This lets you create more complex topologies and specify custom network drivers and options. Instead of just using the default app network, you can specify your own networks with the top-level networks key. To learn about multi-host overlay networks. You can make use of the built-in overlay driver to enable multi-host communication.Ĭonsult the Swarm mode section, to see how to set upĪ Swarm cluster, and the Getting started with multi-host networking When deploying a Compose application on a Docker Engine with Swarm mode enabled, See the links reference for more information. links : - ' db:database' db : image : postgres In the following example, db is reachable from web at the hostnames db and database: They are not required to enable services to communicate - by default, any service can reach any other service at that service’s name. Links allow you to define extra aliases by which a service is reachable from another service. It is a container’s responsibility to detect this condition, look up the name again and reconnect. If any containers have connections open to the old container, they are closed. Running containers can look up that name and connect to the new address, but the old address stops working. If you make a configuration change to a service and run docker compose up to update it, the old container is removed and the new one joins the network under a different IP address but the same name. Postgres://db:5432, and from the host machine, the connection string would Within the web container, your connection string to db would look like The service is accessible outside the swarm as well. Networked service-to-serviceĬommunication uses the CONTAINER_PORT. In the above example, for db, the HOST_PORT is 8001 and the container port isĥ432 (postgres default). It is important to note the distinction between HOST_PORT and CONTAINER_PORT.

For example, web’sĪpplication code could connect to the URL postgres://db:5432 and start Get back the appropriate container’s IP address. In Compose file format 3.x, you can optionally set the attachable propertyĮach container can now look up the hostname web or db and This means that standaloneĬontainers can connect to overlay networks. Starting in Compose file format 2.1, overlay networks are always created asĪttachable, and this is not configurable. In v2.1+, overlay networks are always attachable

A container is created using db’s configuration.

A container is created using web’s configuration.

A network called myapp_default is created.

When you run docker compose up, the following happens:

How to find subnet magic number