replication - why mysql has thousands of binlog dump threads with nearly 100% io util -
mysql version: 5.6.35 os : linux 2.6.32 1 master, 3 slaves; gtid on; semi-sync on
desc: master hanging, statement "show master status" blocked. got infomation iostat command: util 100%, , 50,000+ rsec/s, 300 wsec/s.
after 1 dba tried kill connections, connections not declined. found processlist this: 2127 threads @ "killed" state; 1521 threads's command "binlog dump gtid" @ "init" state.
and found 1521 threads connected 3 slave, 507 threads each slave; replication switch async mode while network instability.
why there many dump threads on master?
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