Don't you dare kill that process. Why ?
Run this query
SELECT COUNT(1) FROM information_schema.processlist WHERE user='system user';
The answer has to be two. Why ?
Standard MySQL Replication functions on 2 threads: 1) IO Thread, 2) SQL Thread. In my old post Does MySQL support replicating all databases?, I explain the symbiosis between the two threads.
When you run SHOW SLAVE STATUS\G, you will see three lines:
Slave_IO_Running: YesSlave_SQL_Running: YesSeconds_Behind_Master: 0
This is the sign of a healthy replication process.If either Slave_IO_Running or Slave_IO_Running is No, then Replication is not running for one of six(6)reasons:
- Somebody ran
STOP SLAVE;, which turns off both the IO Thread and SQL Thread
- Somebody ran
STOP SLAVE IO_THREAD;, which turns off the IO Thread
- Somebody ran
STOP SLAVE SQL_THREAD;, which turns off the SQL Thread
- There was a replication user authentication error, which turns off the IO Thread
- There was a network error, which turns off the IO Thread
- There was an SQL Error, which turns off the SQL Thread
When any of these cases show up, Seconds_Behind_Master is NULL.
What about the number 280000 ? That is simply the length of time (over 82 hours) that the IO Thread has been running. That's OK. It is not a ghost process. Replication requires an IO Thread to read binlog events from a Master's binary logs.
In conclusion, your IO Thread has been up for over 82 hours. Do not mess with replication.
Seconds_behind_master bouncing between 0 and some 'large' value?
I have seen that scenario for 16 years. I have never found the cause or cure. The problem usually goes away after a day or two.
Bottom line: Ignore it.
Best Answer
It means nothing, really. PostgreSQL has a number of replication features, as the relevant chapter in the manual details.
That article is apallingly wrong and outdated. Ignore it. "No referential integrity" in MySQL? Bah.
If you have an account on that site, please ask for it to be removed or fixed or whatever can be done. As it stands it's dangerously misleading and wrong, and has no place claiming to be current accurate information.