Vfrdtyky

im trying to build a simple To do app with docker-compose having 3 Containers: One Flask Rest API with sqlalchemy and marshmallow, one PHP to call my Rest-Api and one MySQL Database. The error im getting is:

sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, 

"Can't connect to MySQL server on 'db' ([Errno 111] Connection refused)") 

(Background on this error at: http://sqlalche.me/e/e3q8)

And i cant call my rest api from my php container.
Here is the code with the important lines:

my docker-compose.yml:

version: '3.1' #compose version



services: 

flaskapi-service:

 build: 

  context: ./restapi #relative to docker-compose file directory

  dockerfile: DOCKERFILE

 volumes: 

  - ./restapi:/usr/src/app #mounting

 ports:

  - 5001:5001 #host:container

 depends_on:

  - db

 restart: on-failure



db:

 image: mysql:latest

 restart: always

 environment:

  MYSQL_USER: username

  MYSQL_PASSWORD: password

  MYSQL_DATABASE: todo

  MYSQL_ROOT_PASSWORD: password

 ports:

   - "3306:3306"



php-page:

 build:

  context: ./frontend

  dockerfile: DOCKERFILE

 volumes:

  - ./frontend:/var/www/html #mount

 ports: 

  - 5002:80 #host:container

 depends_on: 

  - flaskapi-service 

my rest-api:

from flask_sqlalchemy import SQLAlchemy

from flask_marshmallow import Marshmallow

import pymysql



app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = 

'mysql+pymysql://username:password@db:3306/todo'



#order matters: ORM before serialization tool

db = SQLAlchemy(app)

ma = Marshmallow(app)

how im calling the rest-api from php:

 <?php

    $date_time = date('Y-m-d H:i:s');

    $data = array(

        'description' => $_POST['description'],

        'deadline' => $_POST['deadline'],

        'createdAt' => $date_time,

        'finished' => 'false'

    );



    $encodedJSON = json_encode($data);



    //Initiate cURL-handle

    $ch = curl_init();



    curl_setopt_array($ch, array(

        CURLOPT_URL => 'http://flaskapi-service/todo',

        CURLOPT_POST => 1,

        CURLOPT_POSTFIELDS => $encodedJSON,

        CURLOPT_HTTPHEADER => array('Content-Type: application/json')

    ));



    $result = curl_exec($ch);

    echo $result;

    curl_close($ch);

    header('Location: index.php');

 ?>

Any help is appreciated and the correct answer marked as correct.

Instead of "@db" in your SQLALCHEMY_DATABASE_URI, you want the actual address at which you can find the db container from your server.

You can, for example, find out what your docker machine ip is using

$ docker-machine ip

And then replace that ip in your URI. e.g.

'mysql+pymysql://username:password@192.168.0.123:3306/todo'

They might even be on the same host if all containers and on the same machine, so give this a shot:

'mysql+pymysql://username:password@localhost:3306/todo'

You can find other ways to determine the IP address of your MySQL instance in this discussion.

I solved this by downgrading from latest MySQL Version image to 5.7:

mysql:5.7

I dont have any clue why this should work since the returned error must be something e.g a misconfiguration with my docker and its networking and shouldnt have nothing to do with mysql. Maybe this helps someone.

Edit: allways check if your Database container is up before trying to connect since docker compose ist starting all containers simultaneously.