Port Management
New
Introduced in 0.5.0, Enhanced in 0.6.0
proxy:ports <app> # List proxy port mappings for an app
proxy:ports-add <app> <scheme>:<host-port>:<container-port> [<scheme>:<host-port>:<container-port>...] # Add proxy port mappings to an app
proxy:ports-clear <app> # Clear all proxy port mappings for an app
proxy:ports-remove <app> <host-port> [<host-port>|<scheme>:<host-port>:<container-port>...] # Remove specific proxy port mappings from an app
proxy:ports-set <app> <scheme>:<host-port>:<container-port> [<scheme>:<host-port>:<container-port>...] # Set proxy port mappings for an 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
Warning
Mapping alternative ports may conflict with the active firewall installed on your server or hosting provider. Such software includes - but is not limited to - AWS Security Groups, iptables, and UFW. Please consult the documentation for those softwares as applicable.
New
Introduced in 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.
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-* commands detailed below.
Listing port mappings
To inspect the port mapping for a given application, use the proxy:ports command:
The above application is listening on the host's port 80, which we can test via curl:
Adding a custom port mapping
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:
However, we can use the proxy:ports-add command to add a second external port mapping - 8080 - to our application's port 5000.
We can now test that port 80 still responds properly:
And our new listening port of 8080 also works:
Setting all port mappings at once
Port mappings can also be force set using the proxy:ports-set command.
Removing a port mapping
A port mapping can be removed using the proxy:ports-remove command if it no longer necessary:
Ports may also be removed by specifying only the host-port value. This effectively acts as a wildcard and removes all mappings for that particular host port.
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
Info
Changed as of 0.5.0
Dokku's default proxy implementation - nginx - supports HTTP and GRPC 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:
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
PORTenvironment variable. - switch to using an
EXPOSEdirective 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.