Working day to day with Percona Remote DBA customers, we have been facing an issue from time to time when MySQL replication lag is flapping between 0 and XXXXX constantly – i.e. Seconds_Behind_Master is 0 for a few secs, then it’s like 6287 or 25341, again 0 and so on. I would like to note the 5 different scenarios and symptoms of this – some are obvious and some are not really. 1. Duplicate serve
![5 reasons why MySQL replication lag is flapping between 0 and XXXXX](https://cdn-ak-scissors.b.st-hatena.com/image/square/c490fa28a409e14eb7713edb97123c3fb4bff8f9/height=288;version=1;width=512/https%3A%2F%2Fwww.percona.com%2Fblog%2Fwp-content%2Fuploads%2F2013%2F08%2Fnagios-delay.png)