I'm running a Google Cloud SQL instance ("mysql-master") and it has one replica. ("mysql-replica") Web apps on another servers read and write data on the Cloud SQL instance.

While mysql-master is restarting, can app servers read and write data?

I want to run gcloud sql instances patch mysql-master, but it sometimes requires the instance to restart. I wonder if web apps can read/write data on the instance while it is restarting.


No, your read replica is a read-only, so it cannot take writes during downtime of the master. There's no good solutions to avoiding the downtime, but if you have a small database, it should come back in order seconds (most come back within 5 seconds or so).

  • 1
    Hmm... so you can read data while restarting, but cannot write, right? OK, thank you. – Jumpei Ogawa Nov 5 '15 at 4:12

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