Re: Support load balancing in libpq

Hi Jelte,

> Load balancing connections across multiple read replicas is a pretty
> common way of scaling out read queries. There are two main ways of doing
> so, both with their own advantages and disadvantages:
> 1. Load balancing at the client level
> 2. Load balancing by connecting to an intermediary load balancer
>
> Option 1 has been supported by JDBC (Java) for 8 years and Npgsql (C#)
> merged support about a year ago. This patch adds the same functionality
> to libpq. The way it's implemented is the same as the implementation of
> JDBC, and contains two levels of load balancing:
> 1. The given hosts are randomly shuffled, before resolving them
> one-by-one.
> 2. Once a host its addresses get resolved, those addresses are shuffled,
> before trying to connect to them one-by-one.

Thanks for the patch.

I don't mind the feature but I believe the name is misleading. Unless
I missed something, the patch merely allows choosing a random host
from the provided list. By load balancing people generally expect
something more elaborate - e.g. sending read-only queries to replicas
and read/write queries to the primary, or perhaps using weights
proportional to the server throughput/performance.

Randomization would be a better term for what the patch does.

--
Best regards,
Aleksander Alekseev