2018-12-05 21:40:41,608 WARN com.zaxxer.hikari.proxy.ConnectionProxy: Connection com.mysql.jdbc.JDBC4Connection@38eaa46b (HikariPool-0) marked as broken because of SQLSTATE(08S01), ErrorCode(0).
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 4 milliseconds ago.  The last packet sent successfully to the server was 4 milliseconds ago.
        at sun.reflect.GeneratedConstructorAccessor48.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:411)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3102)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2991)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3532)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2002)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2163)
        at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2624)
        at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2127)
        at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2293)
        at com.zaxxer.hikari.proxy.PreparedStatementProxy.executeQuery(PreparedStatementProxy.java:44)
        at io.hops.metadata.ndb.mysqlserver.MySQLQueryHelper.execute(MySQLQueryHelper.java:167)
        at io.hops.metadata.ndb.mysqlserver.MySQLQueryHelper.executeIntAggrQuery(MySQLQueryHelper.java:120)
        at io.hops.metadata.ndb.mysqlserver.MySQLQueryHelper.countAll(MySQLQueryHelper.java:57)
        at io.hops.metadata.ndb.dalimpl.hdfs.UnderReplicatedBlockClusterj.countAll(UnderReplicatedBlockClusterj.java:175)
        at org.apache.hadoop.hdfs.server.blockmanagement.UnderReplicatedBlocks$2.performTask(UnderReplicatedBlocks.java:147)
        at io.hops.transaction.handler.LightWeightRequestHandler.execute(LightWeightRequestHandler.java:57)
        at io.hops.transaction.handler.RequestHandler.handle(RequestHandler.java:65)
        at io.hops.transaction.handler.RequestHandler.handle(RequestHandler.java:60)
        at org.apache.hadoop.hdfs.server.blockmanagement.UnderReplicatedBlocks.size(UnderReplicatedBlocks.java:149)
        at org.apache.hadoop.hdfs.server.blockmanagement.UnderReplicatedBlocks.chooseUnderReplicatedBlocksInt(UnderReplicatedBlocks.java:377)
        at org.apache.hadoop.hdfs.server.blockmanagement.UnderReplicatedBlocks.access$400(UnderReplicatedBlocks.java:85)
        at org.apache.hadoop.hdfs.server.blockmanagement.UnderReplicatedBlocks$6.performTask(UnderReplicatedBlocks.java:584)
        at io.hops.transaction.handler.TransactionalRequestHandler.execute(TransactionalRequestHandler.java:99)
        at io.hops.transaction.handler.HopsTransactionalRequestHandler.execute(HopsTransactionalRequestHandler.java:50)
        at io.hops.transaction.handler.RequestHandler.handle(RequestHandler.java:65)
        at io.hops.transaction.handler.RequestHandler.handle(RequestHandler.java:60)
        at org.apache.hadoop.hdfs.server.blockmanagement.UnderReplicatedBlocks.chooseUnderReplicatedBlocks(UnderReplicatedBlocks.java:586)
        at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeReplicationWork(BlockManager.java:1678)
        at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeDatanodeWork(BlockManager.java:4902)
        at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$ReplicationMonitor.run(BlockManager.java:4849)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2552)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3002)
        ... 29 more