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I'm currently trying to dockerize my app for local development. For a bit of context, it is using Magento.

I have a configuration file where I'm used to set 127.0.0.1 as MySQL hostname as the web app is running on the same host as MariaDB.

Initially, I've tried to link my container within my docker-compose file using 'links' (below an extract of my docker-compose setting at this point)

    mariadb:
      image: mariadb:5.5
    php-fpm:
      build: docker/php-fpm
      links:
        - "mariadb:mysql"

At this point, MariaDB was reachable by setting mysql as hostname in my configuration file instead of 127.0.0.1. However, I wanted to keep 127.0.0.1.

After a bit of digging, I've found this blog post where it is explained how to set up containers so that it can be reached through localhost or 127.0.0.1

This is working as I'm expecting but it has a flaw.

Without Docker, I'm able to run PHP scripts which leverage magento core modules by loading it. But with Docker and the blog post configuration, I'm not able to do it anymore as Magento is weirdly expecting for a DB hostname called "mysql".

Is there anyway through docker-compose to have a container be reachable with localhost and an hostname?

Without Docker, if I install MariaDB on my host machine, I am able to connect to its instance through 127.0.0.1:3306 or mysql://. I want to get a similar behaviour.

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    Obviously this is NOT a problem of docker, but of Magento... Commented Mar 11, 2020 at 11:24
  • I'm not so sure about this as it works without docker, if I install MariaDB on my machine directly. The scripts were working with the 'links' though, it stopped working with the namespace networks.. Commented Mar 11, 2020 at 11:26

2 Answers 2

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As said by @Sai Kumar you can connect the docker containers to the host network and then can use localhost to access services. But the problem is the port will be reserved by that container and will not be available till it is deleted.

But from your question, the following sentence caught my attention

Without Docker, I'm able to run PHP scripts which leverage magento core modules by loading it. But with Docker and the blog post configuration, I'm not able to do it anymore as Magento is weirdly expecting for a DB hostname called "mysql"

So If I understand properly Magento is expecting to connect to MySQL with mysql as hostname instead of localhost. If so this can be easily solved.

How?

So in docker, there is a concept called service discovery. I've explained the same in many of my answers. Basically what it does is it resolves IP of containers by container hostname/aliases.So, instead of connecting between containers using IP address you can connect between them by using their hostname such that even if container restarts(which results in change of IP), Docker will take care of resolving it to respective container.

This works only with user-defined networks. So what you can do is create a bridge network and connect both Magento and Mysql to it. and give the container_name as mysql for mysql or you can also use alias as mentioned here. So putting it all together a sample docker compose will be

version: '3'
services:
  mariadb:
    image: mariadb:5.5
    container_name: mysql #This can also be used but I always prefer using aliases
    networks:
      test:
        aliases:
          - mysql #Any container connected to test network can access this simply by using mysql as hostname   
  php-fpm:
    build: docker/php-fpm
    networks:
      test:
        aliases:
          - php-fpm
networks:
  test:
    external: true

More references
1. Networking in Compose.
2. Docker Networking.

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Yes you can connect through your db with localhost or 127.0.0.1 But this is only possible when you create docker-compose network in host mode. But when you set your docker network in host mode then containerising concept will fail. So you have to choose host or bridge network mode

You can find networking in docker-compose

network_mode: "host"
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1 Comment

And don't add any links in your docker-compose when you add links with network mode it will failed

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