Swift Vapor 3 + PostgreSQL + Docker-Compose Correct configuration? - postgresql

Question

Currently building a package to test some devOps configurations with AWS. Building an application with Swift Vapor3, PostgreSQL 11, Docker. Given my github Repo the project builds/tests/runs just fine with vapor build vapor test vapor run given that you have a local installation of postgresql installed with a username: test, password: test
However my api is not connecting to my DB and am worried my configuration is wrong.
version: "3.5"
services:
api:
container_name: vapor_it_container
build:
context: .
dockerfile: web.Dockerfile
image: api:dev
networks:
- vapor-it
environment:
POSTGRES_PASSWORD: 'test'
POSTGRES_DB: 'test'
POSTGRES_USER: 'test'
POSTGRES_HOST: db
POSTGRES_PORT: 5432
ports:
- 8080:8080
volumes:
- .:/app
working_dir: /app
stdin_open: true
tty: true
entrypoint: bash
restart: always
depends_on:
- db
db:
container_name: postgres_container
image: postgres:11.2-alpine
restart: unless-stopped
networks:
- vapor-it
ports:
- 5432:5432
environment:
POSTGRES_USER: test
POSTGRES_PASSWORD: test
POSTGRES_HOST: db
POSTGRES_PORT: 5432
PGDATA: /var/lib/postgresql/data
volumes:
- database_data:/var/lib/postgresql/data
pgadmin:
container_name: pgadmin_container
image: dpage/pgadmin4
environment:
PGADMIN_DEFAULT_EMAIL: test#test.com
PGADMIN_DEFAULT_PASSWORD: admin
volumes:
- pgadmin:/root/.pgadmin
ports:
- "${PGADMIN_PORT:-5050}:80"
networks:
- vapor-it
restart: unless-stopped
networks:
vapor-it:
driver: bridge
volumes:
database_data:
pgadmin:
# driver: local
Also while reading the Docker postgres docs I came across this in the "Caveats" section.
If there is no database when postgres starts in a container, then postgres will create the default database for you. While this is the expected behavior of postgres, this means that it will not accept incoming connections during that time. This may cause issues when using automation tools, such as docker-compose, that start several containers simultaneously.postgres dockerhub
I have not made those changes because I am not sure how to go about making that file or how the configuration would look. Has anyone done something like this that has some experience with connecting to Postgresql and using vapor as a back end?

Answer 1

The theory is, a well-behaved container should be able to gracefully handle not having its dependencies running, because despite the best efforts of your container scheduler, containers may come and go. So if your app needs a DB, but at any given moment the DB is unavailable, it should respond rationally. For example, returning a 503 for an HTTP request, or trying again after a delay for a scheduled task.
That’s theory though, and not always applicable. In your situation, maybe you really do just need your Vapor app to wait for Postgres to come available, in which case you could use a wrapper script that polls your DB and only starts your main app after the DB is ready.
See this suggested wrapper script from the Docker docs:
#!/bin/sh
# wait-for-postgres.sh
set -e
host="$1"
shift
cmd="$#"
until PGPASSWORD=$POSTGRES_PASSWORD psql -h "$host" -U "postgres" -c '\q'; do
>&2 echo "Postgres is unavailable - sleeping"
sleep 1
done
>&2 echo "Postgres is up - executing command"
exec $cmd
command: ["./wait-for-postgres.sh", "db", "vapor-app", "run"]