[google-cloud-sql-discuss] Re: Can I drop the failover CloudSQL instance and re-create it?

Hi Fady,

Thanks a lot for replying.

I checked and the replica lag for my instance is set to 0 (zero). I suppose that means that failover is almost being kept instantaneously in sync with the main instance?

So, you are saying that keeping failover instance in-sync couldn't be the reason for the drop I am (almost religiously) seeing every 4-5 minutes in the performance of the queries (both read and write)?

1) Is there any ideas you have on how I may dig up further to figure what might be happening on the db instance at such regular intervals? Could there be some MySQL level compaction, etc triggering at these 4-5 minutes interval? How do I start digging up such an issue?

2) Since the pausing of failover is not possible, are there any huge downsides to deleting and re-creating the replica (apart from the fact that for the duration of experimentation, the instance will not have a failover backup)?

     * When the failover is re-introduced, how will it be re-constructed? Will it be gradual, or are we looking at a db-performance risk because it'll be working too hard to get the failover up again? Our db is not on the small side, so I am a little worried about the effort it'll need to put in to get a new failover up-to-date.

Cheers,

Roshan

On Tuesday, 1 May 2018 02:18:00 UTC+5:30, Fady (Google Cloud Platform) wrote:

Hello Roshan,

According to this document " To minimize performance impact on the master, while ensuring that changes are never lost, the replica logs the update events, and then performs the updates in order."  Therefore, I highly doubt that there is specific task that runs every 4- 5 minutes to keep both instances synced, but rather in seconds per order of each operation . You may verify that by checking the replication lag metrics (seconds behind master).  

As for stopping/pausing the failover replica, it is not currently possible. As you mentioned, you would have to delete it, and this would render your master not to be configured with high availability. If you choose to recreate the replica, you may check this guide for quick configurations. I hope this helps

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