neutronsharc / enhanced-semi-sync-replication Goto Github PK

What steps will reproduce the problem?
1. Config more than one semi-sync slave
2. Monitor the avg_net_wait or avg_trx_wait

Thread 33 is trying to rotate to a new log and is holding 
mysql_bin_log::LOCK_log. It is
unable to proceed because there are pending prepared transactions.

Thread 32 (at least) has a prepared transaction. It is unable to progress 
beyond prepared
to committed because it needs an acknowledgment from a semi-sync slave.
It's not getting the acknowledgment from the slaves because the Binlog Dump 
threads are
blocked reading events because they can't lock LOCK_log which is held by thread 
33.



thread 1                        || thread 2                          
innodb prepare                  || innodb prepare                   1. lock 
LOCK_log
write binary log(xid_prepare++) || rotate binary first============> 2. waiting  
xid_prepare === 0   
...                             || write binary log(xid_prepare++)  3. 
...                             || wait slave reply
...                             || 
...                             ||                                           
wait slave reply                || 
...                             || 
...                             || 
commit                          || 
tc_unlog...(xid_prepare--)      || 

dump thread try to get LOCK_log(thread 2 is holding this and wait thread 1) 
send the log.

Ok thread 1 is waiting dump thread finish it's job, dump thread is waiting 
thread 2 releasing the lock, thread 2 is waiting for thread 1 
unlog(xid_prepare--).

[deleted issue]