dokku nats

Official nats plugin for dokku. Currently defaults to installing nats 2.8.4.

Requirements

• dokku 0.19.x+
• docker 1.8.x

Installation

# on 0.19.x+
sudo dokku plugin:install https://github.com/dokku/dokku-nats.git nats

Commands

nats:app-links <app>                               # list all nats service links for a given app
nats:create <service> [--create-flags...]          # create a nats service
nats:destroy <service> [-f|--force]                # delete the nats service/data/container if there are no links left
nats:enter <service>                               # enter or run a command in a running nats service container
nats:exists <service>                              # check if the nats service exists
nats:expose <service> <ports...>                   # expose a nats service on custom host:port if provided (random port on the 0.0.0.0 interface if otherwise unspecified)
nats:info <service> [--single-info-flag]           # print the service information
nats:link <service> <app> [--link-flags...]        # link the nats service to the app
nats:linked <service> <app>                        # check if the nats service is linked to an app
nats:links <service>                               # list all apps linked to the nats service
nats:list                                          # list all nats services
nats:logs <service> [-t|--tail] <tail-num-optional> # print the most recent log(s) for this service
nats:promote <service> <app>                       # promote service <service> as NATS_URL in <app>
nats:restart <service>                             # graceful shutdown and restart of the nats service container
nats:start <service>                               # start a previously stopped nats service
nats:stop <service>                                # stop a running nats service
nats:unexpose <service>                            # unexpose a previously exposed nats service
nats:unlink <service> <app>                        # unlink the nats service from the app
nats:upgrade <service> [--upgrade-flags...]        # upgrade service <service> to the specified versions

Usage

Help for any commands can be displayed by specifying the command as an argument to nats:help. Plugin help output in conjunction with any files in the docs/ folder is used to generate the plugin documentation. Please consult the nats:help command for any undocumented commands.

Basic Usage

create a nats service

# usage
dokku nats:create <service> [--create-flags...]

flags:

• -c|--config-options "--args --go=here": extra arguments to pass to the container create command (default: None)
• -C|--custom-env "USER=alpha;HOST=beta": semi-colon delimited environment variables to start the service with
• -i|--image IMAGE: the image name to start the service with
• -I|--image-version IMAGE_VERSION: the image version to start the service with
• -m|--memory MEMORY: container memory limit in megabytes (default: unlimited)
• -p|--password PASSWORD: override the user-level service password
• -r|--root-password PASSWORD: override the root-level service password
• -s|--shm-size SHM_SIZE: override shared memory size for nats docker container

Create a nats service named lollipop:

dokku nats:create lollipop

You can also specify the image and image version to use for the service. It must be compatible with the nats image.

export NATS_IMAGE="nats"
export NATS_IMAGE_VERSION="${PLUGIN_IMAGE_VERSION}"
dokku nats:create lollipop

You can also specify custom environment variables to start the nats service in semi-colon separated form.

export NATS_CUSTOM_ENV="USER=alpha;HOST=beta"
dokku nats:create lollipop

print the service information

# usage
dokku nats:info <service> [--single-info-flag]

flags:

• --config-dir: show the service configuration directory
• --data-dir: show the service data directory
• --dsn: show the service DSN
• --exposed-ports: show service exposed ports
• --id: show the service container id
• --internal-ip: show the service internal ip
• --links: show the service app links
• --service-root: show the service root directory
• --status: show the service running status
• --version: show the service image version

Get connection information as follows:

dokku nats:info lollipop

You can also retrieve a specific piece of service info via flags:

dokku nats:info lollipop --config-dir
dokku nats:info lollipop --data-dir
dokku nats:info lollipop --dsn
dokku nats:info lollipop --exposed-ports
dokku nats:info lollipop --id
dokku nats:info lollipop --internal-ip
dokku nats:info lollipop --links
dokku nats:info lollipop --service-root
dokku nats:info lollipop --status
dokku nats:info lollipop --version

list all nats services

# usage
dokku nats:list 

List all services:

dokku nats:list

print the most recent log(s) for this service

# usage
dokku nats:logs <service> [-t|--tail] <tail-num-optional>

flags:

• -t|--tail [<tail-num>]: do not stop when end of the logs are reached and wait for additional output

You can tail logs for a particular service:

dokku nats:logs lollipop

By default, logs will not be tailed, but you can do this with the --tail flag:

dokku nats:logs lollipop --tail

The default tail setting is to show all logs, but an initial count can also be specified:

dokku nats:logs lollipop --tail 5

link the nats service to the app

# usage
dokku nats:link <service> <app> [--link-flags...]

flags:

• -a|--alias "BLUE_DATABASE": an alternative alias to use for linking to an app via environment variable
• -q|--querystring "pool=5": ampersand delimited querystring arguments to append to the service link

A nats service can be linked to a container. This will use native docker links via the docker-options plugin. Here we link it to our playground app.

