I have a Kong API Gateway container and a postgres container and I need to check whether postgres has started up and ready from the Kong container before running the migrations. I was thinking of installing the postgres client utilities into a custom image based on the official Kong image using RUN yum install postgresql -y && yum clean all in my Dockerfile and using either psql or pg_isready to achieve this. I've created a postgres user called polling with an empty password specifically for checking the status of the server by these two utilities. Neither of them work.
I tried to execute these commands from the custom Kong image:
psql. The command psql -h postgres -U polling -w -c '\l' fails with the error psql: fe_sendauth: no password supplied. But the user has no password. What am I doing wrong? The full shell script checking whether the server is ready using psql is described here.
pg_isready. I don't get how to install this utility separately into a custom image based on the official Kong image which in turn based on the centos:7 image, the postgresql package doesn't include pg_isready. Only these utilities are installed and can be found in /usr/bin: pg_config, pg_dump, pg_dumpall, pg_restore, psql. How to install pg_isready? I don't want to have the full server installation in the Kong image.
My solution was to create a new image based on the official kong image and override the entrypoint like this:
#!/usr/bin/env bash
set -e
# Disabling nginx daemon mode
export KONG_NGINX_DAEMON="off"
# Setting default prefix (override any existing variable)
export KONG_PREFIX="/usr/local/kong"
# Prepare Kong prefix
if [ "$1" = "/usr/local/openresty/nginx/sbin/nginx" ]; then
kong prepare -p "/usr/local/kong"
fi
#waiting for postgres
until psql --host=$KONG_PG_HOST --username=$POLLING_USER $POLLING_DATABASE -w &>/dev/null
do
echo "Waiting for PostgreSQL..."
sleep 1
done
echo "Postgres is ready, running the migrations..."
kong migrations up
echo "READY TO START UP KONG USING CMD" $@;
exec "$@"