Wait for another service to become available

./wait-for is a script designed to synchronize services like docker containers. It is sh and alpine compatible. It was inspired by vishnubob/wait-for-it, but the core has been rewritten at Eficode by dsuni and mrako.

Usage

./wait-for host:port [-t timeout] [-- command args]
  -q | --quiet                        Do not output any status messages
  -t TIMEOUT | --timeout=timeout      Timeout in seconds, zero for no timeout
  -- COMMAND ARGS                     Execute command with args after the test finishes

To include that in the Dockerfile

# download wait-for script
RUN wget https://raw.githubusercontent.com/LukasForst/wait-for/master/wait-for
RUN chmod +x wait-for

It is better to use wget and not ADD as ADD downloads file every time.

Examples

To check if eficode.com is available:

$ ./wait-for www.eficode.com:80 -- echo "Eficode site is up"

Connection to www.eficode.com port 80 [tcp/http] succeeded!
Eficode site is up

To wait for database container to become available:

version: '2'

services:
  db:
    image: postgres:9.4

  backend:
    build: backend
    command: sh -c './wait-for db:5432 -- npm start'
    depends_on:
      - db

Note

Make sure netcat is installed in your Dockerfile before running the command.

RUN apt-get -q update && apt-get -qy install netcat

https://stackoverflow.com/questions/44663180/docker-why-does-wait-for-always-time-out