“Can't connect to local MySQL server” in docke

Question

I have Laravel application with MySQL and I'm trying to run it in Docker using docker-compose. But when app trying to connect DB, it throws:

PDOException in Connector.php line 55: SQLSTATE[HY000] [2002] Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

My docker-compose.yml:

load_balancer:
image: tutum/haproxy
links:
    - web
ports:
    - "80:80"

cache:
    image: redis

db:
    image: mysql
    environment:
        MYSQL_ROOT_PASSWORD: Q1w2e3r4t5
        MYSQL_DATABASE: regappbase

web:
    image: andrewmclagan/nginx-hhvm
    links:
        - db
        - cache
    volumes: 
        - ./:/var/www
    environment:
        - APP_ENV=local
        - DB_DATABASE=regappbase
        - DB_PASSWORD=Q1w2e3r4t5
        - VIRTUAL_HOST=laravel.local

My .env:

APP_ENV=production
APP_DEBUG=true
APP_KEY=SomeRandomString
APP_URL=http://laravel.local

DB_CONNECTION=mysql
DB_HOST=localhost
DB_PORT=3306
DB_DATABASE=regappbase
DB_USERNAME=root
DB_PASSWORD=Q1w2e3r4t5

CACHE_DRIVER=file
SESSION_DRIVER=file
QUEUE_DRIVER=sync

REDIS_HOST=laravel.local
REDIS_PASSWORD=null
REDIS_PORT=6379

MAIL_DRIVER=smtp
MAIL_HOST=mailtrap.io
MAIL_PORT=2525

Answer 1

Mysql connections to "localhost" by default attempt to connect over a socket present on the local machine. Your DB_HOST should be the linked container name, "db".

From the MYSQL docs:

On Unix, MySQL programs treat the host name localhost specially, in a way that is likely different from what you expect compared to other network-based programs. For connections to localhost, MySQL programs attempt to connect to the local server by using a Unix socket file. This occurs even if a --port or -P option is given to specify a port number. To ensure that the client makes a TCP/IP connection to the local server, use --host or -h to specify a host name value of 127.0.0.1, or the IP address or name of the local server. You can also specify the connection protocol explicitly, even for localhost, by using the --protocol=TCP option. For example:

Answer 2

You can change DB_HOST localhost to ip in .env. To receive ip mysql docker container need write command:

docker exec -it <CONTAINER_ID> ip add show eth0