flink 1.11.0 chk超时

http://apache-flink.147419.n8.nabble.com/file/t538/QQ%E6%88%AA%E5%9B%BE20201105165123.jpg http://apache-flink.147419.n8.nabble.com/file/t538/QQ%E6%88%AA%E5%9B%BE20201105165200.jpg chk的历史如图，第三个subtask未能ack，同时在TM中只能找到如下信息：

2020-11-05 13:13:38,101 INFO org.apache.flink.streaming.api.functions.sink.filesystem.Buckets [] - Subtask 2 checkpointing for checkpoint with id=16 (max part counter=6). 2020-11-05 13:13:38,143 INFO org.apache.flink.streaming.api.functions.sink.filesystem.Buckets [] - Subtask 1 checkpointing for checkpoint with id=16 (max part counter=0). 2020-11-05 13:14:37,779 WARN org.apache.kafka.clients.NetworkClient [] - Connection to node -3 could not be established. Broker may not be available. 2020-11-05 13:14:37,786 WARN org.apache.kafka.clients.NetworkClient [] - Connection to node -2 could not be established. Broker may not be available. 2020-11-05 13:33:38,115 INFO org.apache.flink.runtime.taskmanager.Task [] - Attempting to cancel task Source: Custom Source -> Process -> (Sink: ***, Sink: *** sink, Sink: ***) (3/3) (68bfa6305a9aa5a7381b9ca4a8fef2fa).

请路过的大佬们指点下排查方式，多谢（当前日志级别暂无法改成debug）*来自志愿者整理的flink邮件归档