scripts/monitoring/check_postgresql_replication.sh

#!/bin/sh
# check postgresql (streaming) replication
# tested with postgresql 11.3 on FreeBSD 11.2
#
# pg_hba.conf access should be set to trust
# warning (-w) and critical (-c) thresholds can be set in seconds
# on a low trafic server don't hesitate to set them to a high value
 
args=`getopt hw:c: $*`
set -- $args

warning=600
critical=3600

while :; do
	case "$1" in
		-h) echo "Usage: $0 [-h] [-w <warning> (default: $warning)] [-c <critical> (default: $critical)]"
		    shift;
		    exit 2;
		    ;;
		-w) warning=$2
		    shift; shift;
		    ;;
		-c) critical=$2
		    shift; shift;
		    ;;
		--)
		    shift; break;
		    ;;
	esac
done

delay=`/usr/local/bin/psql -U postgres --pset expanded=yes -c "select now() - pg_last_xact_replay_timestamp() AS replication_delay;" | tail -2 | head -1 | cut -d '|' -f 2 | cut -d ' ' -f 2 | cut -d '.' -f 1 | awk -F: '{ print ($1 * 3600) + ($2 * 60) + $3 }'`

if [ $delay -gt $critical ]
then
  echo "CRITICAL: $delay seconds behind master"
  exit 2
elif [ $delay -gt $warning ]
then
  echo "WARNING: $delay seconds behind master"
  exit 1
else
  echo "OK: $delay seconds behind master"
  exit 0
fi