I'm facing an issue where I'm unable to connect to a MySQL database that is running on my host machine from a Docker container which houses Nginx. The MySQL instance is configured to listen on localhost (127.0.0.1), and I need to find a way to access it from within the container. I understand that containers are isolated environments and have their own localhost. I'm looking for some insight into a viable method or workaround for establishing a connection to the host's MySQL instance from the Docker container. Here is my current MySQL configuration:


I've considered updating the bind-address to 0.0.0.0 to allow connections from any host, but for security reasons, I want to avoid this approach. Is there a way to securely connect from my Docker container to the MySQL service running on the localhost of the host without changing the bind-address setting to 0.0.0.0?

Connecting from the Docker container to the MySQL database on the host without modifying the MySQL bind-address can be accomplished using a network bridge. You would map a port on the host to the MySQL port, then connect to the host's port from your Docker container. The Docker network needs to be set up to allow for communication between the container and the host. Here's an example of how you can map the port using Docker's `-p` option when you run your container:


Remember, the above command assumes you have changed your MySQL config to bind to the Docker bridge network IP, which would replace the 127.0.0.1 setting.

It's not recommended to expose your MySQL directly by binding to 0.0.0.0 or even to the Docker bridge network IP if security is a concern. Instead, consider setting up a Docker network and use the special DNS name `host.docker.internal` which resolves to your host machine's internal IP address from the Docker containers. You can then use this DNS name in your database connection string within your Nginx configuration, like so:


This way, you maintain the secure bind-address as localhost on your MySQL configuration, but your Docker container will be able to resolve and connect to it.

Do note that `host.docker.internal` is not available on all Docker networks, specifically not on the default bridge network. You would need to create a custom network. Also, this feature may not be available on Linux; it's predominantly for Docker on Windows and MacOS. If you're using Linux, you may have to obtain the host's IP address in another manner, such as inspecting the network gateway from within the container.
To create a custom network and obtain the gateway IP, you could use something like the following:


In the last line, you are extracting the default gateway which, in this case, would be the host machine. Then you can use that IP to connect to your MySQL server as long as MySQL allows connections from this Docker-assigned IP address.