Comment 0 for bug 622670

We use DBLoopTuner for all of our data model migration scripts. However, when a single slave in a replication set is being rebuilt, entire cluster lag skyrockets and any migration job we are doing stalls for ~12h or so (the time it takes to fully rebuild a slave).

While this is bad for migration scripts, it makes DBLoopTuner unusable for regular cronscripts. I've even have a case where it makes the script underperform when using DBLoopTuner: cronscripts/rosetta-pofile-stats-daily.py takes ages to finish even though it processes a relatively small number of rows (bug 622668).