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收到告警，从库有延时，登录上去看下没有什么慢查询，出现了下面的事件：
Slave_SQL_Running_State: Waiting for Slave Workers to free pending events
官方文档解释
This waiting action occurs when the total size of events being processed by Workers exceeds the size of the slave_pending_jobs_size_max system variable. The Coordinator resumes scheduling when the size drops below this limit. This state occurs only when slave_parallel_workers is set greater than 0.
临时将并行复制关闭