Docker Compose Wait for Dependencies

Home Docker Compose Wait for Dependencies Docker Compose Wait for Postgres Container to be Ready

Docker Compose Wait for Postgres Container to be Ready

3 mins

Docker Compose Wait for Dependencies

666246717351584446  
517
Shares

This article provides an example for making docker-compose wait for Postgres or Postgresql container to be ready before starting a dependent docker application container. We’ll use the docker-compose-wait tool tool, which is a small command line utility allowing to wait for a fixed amount of seconds and/or to wait until a TCP port is open on a target image.

You need to add the docker-compose-wait tool in your application Dockerfile.



Contents:

Quick start

# Download a template
git clone https://github.com/kassambara/docker-compose-wait-for-container.git

# Build the demo application
cd docker-compose-wait-for-container/ex01-using-wait-tool
docker-compose build
# Running your app
docker-compose run my_super_app

# Stopping containers and cleaning
docker-compose down

Step 0: Download a template

# Download a template
git clone https://github.com/kassambara/docker-compose-wait-for-container.git
cd docker-compose-wait-for-container/ex02-using-wait-tool

Project folder structure:

files/docker-compose-wait-for-container/ex01-using-wait-tool
├── docker-compose.yml
└── my_super_app
    ├── Dockerfile
    └── sayhello

Essential project contents:

  • docker-compose.yml to run all container services
  • my_super_app scripts: template Dockerfile to build your application. Here, this demo app will ask your name and then congratulate you!

Step 1: Add the docker-compose-wait tool to your application Dockerfile

Example of Dockerfile using the alpine image:

FROM alpine:latest

# Add hello scripts
ADD sayhello /sayhello
RUN chmod +x /sayhello

# Add docker-compose-wait tool -------------------
ENV WAIT_VERSION 2.7.2
ADD https://github.com/ufoscout/docker-compose-wait/releases/download/$WAIT_VERSION/wait /wait
RUN chmod +x /wait

CMD ["/sayhello"]

Step 2: Modify your docker-compose.yml file

version: '3.6'
services:
  postgres:
    image: "postgres:9.4"
    hostname: postgres
    ports:
      - "5432:5432"

  my_super_app:
    build: ./my_super_app
    image: "my_super_app:latest"
    container_name: my_supper_app
    depends_on:
      - postgres
    command: sh -c "/wait && /sayhello"
    environment:
      - WAIT_HOSTS=postgres:5432
      - WAIT_HOSTS_TIMEOUT=300
      - WAIT_SLEEP_INTERVAL=30
      - WAIT_HOST_CONNECT_TIMEOUT=30
  • The command sh -c “/wait && /sayhello” will run the wait tool and then your application, here /sayhello.
  • To make your docker application container wait for multiple hosts, the environment variable can be specified as for example WAIT_HOSTS=postgres:5432, nginx:80

Additional configuration options. The behavior of the wait utility can be configured with the following environment variables:

  • WAIT_HOSTS: comma separated list of pairs host:port for which you want to wait.
  • WAIT_HOSTS_TIMEOUT: max number of seconds to wait for all the hosts to be available before failure. The default is 30 seconds.
  • WAIT_HOST_CONNECT_TIMEOUT: The timeout of a single TCP connection to a remote host before attempting a new connection. The default is 5 seconds.
  • WAIT_BEFORE_HOSTS: number of seconds to wait (sleep) before start checking for the hosts availability
  • WAIT_AFTER_HOSTS: number of seconds to wait (sleep) once all the hosts are available
  • WAIT_SLEEP_INTERVAL: number of seconds to sleep between retries. The default is 1 second.

Step 3: Building and running your app

# Building your app
cd docker-compose-wait-for-container/ex01-using-wait-tool
docker-compose build
# Running your app
docker-compose run my_super_app

Console log output looks like this (MySQL example):

Docker compose wait logs

After typing your name, you will see a congratulation message from my_super_app

Step 4: Stopping containers and cleaning

docker-compose down

Summary

This article describes how to make docker-compose wait for Postgres or Postgresql container using the docker-compose-wait tool.



 
          

Version: Français

Docker Compose Wait for MongoDB Container to be Ready (Prev Lesson)
(Next Lesson) Docker Compose Wait for Redis Container to be Ready
Back to Docker Compose Wait for Dependencies

Comments ( 2 )

Give a comment

Want to post an issue with R? If yes, please make sure you have read this: How to Include Reproducible R Script Examples in Datanovia Comments

Course Curriculum

Teacher
Alboukadel Kassambara
Role : Founder of Datanovia
Read More