Postgres - testing database connection in bash
pg_isready
is a utility for checking the connection status of a PostgreSQL database server. The exit status specifies the result of the connection check.
It can easily be used in bash. PostgresSQL Docs - pg_isready
Example Usage:
pg_isready -d <db_name> -h <host_name> -p <port_number> -U <db_user>
Exit Status
pg_isready
returns the following to the shell:
0 - if the server is accepting connections normally, 1 - if the server is rejecting connections (for example during startup), 2 - if there was no response to the connection attempt, and 3 - if no attempt was made (for example due to invalid parameters).
Notice: man pg_isready
states: It is not necessary to supply correct user name, password, or database name values to obtain the server status; however, if incorrect values are provided, the server will log a failed connection attempt.
you can write a simple connection script in your language of choice.
hopefully your Core OS system has one of perl, php, python, ruby, etc installed
here is one in python:
#!/usr/bin/python2.4#import psycopg2try: db = psycopg2.connect("dbname='...' user='...' host='...' password='...'")except: exit(1)exit(0)
now your cmdline looks like this
python psqltest.py && echo 'OK' || echo 'FAIL'
You can build a simple container that extends the first (to conserve disk) to perform the check. For example:
FROM postgresENTRYPOINT [ "psql", "-h", "$POSTGRES_PORT_5432_TCP_ADDR", "-p", "$POSTGRES_PORT_5432_TCP_PORT" ]
If you're using a different image than postgres
, of course use that one. You can use pretty much any command line you like and still check exit codes from bash on the CoreOS host:
#!/bin/shif ! docker run --link postgres:postgres psql --command "select * from foo;" ; then # Do somethingfi