PostgreSQL 12 High Availability Cookbook - Third Edition

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We've mentioned adjusting pool size several times in this recipe. Since Pgpool acts as a single proxy for several database and user combinations, we can actually override the default in cases where pools require more direct management. For instance, suppose we change our entry in /etc/pgbouncer/pgbouncer.ini for the postgres database to this:

postgres = host=pgha1 pool_size=5 

Then, no user connecting to the postgres database can use more than five connections, even if the default is 50 per pool. Keep this in mind when analyzing the pools, clients, servers, and other statistics that PgBouncer collects on our behalf. We will most likely need several adjustments before reaching an ideal state that won't overwhelm the PostgreSQL ...