以我的经验，ZK超时几乎总是归因于Solr节点上的某些问题，而不是ZK中的问题.

In my experience, ZK timeouts have almost always been due to something on the Solr node, rather than a problem in ZK.

您未提供所有时间戳，但理论是:

You don't provide all the timestamps, but the theory is that:

1. Solr由于某种原因无法发送心跳
2. ZK假定客户端已离开并关闭连接
3. Solr尝试使用ZK关闭的连接

那么Solr节点为什么无法发送心跳?这可能是因为Solr节点只是过载(线程尖峰是原因，还是症状?)，或者只是经过很长的GC暂停也可以做到这一点.

So why might the Solr node fail to send the heartbeat? This could be because the Solr node was simply overloaded, (Is the thread spike a cause, or a symptom?) or just working through a very long GC pause could do it too.