Network Management¶
New
Introduced in 0.11.0, Enhanced in 0.20.0
network:create <network> # Creates an attachable docker network
network:destroy <network> # Destroys a docker network
network:exists <network> # Checks if a docker network exists
network:info <network> # Outputs information about a docker network
network:list # Lists all docker networks
network:report [<app>] [<flag>] # Displays a network report for one or more apps
network:rebuild <app> # Rebuilds network settings for an app
network:rebuildall # Rebuild network settings for all apps
network:set <app> <key> (<value>) # Set or clear a network property for an app
The Network plugin allows developers to abstract the concept of container network management, allowing developers to both change what networks a given container is attached to as well as rebuild the configuration on the fly.
Usage¶
Listing networks¶
New
Introduced in 0.20.0, Requires Docker 1.21+
You can easily list all available networks using the network:list command:
Note that you can easily hide extra output from Dokku commands by using the --quiet flag, which makes it easier to parse on the command line.
Creating a network¶
New
Introduced in 0.20.0, Requires Docker 1.21+
Docker networks can be created via the network:create command. Executing this command will create an attachable bridge network. This can be used to route requests between containers without going through any public network.
Specifying other additional flags or other types of networks can be created directly via the docker command.
Destroying a network¶
New
Introduced in 0.20.0, Requires Docker 1.21+
A Docker network without any associated containers may be destroyed via the network:destroy command. Docker will refuse to destroy networks that have containers attached.
Info
test
As the command is destructive, it will default to asking for confirmation before executing the removal of the network. This may be avoided by providing the --force flag:
Checking if a network exists¶
New
Introduced in 0.20.0, Requires Docker 1.21+
For CI/CD pipelines, it may be useful to see if an network exists before creating a new network. You can do so via the network:exists command:
The network:exists command will return non-zero if the network does not exist, and zero if it does.
Checking network info¶
New
Introduced in 0.20.0, Requires Docker 1.21+
Network information can be retrieved via the network:info command. This is a slightly different version of the docker network command.
Routing an app to a known ip:port combination¶
In some cases, it may be necessary to route an app to an existing $IP:$PORT combination. This is particularly the case for internal admin tools or services that aren't run by Dokku but have a web ui that would benefit from being exposed by Dokku. This can be done by using a proxy application and routing requests through that.
# for a service listening on:
# - ip address: 127.0.0.1
# - port: 8080
# create the app
dokku apps:create local-app
# add an extra host that maps host.docker.internal to the docker gateway
dokku docker-options:add local-app deploy "--add-host=host.docker.internal:host-gateway"
# set the SERVICE_HOST to the mapped hostname
dokku config:set local-app SERVICE_HOST=host.docker.internal
# set the SERVICE_PORT to the port combination for your app
dokku config:set local-app SERVICE_PORT=8080
# set the domains desired
dokku domains:set local-app local-app.dokku.me
# deploy the service-proxy image
dokku git:from-image local-app dokku/service-proxy:latest
Only a single $IP:$PORT combination can be routed to for a given app, and that $IP:$PORT combination must be accessible to the service proxy on initial deploy, or the service proxy won't start.
Attaching an app to a network¶
New
Introduced in 0.20.0, Requires Docker 1.21+
Apps will default to being associated with the default bridge network or a network specified by the initial-network network property. Additionally, an app can be attached to attachable networks by changing the attach-post-create or attach-post-deploy network properties when using the docker-local scheduler. A change in these values will require an app deploy or rebuild.
# associates the network after a container is created but before it is started
# commonly used for cross-app networking
dokku network:set node-js-app attach-post-create test-network
# associates the network after the deploy is successful but before the proxy is updated
# used for cross-app networking when healthchecks must be invoked first
dokku network:set node-js-app attach-post-deploy other-test-network
# associates the network at container creation
# typically blocks access to services and external routing
dokku network:set node-js-app initial-network global-network
Multiple networks can also be specified for the attach-post-create and attach-post-deploy phases.
# one or more networks can be specified
dokku network:set node-js-app attach-post-create test-network test-network-2
Setting the attach network property to an empty value will de-associate the container with the network.
dokku network:set node-js-app attach-post-create
dokku network:set node-js-app attach-post-deploy
dokku network:set node-js-app initial-network
The network properties can also be set globally. The global default value is an empty string, and the global value is used when no app-specific value is set.
dokku network:set --global attach-post-create global-create-network
dokku network:set --global attach-post-deploy global-deploy-network
dokku network:set --global initial-network global-network
The default value may be set by passing an empty value for the option.
dokku network:set --global attach-post-create
dokku network:set --global attach-post-deploy
dokku network:set --global initial-network
Network Aliases¶
Note
This feature is only available when an app has been attached to a network other than the default bridge network.
When a container created for a deployment is being attached to a network - regardless of which network property was used - a network alias of the pattern APP.PROC_TYPE will be added to all containers. This can be used to load-balance requests between containers. For an application named node-js-app with a process type of web, the network alias - or resolvable DNS record within the network - will be:
The fully-qualified URL for the resource will depend upon the PORT being listened to by the application. Applications built via buildpacks will have their PORT environment variable set to 5000, and as such internal network requests for the above example should point to the following:
Dockerfile-based applications may listen on other ports. For more information on how ports are specified for applications, please refer to the port management documentation.
