Wait for the container service to start with docker healthcheck

Overview

If you specify the container dependency with depends_on of docker-compose, you can control the container startup order, but Is the launched container working properly? Because it does not guarantee until There are many troublesome cases such as "Please do your best on the application side such as wait-for-it to check whether the middleware container is started properly". https://docs.docker.jp/compose/startup-order.html

So, docker has a healthcheck function, https://dev.classmethod.jp/articles/docker-healthcheck/ The story is that using this will make you wait for the dependent container to start until it becomes healthy.

Try out

Try putting redis in alpine.

Dockerfile

FROM alpine:latest

RUN apk add make redis

Makefile

node1:    #The side to be kept waiting
	@ echo "$@ is running!"
	redis-cli -h node2 ping

node2:    #The side that makes you wait
	@ echo "$@ started!"
	sleep 3    #Wait 3 seconds
	redis-server --protected-mode no    # redis-start server
	@ echo "$@ ended!"

docker-compose.yml

version: '3'

services:
  node1:
    image: hoge
    build:
      context: .
    command: make -f /mnt/Makefile node1
    depends_on:
      node2:    #Wait for startup until node2 healthcheck passes
        condition: service_healthy
    volumes:
      - .:/mnt

  node2:
    image: hoge
    build:
      context: .
    command: make -f /mnt/Makefile node2
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 1s
      timeout: 30s
      retries: 30
    volumes:
      - .:/mnt

with this

bash

$ docker-compose build

do it

bash

$  docker-compose up

Then, while sleeping for 3 seconds before starting redis on node2 side, healthcheck redis-cli ping does not pass, so You can see the behavior of waiting for node1 to start.

Like this

$ docker-compose up
Creating network "docker_default" with the default driver
Creating docker_node2_1 ... done
Creating docker_node1_1 ... done
Attaching to docker_node2_1, docker_node1_1
node2_1  | node2 is started!
node2_1  | sleep 3    #Wait 3 seconds
node1_1  | node1 is running!
node1_1  | redis-cli -h node2 ping
node2_1  | redis-server --protected-mode no    # redis-start server
node2_1  | 22:C 22 Dec 2020 09:38:25.036 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
node2_1  | 22:C 22 Dec 2020 09:38:25.036 # Redis version=5.0.9, bits=64, commit=869dcbdc, modified=0, pid=22, just started
node2_1  | 22:C 22 Dec 2020 09:38:25.036 # Configuration loaded
node1_1  | PONG
node2_1  | 22:M 22 Dec 2020 09:38:25.039 * Running mode=standalone, port=6379.
node2_1  | 22:M 22 Dec 2020 09:38:25.039 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
node2_1  | 22:M 22 Dec 2020 09:38:25.039 # Server initialized
node2_1  | 22:M 22 Dec 2020 09:38:25.039 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
node2_1  | 22:M 22 Dec 2020 09:38:25.040 * Ready to accept connections
docker_node1_1 exited with code 0

The story.

cf.

https://til.codes/health-check-option-in-docker-to-wait-for-dependent-containers-to-be-healthy/