How to configure postgres + pgbouncer to allow a large number of connections

I am involved in stress testing pgbouncer with 5000 connections. The goal of the test is to multiplex the connection using pgbouncer, i.e. 5000 client connections with a 500dB connection.

However, I am unable to reach the target of the active 500 connection mark.

My setup is pretty simple

(client suite using pgbench) -----> pgbouncer + psql

| ______ several boxes ______ || ______ 1 box _________ |

pgbouncer and postgres are present in the same field.

pgbouncer = 1 core (pending)

postgres = 15 cores (pending)

• machine configuration :

  16 cores

  ulimit -n 10000

• Postgres configuration :

  max_connections = 500

  shared_buffers = 1GB

  work_mem = 100kB

• Pgbouncer config :

  pool_mode = transaction

  server_lifetime = 6000

  server_idle_timeout = 2000

  server_connect_timeout = 30

  default_pool_size = 500

  pool_size = 500

  pkt_buf = 4096

  server_login_retry = 2

• client configuration (8 boxes of 8 cores):

  Each client box is simulated as a set for clients using pgbench For a box with 8 boxes, I have set 16 threads to run requests

  pgbench -h -p 6541 -c -j 16 -d -f pgbench_Script.sql -T 360 -U postgres test

  pgbench_Script.sql

  \ setrandom delta 0 100000 insert into t4.emplog values ​​(nextval ('t4.employeeSeq') ,: delta);

Active queries in postgres:

select count(*) from pg_stat_activity where state like 'active';
count
-------
40

      

        
        
        
      

    

My expectation is to have around 500 active database connections through the connection pool. Problem : I only see a few connections ~ 40 active connections

OBSERVATIONS: I see several postgres processes in an "idle" state even though pgbouncer serves all clients. Suggesting that pgbouncer can't do the best it can. However, I cannot point out what the exact bottle neck is.

Potential bottleneck:

client request: pgbench makes each thread the master of the set when connecting. how can I simulate a large set of active concurrent connections?

pgbouncer: is my pgbouncer config wrong?

postgres: is my postgres config unable to handle large connection?