Waiting for a Docker container to be ready

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I have the following docker-compose.yml:

version: '2'
services:
  server:
    build: .
    command: ["./setup/wait-for-postgres.sh", "tide_server::5432", "cd /app", "npm install", "npm run start"]
    ports:
      - 3030:3030
    links:
      - database
    depends_on:
      - database
  database:
    image: postgres
    environment:
      - "POSTGRES_USER=postgres"
      - "POSTGRES_PASSWORD=postgres"
      - "POSTGRES_DB=tide_server"
    ports:
      - 5432:5432

I tried following this tutorial and using the following shell script to determine when postgres is ready.

#!/bin/bash
# wait-for-postgres.sh

set -e

host="$1"
shift
cmd="$@"

until psql -h "$host" -U "postgres" -c '\l'; do
  >&2 echo "Postgres is unavailable - sleeping"
  sleep 1
done

>&2 echo "Postgres is up - executing command"
exec $cmd

My node Dockerfile is minimal but I have added it for reference:

FROM node:latest

ADD . /app

WORKDIR /app

EXPOSE 3030

Now when I try to run docker-compose up I get the following (after the postgres container is ready:

server_1    | Postgres is unavailable - sleeping
server_1    | ./setup/wait-for-postgres.sh: line 10: psql: command not found
server_1    | Postgres is unavailable - sleeping
server_1    | ./setup/wait-for-postgres.sh: line 10: psql: command not found
server_1    | Postgres is unavailable - sleeping
server_1    | ./setup/wait-for-postgres.sh: line 10: psql: command not found
server_1    | Postgres is unavailable - sleeping
server_1    | ./setup/wait-for-postgres.sh: line 10: psql: command not found

Now I am not sure if this is a linking issue, or something wrong with my script but I have tried every variation I can think of and have had no luck getting this up/

dockerfile docker-compose docker linker-errors postgresql
2 Answers

This will successfully wait for Postgres to start. (Specifically line 6)

services:
  practice_docker: 
    image: dockerhubusername/practice_docker
    ports: 
      - 80:3000
    command: bash -c 'while !</dev/tcp/db/5432; do sleep 1; done; npm start'
    depends_on:
      - db
    environment:
      - DATABASE_URL=postgres://postgres:password@db:5432/practicedocker
      - PORT=3000   
  db:
    image: postgres
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=password
      - POSTGRES_DB=practicedocker
user_14325090
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