PostgreSQL HA tweaks

Lower timeout threshold

Machine: monitor

We want to lower the database timeout value, i.e. when the failover should be performed if the primary database is unreachable:

psql -p [port] -d pg_auto_failover
# List the health_check variables
SELECT name, setting FROM pg_settings WHERE name ~ 'pgautofailover\.health';
# Check status of database every 5s, setthe timeout to 2s and set the node unhealthy timeout to 5s
ALTER SYSTEM SET pgautofailover.health_check_period TO 5000;
ALTER SYSTEM SET pgautofailover.health_check_timeout TO 2000;
ALTER SYSTEM SET pgautofailover.node_considered_unhealthy_timeout TO 5000;
# Reload config:
select pg_reload_conf();
# Verify changes
SELECT name, setting FROM pg_settings WHERE name ~ 'pgautofailover\.health';
SELECT name, setting FROM pg_settings WHERE name ~ 'pgautofailover\.node';

Create a startup service

For each machine create a startup service that runs the pg_autoctl process:

Machine: monitor

pg_autoctl -q show systemd --pgdata /var/lib/pgsql/[monitor]/ | sudo tee /etc/systemd/system/pgautofailover.service
systemctl enable pgautofailover.service

Machine: node-1

pg_autoctl -q show systemd --pgdata /var/lib/pgsql/[node-1]/ | sudo tee /etc/systemd/system/pgautofailover.service
systemctl enable pgautofailover.service

Machine: node-2

pg_autoctl -q show systemd --pgdata /var/lib/pgsql/[node-2]/ | sudo tee /etc/systemd/system/pgautofailover.service
systemctl enable pgautofailover.service

Configuring PostgreSQL logging

Machine: monitor

sudo su - postgres
export PATH="$PATH:/usr/pgsql-12/bin"
psql -p [port]
ALTER SYSTEM SET log_truncate_on_rotation = 'on';
ALTER SYSTEM SET log_filename = 'postgresql-%a.log';
ALTER SYSTEM SET log_rotation_age = '1440';
ALTER SYSTEM SET log_line_prefix = '%m - %l - %p - %h - %[email protected]%d - %x';
ALTER SYSTEM SET log_directory = 'pg_log';
ALTER SYSTEM SET log_min_messages = 'WARNING';
ALTER SYSTEM SET log_min_error_statement = 'NOTICE';
ALTER SYSTEM SET log_min_duration_statement = '10s';
ALTER SYSTEM SET log_checkpoints = 'on';
ALTER SYSTEM SET log_lock_waits = 'on';
ALTER SYSTEM SET log_temp_files = '0';
ALTER SYSTEM SET log_connections=on;
ALTER SYSTEM SET log_disconnections=on;
ALTER SYSTEM SET log_duration=on;
SELECT pg_reload_conf();

Machine: node-1

sudo su - postgres
export PATH="$PATH:/usr/pgsql-12/bin"
psql -p [port]
ALTER SYSTEM SET log_truncate_on_rotation = 'on';
ALTER SYSTEM SET log_filename = 'postgresql-%a.log';
ALTER SYSTEM SET log_rotation_age = '1440';
ALTER SYSTEM SET log_line_prefix = '%m - %l - %p - %h - %[email protected]%d - %x';
ALTER SYSTEM SET log_directory = 'pg_log';
ALTER SYSTEM SET log_min_messages = 'WARNING';
ALTER SYSTEM SET log_min_error_statement = 'NOTICE';
ALTER SYSTEM SET log_min_duration_statement = '10s';
ALTER SYSTEM SET log_checkpoints = 'on';
ALTER SYSTEM SET log_lock_waits = 'on';
ALTER SYSTEM SET log_temp_files = '0';
ALTER SYSTEM SET log_connections=on;
ALTER SYSTEM SET log_disconnections=on;
ALTER SYSTEM SET log_duration=on;
SELECT pg_reload_conf();

Machine: node-2

sudo su - postgres
export PATH="$PATH:/usr/pgsql-12/bin"
psql -p [port]
ALTER SYSTEM SET log_truncate_on_rotation = 'on';
ALTER SYSTEM SET log_filename = 'postgresql-%a.log';
ALTER SYSTEM SET log_rotation_age = '1440';
ALTER SYSTEM SET log_line_prefix = '%m - %l - %p - %h - %[email protected]%d - %x';
ALTER SYSTEM SET log_directory = 'pg_log';
ALTER SYSTEM SET log_min_messages = 'WARNING';
ALTER SYSTEM SET log_min_error_statement = 'NOTICE';
ALTER SYSTEM SET log_min_duration_statement = '10s';
ALTER SYSTEM SET log_checkpoints = 'on';
ALTER SYSTEM SET log_lock_waits = 'on';
ALTER SYSTEM SET log_temp_files = '0';
ALTER SYSTEM SET log_connections=on;
ALTER SYSTEM SET log_disconnections=on;
ALTER SYSTEM SET log_duration=on;
SELECT pg_reload_conf();