go-postgres-pool

Init

docker volume create test-postgres

docker run -d -p 5432:5432 \
      -v test-postgres:/var/lib/postgresql/data \
      -e POSTGRES_USER=test \
      -e POSTGRES_DB=test \
      -e POSTGRES_PASSWORD=secret \
      --name test-postgres \
      --hostname test-postgres \
 postgres:alpine

PG cluster

./setup_pg_cluster.sh

pg master

select * from pg_stat_replication;
select * from pg_replication_slots;
SHOW transaction_read_only;

pg slave

SHOW transaction_read_only;

select * from pg_stat_wal_receiver;
SELECT pg_wal_replay_pause();
SELECT pg_wal_replay_resume();
select now() - pg_last_xact_replay_timestamp();

SELECT
  pg_is_in_recovery() AS is_slave,
  pg_last_wal_receive_lsn() AS receive,
  pg_last_wal_replay_lsn() AS replay,
  pg_last_wal_receive_lsn() = pg_last_wal_replay_lsn() AS synced,
  (
   EXTRACT(EPOCH FROM now()) -
   EXTRACT(EPOCH FROM pg_last_xact_replay_timestamp())
  )::int AS lag;

SELECT
    pid AS session_id,
    usename AS username,
    application_name,
    client_addr AS client_ip,
    state,
    state_change,
    query,
    backend_start
FROM
    pg_stat_activity
WHERE
    state IS NOT NULL;