Specifying a custom TLD¶
When attaching applications to networks, a custom TLD can be specified via the network:set command. This TLD is suffixed to the network alias for the application/process-type combination for all networks to which the application is attached, and cannot be customized per network. The default value is an empty string.
To specify a TLD of svc.cluster.local for your application, run the following command:
# replace node-js-app with your application name
dokku network:set node-js-app tld svc.cluster.local
With an application named node-js-app and a process-type named web, the above command will turn the network alias into:
Note that this has no impact on container port handling, and users must still specify the container port when making internal network requests.
The default value may be set by passing an empty value for the option:
The tld property can also be set globally. The global default is emty string, and the global value is used when no app-specific value is set.
The default value may be set by passing an empty value for the option.
When to attach containers to a network¶
Containers can be attached to a network for a variety of reasons:
- A background process in one app needs to communicate to a webservice in another app
- An app needs to talk to a container not managed by Dokku in a secure manner
- A custom network that allows transparent access to another host exists and is necessary for an app to run
Whatever the reason, the semantics of the two network hooks are important and are outlined before.
attach-post-create:- Phase it applies to:
build: Intermediate containers created during the build process.deploy: Deployed app containers.run: Containers created by theruncommand.
- Container state on attach:
createdbut notrunning - Use case: When the container needs to access a resource on the network.
- Example: The app needs to talk to a database on the same network when it first boots.
- Phase it applies to:
attach-post-deploy- Phase it applies to:
deploy: Deployed app containers.
- Container state on attach:
running - Use case: When another container on the network needs to access this container.
- Example: A background process needs to communicate with the web process exposed by this container.
- Phase it applies to:
initial-network:- Phase it applies to:
build: Intermediate containers created during the build process.deploy: Deployed app containers.run: Containers created by theruncommand.
- Container state on attach:
created - Use case: When another container on the network is already running and needed by this container.
- Example: A key-value store exposing itself to all your apps may be on the
initial-network.
- Phase it applies to:
Warning
If the attachment fails during the running container state, this may result in your application failing to respond to proxied requests once older containers are removed.
Rebuilding network settings¶
There are cases where you may need to rebuild the network configuration for an app, such as on app boot or container restart. In these cases, you can use the network:rebuild command:
Info
This command will exit a non-zero number that depends on the number of containers for which configuration could not be built
Rebuilding all network settings¶
In some cases, a docker upgrade may reset container IPs or Ports. In both cases, you can quickly rewrite those files by using the network:rebuildall command:
Info
This command will exit a non-zero number that depends on the number of containers for which configuration could not be built
Container network interface binding¶
Info
This functionality does not control the --network docker flag. Please use the docker-options plugin to manage this flag.
By default, an app will only bind to the internal interface. This behavior can be modified per app by changing the bind-all-interfaces network property.
# bind to the default docker interface (`docker0`) with a random internal ip
# this is the default behavior
dokku network:set node-js-app bind-all-interfaces false
# bind to all interfaces (`0.0.0.0`) on a random port for each upstream port
# this will make the app container directly accessible by other hosts on your network
# ports are randomized for every deploy, e.g. `0.0.0.0:32771->5000/tcp`.
dokku network:set node-js-app bind-all-interfaces true
By way of example, in the default case, each container is bound to the docker interface:
As such, the container's IP address will be an internal IP, and thus it is only accessible on the host itself:
However, you can disable the internal proxying via the network:set command so that it will listen on the host's IP address:
The bind-all-interfaces property can also be set globally. The global default is false, and the global value is used when no app-specific value is set.
The default value may be set by passing an empty value for the option.
Displaying network reports for an app¶
You can get a report about the app's network status using the network:report command:
=====> node-js-app network information
Network attach post create:
Network attach post deploy:
Network bind all interfaces: false
Network computed attach post create:
Network computed attach post deploy:
Network computed bind all interfaces:false
Network computed initial network:
Network computed tld:
Network global attach post create:
Network global attach post deploy:
Network global bind all interfaces:false
Network global initial network:
Network global tld:
Network initial network:
Network tld:
Network web listeners: 172.17.0.1:5000
=====> python-sample network information
Network attach post create:
Network attach post deploy:
Network bind all interfaces: false
Network computed attach post create:
Network computed attach post deploy:
Network computed bind all interfaces:false
Network computed initial network:
Network computed tld:
Network global attach post create:
Network global attach post deploy:
Network global bind all interfaces:false
Network global initial network:
Network global tld:
Network initial network:
Network tld:
Network web listeners: 172.17.0.2:5000
=====> ruby-sample network information
Network attach post create:
Network attach post deploy:
Network bind all interfaces: false
Network computed attach post create:
Network computed attach post deploy:
Network computed bind all interfaces:false
Network computed initial network:
Network computed tld:
Network global attach post create:
Network global attach post deploy:
Network global bind all interfaces:false
Network global initial network:
Network global tld:
Network initial network:
Network tld:
Network web listeners:
You can run the command for a specific app also.
=====> node-js-app network information
Network attach post create:
Network attach post deploy:
Network bind all interfaces: false
Network computed attach post create:
Network computed attach post deploy:
Network computed bind all interfaces:false
Network computed initial network:
Network computed tld:
Network global attach post create:
Network global attach post deploy:
Network global bind all interfaces:false
Network global initial network:
Network global tld:
Network initial network:
Network tld:
Network web listeners: 172.17.0.1:5000
You can pass flags which will output only the value of the specific information you want. For example: