背景：mysql查询性能瓶颈，一般前提有很多查询超时导致这个问题
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.cj.protocol.FullReadInputStream.readFully(FullReadInputStream.java:67)
at com.mysql.cj.protocol.a.SimplePacketReader.readHeader(SimplePacketReader.java:63)
at com.mysql.cj.protocol.a.SimplePacketReader.readHeader(SimplePacketReader.java:45)
at com.mysql.cj.protocol.a.TimeTrackingPacketReader.readHeader(TimeTrackingPacketReader.java:52)
at com.mysql.cj.protocol.a.TimeTrackingPacketReader.readHeader(TimeTrackingPacketReader.java:41)
at com.mysql.cj.protocol.a.MultiPacketReader.readHeader(MultiPacketReader.java:54)
at com.mysql.cj.protocol.a.MultiPacketReader.readHeader(MultiPacketReader.java:44)
at com.mysql.cj.protocol.a.NativeProtocol.readMessage(NativeProtocol.java:538)
at com.mysql.cj.protocol.a.NativeProtocol.checkErrorMessage(NativeProtocol.java:708)
at com.mysql.cj.protocol.a.NativeProtocol.sendCommand(NativeProtocol.java:647)
at com.mysql.cj.protocol.a.NativeProtocol.sendQueryPacket(NativeProtocol.java:946)
at com.mysql.cj.NativeSession.execSQL(NativeSession.java:1075)
问题:出现并发查询超时mysql的cpu飙升，导致连接不可用，大量慢查询，或者大表修改表字段，创建索引等都会出现这个问题
java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30000ms.
解决：优先kill掉超时进程，最后慢慢优化慢sql
标签：cj,FullReadInputStream,java,mysql,protocol,NativeProtocol,com From： https://www.cnblogs.com/cgy-home/p/18369202