java Cassandra驱动程序异常“所有主机尝试查询失败”每隔几个小时发生一次，无需解释
我的Cassandra集群（4节点集群）有问题。Cassandra版本为2.2.9，驱动程序版本为3.0.3
几个小时后（~3小时），我在驱动程序日志中看到以下问题：
- OutOfDirectMemoryError（偶尔发生，大部分时间没有影响）
- 没有与整数版本匹配的协议版本
- 未知响应操作码
- 心跳查询超时
- 尝试查询的所有主机均失败-->；不能再问卡桑德拉了
Cassandra集群是健康的，当我重新启动应用程序时，所有东西都会在几个小时内再次工作
日志片段：
First Time Count Message
2017-11-11 19:03:03 +0100 51 [/??.???.??.??:????] preparing to open ? new connections, total = ???
2017-11-11 19:03:03 +0100 49 [/??.???.??.??:????] Connection[/??.???.??.??:????-???, inFlight=?, closed=false] Transport initialized, connection ready
2017-11-11 19:03:03 +0100 24 [/??.???.??.??:????] Connection[/??.???.??.??:????-???, inFlight=?, closed=true] closed, remaining = ???
2017-11-11 19:03:29 +0100 1 Defuncting Connection[/??.???.??.??:????-???, inFlight=???, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: io.netty.util.internal.OutOfDirectMemoryError: failed to allocate ??????? byte(s) of direct memory (used: ???????, max: ????????))
2017-11-11 19:03:29 +0100 14 [/??.???.??.??:????] Connection[/??.???.??.??:????-???, inFlight=???, closed=false] failed, remaining = ???
2017-11-11 19:03:29 +0100 7 [/??.???.??.??:????] Connection[/??.???.??.??:????-???, inFlight=??, closed=false] failed, remaining = ???
2017-11-11 19:03:29 +0100 1 Defuncting Connection[/??.???.??.??:????-???, inFlight=??, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: java.lang.IllegalArgumentException: No protocol version matching integer version ?)
2017-11-11 19:03:29 +0100 5 Defuncting Connection[/??.???.??.??:????-???, inFlight=??, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: com.datastax.driver.core.exceptions.DriverInternalError: Unknown response opcode ??)
2017-11-11 19:03:29 +0100 4 Defuncting Connection[/??.???.??.??:????-???, inFlight=???, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: com.datastax.driver.core.exceptions.DriverInternalError: Unknown response opcode ?)
2017-11-11 19:03:29 +0100 3 Defuncting Connection[/??.???.??.??:????-???, inFlight=???, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: com.datastax.driver.core.exceptions.DriverInternalError: Unknown response opcode -???)
2017-11-11 19:03:30 +0100 3 Defuncting Connection[/??.???.??.??:????-???, inFlight=???, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: com.datastax.driver.core.exceptions.DriverInternalError: Unknown response opcode ??)
2017-11-11 19:03:30 +0100 2 Defuncting Connection[/??.???.??.??:????-???, inFlight=?, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: com.datastax.driver.core.exceptions.DriverInternalError: Unknown response opcode ??)
2017-11-11 19:03:30 +0100 401 [/??.???.??.??:????] Connection[/??.???.??.??:????-???, inFlight=?, closed=false] failed, remaining = ???
2017-11-11 19:03:33 +0100 1 Defuncting Connection[/??.???.??.??:????-???, inFlight=???, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: com.datastax.driver.core.exceptions.DriverInternalError: Unknown response opcode ???)
2017-11-11 19:03:41 +0100 722 Defuncting Connection[/??.???.??.??:????-???, inFlight=?, closed=false] because: [/??.???.??.??:????] Heartbeat query timed out
2017-11-11 19:03:41 +0100 8 [/??.???.??.??:????] Connection[/??.???.??.??:????-?, inFlight=?, closed=false] failed, remaining = ???
2017-11-11 19:03:41 +0100 11 Defuncting Connection[/??.???.??.??:????-?, inFlight=?, closed=false] because: [/??.???.??.??:????] Heartbeat query timed out
2017-11-11 19:03:41 +0100 67 [/??.???.??.??:????] Connection[/??.???.??.??:????-??, inFlight=?, closed=false] failed, remaining = ???
2017-11-11 19:03:41 +0100 115 Defuncting Connection[/??.???.??.??:????-??, inFlight=?, closed=false] because: [/??.???.??.??:????] Heartbeat query timed out
2017-11-11 19:03:44 +0100 2 Defuncting Connection[/??.???.??.??:????-???, inFlight=??, closed=false] because: [/??.???.??.??:????] Unexpected exception triggered (io.netty.handler.codec.DecoderException: com.datastax.driver.core.exceptions.DriverInternalError: Unknown response opcode ?)
2017-11-11 19:03:51 +0100 2 Defuncting Connection[/??.???.??.??:????-???, inFlight=???, closed=false] because: [/??.???.??.??:????] Heartbeat query timed out
2017-11-11 19:03:51 +0100 265 Failed to post timeseries data Error Returned -
2017-11-11 19:03:57 +0100 3 Defuncting Connection[/??.???.??.??:????-???, inFlight=??, closed=false] because: [/??.???.??.??:????] Heartbeat query timed out
2017-11-11 19:04:01 +0100 39 Defuncting Connection[/??.???.??.??:????-???, inFlight=?, closed=false] because: [/??.???.??.??:????] Operation timed out
2017-11-11 19:04:01 +0100 12 Error processing jobs: execution of statement failed:All host(s) tried for query failed (tried: /??.???.??.??:???? (com.datastax.driver.core.exceptions.DriverException: Timeout while trying to acquire available connection (you may want to increase the driver number of per-host connections)), /??.???.??.??:???? (com.datastax.driver.core.exceptions.DriverException: Timeout while trying to acquire available connection (you may want to increase the driver number of per-host connections)), /??.???.??.??:???? (com.datastax.driver.core.exceptions.DriverException: Timeout while trying to acquire available connection (you may want to increase the driver number of per-host connections)), /??.???.??.??:???? [only showing errors of first ? hosts, use getErrors() for more details])
有人知道根本原因是什么吗
# 1 楼答案
请检查应用程序使用的直接内存设置。确保有足够的内存可供驱动程序分配。卡桑德拉需要分配直接内存。在它无法分配内存的情况下，我已经看到了类似的问题，即它被报告为NoHostAvailableException，即使它与内存有关
# 2 楼答案
你有一些记忆问题。只要存在这些问题，就不能指望驱动程序正常工作。你还说你的应用程序在几个小时后停止工作。在我看来，应用程序中似乎存在内存泄漏