A better wait-for-postgres.sh

wait-for-postgres.sh

#!/bin/bash -e
# wait-for-postgres.sh
# Adapted from https://docs.docker.com/compose/startup-order/

# Expects the necessary PG* variables.

until psql -c '\l'; do
  echo >&2 "$(date +%Y%m%dt%H%M%S) Postgres is unavailable - sleeping"
  sleep 1
done
echo >&2 "$(date +%Y%m%dt%H%M%S) Postgres is up - executing command"

exec ${@}

This example (as the original one in the docker website) is using the psql command. This command is not available in the "webapp" service though (only available in the "db" service). Am I getting something wrong?

You will need to install the "postgresql-client" package for these commands to be available in the webapp.

The included pg_isready command achieves the same as above without the retry limit.

See the complete config using this technique here.

A simplified Dockerfile is shown below. You will need to include a pgsql link for hostname in docker-compose.yml.

FROM openjdk:11

RUN apt-get update && apt-get install -y procps curl net-tools telnet
RUN apt-get install -y postgresql-client

#other things

COPY build/libs/app-0.0.1.war app.war

EXPOSE 8080

CMD until pg_isready --host=pgsql; do sleep 1; done \
    && java -jar app.war

For the above script replace the CMD with :

CMD wait-for-postgres.sh && java -jar app.war