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Port Management

New as of 0.5.0, Enhanced in 0.6.0

proxy:ports <app>                        # List proxy port mappings for app
proxy:ports-add <app> <scheme>:<host-port>:<container-port> [<scheme>:<host-port>:<container-port>...]           # Set proxy port mappings for app
proxy:ports-clear <app>                  # Clear all proxy port mappings for app
proxy:ports-remove <app> <host-port> [<host-port>|<scheme>:<host-port>:<container-port>...]                      # Unset proxy port mappings for app

In Dokku 0.5.0, port proxying was decoupled from the nginx-vhosts plugin into the proxy plugin. Dokku 0.6.0 introduced the ability to map host ports to specific container ports. In the future this will allow other proxy software - such as HAProxy or Caddy - to be used in place of nginx.

Usage

Proxy port mapping

New as of 0.6.0

You can now configure host -> container port mappings with the proxy:ports-* commands. This mapping is currently supported by the built-in nginx-vhosts plugin.

To inspect the port mapping for a given application, use the proxy:ports command:

dokku proxy:ports node-js-app
-----> Port mappings for node-js-app
-----> scheme             host port                 container port
http                      80                        5000

The above application is listening on the host's port 80, which we can test via curl:

curl http://node-js-app.dokku.me
Hello World!

There are cases where we may wish for the service to be listening on more than one port, such as port 8080. Normally, this would not be possible:

curl http://node-js-app.dokku.me:8080
curl: (7) Failed to connect to node-js-app.dokku.me port 8080: Connection refused

However, we can use the proxy:ports-add command to add a second external port mapping - 8080 - to our application's port 5000.

dokku proxy:ports-add node-js-app http:8080:5000
-----> Setting config vars
       DOKKU_PROXY_PORT_MAP: http:80:5000 http:8080:5000
-----> Configuring node-js-app.dokku.me...(using built-in template)
-----> Creating http nginx.conf
-----> Running nginx-pre-reload
       Reloading nginx

We can now test that port 80 still responds properly:

curl http://node-js-app.dokku.me
Hello World!

And our new listening port of 8080 also works:

curl http://node-js-app.dokku.me:8080
Hello World!

You can also remove a port mapping that is no longer necessary:

dokku proxy:ports-remove node-js-app http:80:5000

By default, buildpack apps and dockerfile apps without explicitly exposed ports (i.e. using the EXPOSE directive) will be configured with a listener on port 80 (and additionally a listener on 443 if ssl is enabled) that will proxy to the application container on port 5000. Dockerfile apps with explicitly exposed ports will be configured with a listener on each exposed port and will proxy to that same port of the deployed application container.

Note: This default behavior will not be automatically changed on subsequent pushes and must be manipulated with the proxy:ports-* syntax detailed above.

Port management by Deployment Method

WARNING: If you set a proxy port map but do not have a global domain set, Dokku will reset that map upon first deployment.

Buildpacks

For buildpack deployments, your application must respect the PORT environment variable. We will typically set this to port 5000, but this is not guaranteed. If you do not respect the PORT environment variable, your containers may start but your services will not be accessible outside of that container.

Dockerfile

Changed as of 0.5.0

Dokku's default proxy implementation - nginx - only supports HTTP request proxying. At this time, we do not support proxying plain TCP or UDP ports. UDP ports can be exposed by disabling the nginx proxy with dokku proxy:disable myapp. If you would like to investigate alternative proxy methods, please refer to our proxy management documentation.

Applications using EXPOSE

Dokku will extract all tcp ports exposed using the EXPOSE directive (one port per line) and setup nginx to proxy the same port numbers to listen publicly. If you would like to change the exposed port, you should do so within your Dockerfile.

For example, if the Dokku installation is configured with the domain dokku.me and an application named node-js-app is deployed with following Dockerfile:

FROM ubuntu:14.04
EXPOSE 1234
RUN python -m SimpleHTTPServer 1234

The application would be exposed to the user at node-js-app.dokku.me:1234. If this is not desired, the following application configuration may be applied:

# add a port mapping to port 80
dokku proxy:ports-add node-js-app http:80:1234

# remove the incorrect port mapping
dokku proxy:ports-remove node-js-app http:1234:1234

Applications not using EXPOSE

Any application that does not use an EXPOSE directive will result in Dokku defaulting to port 5000. This behavior mimics the behavior of a Buildpack deploy. If your application does not support the PORT environment variable, then you will either need to:

  • modify your application to support the PORT environment variable.
  • switch to using an EXPOSE directive in your Dockerfile.

Switching between EXPOSE usage modes

When switching between EXPOSE usage modes, it is important to reset your port management. The following two commands can be used to reset your state and redeploy your application.

# assuming your application is called `node-js-app`
dokku config:unset --no-restart node-js-app DOKKU_DOCKERFILE_PORTS PORT
dokku proxy:ports-clear node-js-app

Docker Image

When deploying an image, we will use docker inspect to extract the ExposedPorts configuration and if defined, use that to populate port mapping. If this behavior is not desired, you can override that configuration variable with the following commands.

# assuming your application is called `node-js-app`
dokku config:set node-js-app DOKKU_DOCKERFILE_PORTS="1234/tcp 80/tcp"
dokku proxy:ports-clear node-js-app

All other port-related behavior is the same as when deploying via Dockerfile.

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