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Any danger to a MySQL master if the slave replica is locked down for an extended period of time? I am using 5.6.xx.

This question states that it's "safe", but does not speak to degradation in performance.

Things like full replication queues preventing transaction commit is bad. (this happens in some NoSQL DB w.r.t. writes) So are slowed master transactions.

I plan on making a change to my replica schema (recollation) that will take upwards of an hour of table lockdown. When completed, I will promote it, and in this way (hopefully) make a live schema change. During this hour, no replication will occur, and whatever queue/journal system MySQL uses will surely grow.

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There is absolutely no impact to the master's operations whether there is active replication or not, except of course for the load created by the replication process itself.

To be 100% clear, the master's transactions do not depend on its replication and therefore will not perform differently.

The only two actual risks of stopping the replication process are..

  1. Increased load on the master when replication is restarted.
  2. Lack of replication during the slave's outage in case of a disaster on the master.
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  • I don't know if this question was before or after this other one but assuming it's related then only the SQL thread would be locked, so no impact on point 1 in that case. (+1)
    – Michael - sqlbot
    Jul 24, 2016 at 0:19
  • To answer Michael's question, this was my follow-on comment to the aforementioned question…only in question form (confused? :-) ). I guess being burned by similar NoSQL situations (slowdowns on the replica, but of course not locks) resulting in failure led me to feel it important to ask. Strangely, no one to date had before AFAIK.
    – Mark Gerolimatos
    Jul 24, 2016 at 10:09

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