Re: WAL insert delay settings

On 2/13/19 4:31 PM, Stephen Frost wrote:
> Greetings,
> 
> * Peter Eisentraut (peter.eisentraut@2ndquadrant.com) wrote:
>> Bulk operations like CREATE INDEX, ALTER TABLE, or bulk loads can create
>> a lot of WAL.  A lot of WAL at once can cause delays in replication.
> 
> Agreed, though I think VACUUM should certainly be included in this.
> 

Won't these two throttling criteria interact in undesirable and/or
unpredictable way? With the regular vacuum throttling (based on
hit/miss/dirty) it's possible to compute rough read/write I/O limits.
But with the additional sleeps based on amount-of-WAL, we may sleep for
one of two reasons, so we may not reach either limit. No?

> I'm all for the idea though it seems like a different approach is needed
> based on the down-thread discussion.  Ultimately, having a way to have
> these activities happen without causing issues for replicas is a great
> idea and would definitely address a practical issue that a lot of people
> run into.
> 

+1


-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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