NOTE: this will restart your app

dokku nats:link lollipop playground

The following environment variables will be set automatically by docker (not on the app itself, so they won’t be listed when calling dokku config):

DOKKU_NATS_LOLLIPOP_NAME=/lollipop/DATABASE
DOKKU_NATS_LOLLIPOP_PORT=tcp://172.17.0.1:4222
DOKKU_NATS_LOLLIPOP_PORT_4222_TCP=tcp://172.17.0.1:4222
DOKKU_NATS_LOLLIPOP_PORT_4222_TCP_PROTO=tcp
DOKKU_NATS_LOLLIPOP_PORT_4222_TCP_PORT=4222
DOKKU_NATS_LOLLIPOP_PORT_4222_TCP_ADDR=172.17.0.1

The following will be set on the linked application by default:

NATS_URL=nats://lollipop:SOME_PASSWORD@dokku-nats-lollipop:4222

The host exposed here only works internally in docker containers. If you want your container to be reachable from outside, you should use the expose subcommand. Another service can be linked to your app:

dokku nats:link other_service playground

It is possible to change the protocol for NATS_URL by setting the environment variable NATS_DATABASE_SCHEME on the app. Doing so will after linking will cause the plugin to think the service is not linked, and we advise you to unlink before proceeding.

dokku config:set playground NATS_DATABASE_SCHEME=nats2
dokku nats:link lollipop playground

This will cause NATS_URL to be set as:

nats2://lollipop:SOME_PASSWORD@dokku-nats-lollipop:4222

unlink the nats service from the app

# usage
dokku nats:unlink <service> <app>

You can unlink a nats service:

NOTE: this will restart your app and unset related environment variables

dokku nats:unlink lollipop playground

Service Lifecycle

The lifecycle of each service can be managed through the following commands:

enter or run a command in a running nats service container

# usage
dokku nats:enter <service>

A bash prompt can be opened against a running service. Filesystem changes will not be saved to disk.

NOTE: disconnecting from ssh while running this command may leave zombie processes due to moby/moby#9098

dokku nats:enter lollipop

You may also run a command directly against the service. Filesystem changes will not be saved to disk.

dokku nats:enter lollipop touch /tmp/test

expose a nats service on custom host:port if provided (random port on the 0.0.0.0 interface if otherwise unspecified)

# usage
dokku nats:expose <service> <ports...>

Expose the service on the service's normal ports, allowing access to it from the public interface (0.0.0.0):

dokku nats:expose lollipop 4222

Expose the service on the service's normal ports, with the first on a specified ip adddress (127.0.0.1):

dokku nats:expose lollipop 127.0.0.1:4222

unexpose a previously exposed nats service

# usage
dokku nats:unexpose <service>

Unexpose the service, removing access to it from the public interface (0.0.0.0):

dokku nats:unexpose lollipop

promote service as NATS_URL in

# usage
dokku nats:promote <service> <app>

If you have a nats service linked to an app and try to link another nats service another link environment variable will be generated automatically:

DOKKU_NATS_BLUE_URL=nats://other_service:ANOTHER_PASSWORD@dokku-nats-other-service:4222/other_service

You can promote the new service to be the primary one:

NOTE: this will restart your app

dokku nats:promote other_service playground

This will replace NATS_URL with the url from other_service and generate another environment variable to hold the previous value if necessary. You could end up with the following for example:

NATS_URL=nats://other_service:ANOTHER_PASSWORD@dokku-nats-other-service:4222/other_service
DOKKU_NATS_BLUE_URL=nats://other_service:ANOTHER_PASSWORD@dokku-nats-other-service:4222/other_service
DOKKU_NATS_SILVER_URL=nats://lollipop:SOME_PASSWORD@dokku-nats-lollipop:4222/lollipop

start a previously stopped nats service

# usage
dokku nats:start <service>

Start the service:

dokku nats:start lollipop

stop a running nats service

# usage
dokku nats:stop <service>

Stop the service and the running container:

dokku nats:stop lollipop

graceful shutdown and restart of the nats service container

# usage
dokku nats:restart <service>

Restart the service:

dokku nats:restart lollipop

upgrade service to the specified versions

# usage
dokku nats:upgrade <service> [--upgrade-flags...]

flags:

• -c|--config-options "--args --go=here": extra arguments to pass to the container create command (default: None)
• -C|--custom-env "USER=alpha;HOST=beta": semi-colon delimited environment variables to start the service with
• -i|--image IMAGE: the image name to start the service with
• -I|--image-version IMAGE_VERSION: the image version to start the service with
• -R|--restart-apps "true": whether to force an app restart
• -s|--shm-size SHM_SIZE: override shared memory size for nats docker container

You can upgrade an existing service to a new image or image-version:

dokku nats:upgrade lollipop

Service Automation

Service scripting can be executed using the following commands:

list all nats service links for a given app

# usage
dokku nats:app-links <app>

List all nats services that are linked to the playground app.

dokku nats:app-links playground

check if the nats service exists

# usage
dokku nats:exists <service>

Here we check if the lollipop nats service exists.

dokku nats:exists lollipop

check if the nats service is linked to an app

# usage
dokku nats:linked <service> <app>

Here we check if the lollipop nats service is linked to the playground app.

dokku nats:linked lollipop playground

list all apps linked to the nats service

# usage
dokku nats:links <service>

List all apps linked to the lollipop nats service.

dokku nats:links lollipop

Disabling docker pull calls

If you wish to disable the docker pull calls that the plugin triggers, you may set the NATS_DISABLE_PULL environment variable to true. Once disabled, you will need to pull the service image you wish to deploy as shown in the stderr output.

Please ensure the proper images are in place when docker pull is disabled.