[OSM-dev] Synchronous mode

[Paul Norman]

On 2/20/2018 12:07 PM, Darafei "Komяpa" Praliaskouski wrote:
> This suggests that currently apidb replicas aren't in synchronous 
> mode. Can it be switched to synchronous?
>
> https://www.postgresql.org/docs/9.5/static/warm-standby.html#SYNCHRONOUS-REPLICATION 
>

Given the absolutely miserable performance of waiting for the data to 
hit the disk on replicas, this is a bad idea and not normally 
recommended, although we could use remote_apply to reduce some of the 
problems.

The data loss potential is very minimal, particularly since anything 
that brings down the DB server is likely to cause much larger 
interruptions to mapping than the loss of 5 seconds of PostgreSQL 
replication.

It's also not an issue for an editor. The API provides a diff response, 
so the editor doesn't need to make another request.

In fact, this is the first API call I've seen where it is a potential 
issue, and we don't even know if it is one for sure. If MapRoulette is 
doing this as a batch process, it's probably easier to use the changeset 
diffs anyways.