Compose: Mysql2::Error: Can't connect to MySQL server on 'db' (111)

[kyledecot]

Hi All,

I'm not sure if this is the right repo to post this to but I figured I'd start here and perhaps someone can at least point me in the right direction. I have a docker-compose.test.yml file which creates two services (web and db). Here is said file:

version: '2'
services:
  db:
    container_name: "rfc_test_db"
    image: mysql
    environment:
      - MYSQL_ALLOW_EMPTY_PASSWORD=1
  web:
    container_name: "rfc_test_web"
    stdin_open: true
    tty: true
    environment:
      - RAILS_ENV=test
      - DATABASE_HOST=db
      - DATABASE=mysql
      - DATABASE_USERNAME=root
      - DATABASE_PASSWORD=
      - SECRET_KEY_BASE=3ad576ebf101d796769739f909b4a84d01a9f99852765d51008ec7d
    build: .
    volumes:
      - .:/rfc
    depends_on:
      - db

The problem that I'm running into is when I perform an up and then a run that attempts to connect to the db service I get the following error:

Mysql2::Error: Can't connect to MySQL server on 'db' (111)

What's odd is that if I run the up and then wait ~30 seconds and then run everything works as expected. It appears that my networking isn't getting linked up or something. Has anyone else run into this problem?

docker-compose version: docker-compose version 1.9.0-rc2, build a2da43b
docker version: Docker version 1.12.3, build 6b644ec, experimental

Doesn't Work

docker-compose -f docker-compose.test.yml -p rfc_test up --build --remove-orphans -d
# immediately after this completes call 
docker-compose -f docker-compose.test.yml -p rfc_test run --rm web rake db:schema:load
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
-- create_table("attachments", {:force=>:cascade})
rake aborted!
Mysql2::Error: Can't connect to MySQL server on 'db' (111)
...

Works

docker-compose -f docker-compose.test.yml -p rfc_test up --build --remove-orphans -d
# wait ~30 seconds
docker-compose -f docker-compose.test.yml -p rfc_test run --rm web rake db:schema:load
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
-- create_table("attachments", {:force=>:cascade})
   -> 0.1204s
...

[shin-]

MySQL needs time to start up, and there's a latency until it starts answering on the allocated port. This has nothing to do with docker - you need to implement some sort of retry mechanism into your workflow to account for it.

HTH !

[wilsonsilva]

According to docker compose docs:

You can use a tool such as wait-for-it, dockerize or sh-compatible wait-for. These are small wrapper scripts which you can include in your application’s image and will poll a given host and port until it’s accepting TCP connections.