at com.alibaba.datax.plugin.rdbms.util.DBUtil.connect(DBUtil.java:361)
- blocked on java.lang.Class@66099d27
at com.alibaba.datax.plugin.rdbms.util.DBUtil.access$000(DBUtil.java:22)
at com.alibaba.datax.plugin.rdbms.util.DBUtil$3.call(DBUtil.java:322)
at com.alibaba.datax.plugin.rdbms.util.DBUtil$3.call(DBUtil.java:319)
at com.alibaba.datax.common.util.RetryUtil$Retry.call(RetryUtil.java:164)
at com.alibaba.datax.common.util.RetryUtil$Retry.doRetry(RetryUtil.java:111)
at com.alibaba.datax.common.util.RetryUtil.executeWithRetry(RetryUtil.java:30)
at com.alibaba.datax.plugin.rdbms.util.DBUtil.getConnection(DBUtil.java:319)
at com.alibaba.datax.plugin.rdbms.util.DBUtil.getConnection(DBUtil.java:303)
at com.alibaba.datax.plugin.rdbms.writer.CommonRdbmsWriter$Task.prepare(CommonRdbmsWriter.java:245)
at com.alibaba.datax.plugin.writer.mysqlwriter.MysqlWriter$Task.prepare(MysqlWriter.java:73)
at com.alibaba.datax.core.taskgroup.runner.WriterRunner.run(WriterRunner.java:50)
at java.lang.Thread.run(Thread.java:748)

Start by reviewing DBUtil.java at lines 319, 361, 384, and 392, then trace MysqlWriter.java Task.prepare and the HBase path through Hbase11xHelper.java. Reproduce the HBase-to-MySQL run if possible and compare the reported thread stacks; done should include a confirmed cause and evidence that connection acquisition no longer hangs.

Written by the indexing model from the issue text.