dokku memcached

Official memcached plugin for dokku. Currently defaults to installing memcached 1.6.26.

Requirements

• dokku 0.19.x+
• docker 1.8.x

Installation

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

Commands

memcached:app-links <app>                          # list all memcached service links for a given app
memcached:connect <service>                        # connect to the service via the memcached connection tool
memcached:create <service> [--create-flags...]     # create a memcached service
memcached:destroy <service> [-f|--force]           # delete the memcached service/data/container if there are no links left
memcached:enter <service>                          # enter or run a command in a running memcached service container
memcached:exists <service>                         # check if the memcached service exists
memcached:expose <service> <ports...>              # expose a memcached service on custom host:port if provided (random port on the 0.0.0.0 interface if otherwise unspecified)
memcached:info <service> [--single-info-flag]      # print the service information
memcached:link <service> <app> [--link-flags...]   # link the memcached service to the app
memcached:linked <service> <app>                   # check if the memcached service is linked to an app
memcached:links <service>                          # list all apps linked to the memcached service
memcached:list                                     # list all memcached services
memcached:logs <service> [-t|--tail] <tail-num-optional> # print the most recent log(s) for this service
memcached:pause <service>                          # pause a running memcached service
memcached:promote <service> <app>                  # promote service <service> as MEMCACHED_URL in <app>
memcached:restart <service>                        # graceful shutdown and restart of the memcached service container
memcached:set <service> <key> <value>              # set or clear a property for a service
memcached:start <service>                          # start a previously stopped memcached service
memcached:stop <service>                           # stop a running memcached service
memcached:unexpose <service>                       # unexpose a previously exposed memcached service
memcached:unlink <service> <app>                   # unlink the memcached service from the app
memcached: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 memcached:help. Plugin help output in conjunction with any files in the docs/ folder is used to generate the plugin documentation. Please consult the memcached:help command for any undocumented commands.

Basic Usage

create a memcached service

# usage
dokku memcached: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)
• -N|--initial-network INITIAL_NETWORK: the initial network to attach the service to
• -p|--password PASSWORD: override the user-level service password
• -P|--post-create-network NETWORKS: a comma-separated list of networks to attach the service container to after service creation
• -r|--root-password PASSWORD: override the root-level service password
• -S|--post-start-network NETWORKS: a comma-separated list of networks to attach the service container to after service start
• -s|--shm-size SHM_SIZE: override shared memory size for memcached docker container

Create a memcached service named lollipop:

dokku memcached:create lollipop

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

export MEMCACHED_IMAGE="memcached"
export MEMCACHED_IMAGE_VERSION="${PLUGIN_IMAGE_VERSION}"
dokku memcached:create lollipop

You can also specify custom environment variables to start the memcached service in semicolon-separated form.

export MEMCACHED_CUSTOM_ENV="USER=alpha;HOST=beta"
dokku memcached:create lollipop

print the service information

# usage
dokku memcached: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
• --initial-network: show the initial network being connected to
• --links: show the service app links
• --post-create-network: show the networks to attach to after service container creation
• --post-start-network: show the networks to attach to after service container start
• --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 memcached:info lollipop

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

dokku memcached:info lollipop --config-dir
dokku memcached:info lollipop --data-dir
dokku memcached:info lollipop --dsn
dokku memcached:info lollipop --exposed-ports
dokku memcached:info lollipop --id
dokku memcached:info lollipop --internal-ip
dokku memcached:info lollipop --initial-network
dokku memcached:info lollipop --links
dokku memcached:info lollipop --post-create-network
dokku memcached:info lollipop --post-start-network
dokku memcached:info lollipop --service-root
dokku memcached:info lollipop --status
dokku memcached:info lollipop --version

list all memcached services

# usage
dokku memcached:list

List all services:

dokku memcached:list

print the most recent log(s) for this service

# usage
dokku memcached: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 memcached:logs lollipop

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

dokku memcached:logs lollipop --tail

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

dokku memcached:logs lollipop --tail 5

link the memcached service to the app

# usage
dokku memcached: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
• -n|--no-restart "false": whether or not to restart the app on link (default: true)

A memcached 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 memcached: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_MEMCACHED_LOLLIPOP_NAME=/lollipop/DATABASE
DOKKU_MEMCACHED_LOLLIPOP_PORT=tcp://172.17.0.1:11211
DOKKU_MEMCACHED_LOLLIPOP_PORT_11211_TCP=tcp://172.17.0.1:11211
DOKKU_MEMCACHED_LOLLIPOP_PORT_11211_TCP_PROTO=tcp
DOKKU_MEMCACHED_LOLLIPOP_PORT_11211_TCP_PORT=11211
DOKKU_MEMCACHED_LOLLIPOP_PORT_11211_TCP_ADDR=172.17.0.1

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

MEMCACHED_URL=memcached://dokku-memcached-lollipop:11211

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 memcached:link other_service playground

It is possible to change the protocol for MEMCACHED_URL by setting the environment variable MEMCACHED_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 MEMCACHED_DATABASE_SCHEME=memcached2
dokku memcached:link lollipop playground

This will cause MEMCACHED_URL to be set as:

memcached2://dokku-memcached-lollipop:11211

unlink the memcached service from the app

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

flags:

• -n|--no-restart "false": whether or not to restart the app on unlink (default: true)

You can unlink a memcached service:

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

dokku memcached:unlink lollipop playground

set or clear a property for a service

# usage
dokku memcached:set <service> <key> <value>

Set the network to attach after the service container is started:

dokku memcached:set lollipop post-create-network custom-network

Set multiple networks:

dokku memcached:set lollipop post-create-network custom-network,other-network

Unset the post-create-network value:

dokku memcached:set lollipop post-create-network

Service Lifecycle

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

connect to the service via the memcached connection tool

# usage
dokku memcached:connect <service>

Connect to the service via the memcached connection tool:

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

dokku memcached:connect lollipop

enter or run a command in a running memcached service container

# usage
dokku memcached: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 memcached:enter lollipop

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

dokku memcached:enter lollipop touch /tmp/test

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

# usage
dokku memcached: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 memcached:expose lollipop 11211

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

dokku memcached:expose lollipop 127.0.0.1:11211

unexpose a previously exposed memcached service

# usage
dokku memcached:unexpose <service>

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

dokku memcached:unexpose lollipop

promote service as MEMCACHED_URL in

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

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

DOKKU_MEMCACHED_BLUE_URL=memcached://other_service:ANOTHER_PASSWORD@dokku-memcached-other-service:11211/other_service

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

NOTE: this will restart your app

dokku memcached:promote other_service playground

This will replace MEMCACHED_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:

MEMCACHED_URL=memcached://other_service:ANOTHER_PASSWORD@dokku-memcached-other-service:11211/other_service
DOKKU_MEMCACHED_BLUE_URL=memcached://other_service:ANOTHER_PASSWORD@dokku-memcached-other-service:11211/other_service
DOKKU_MEMCACHED_SILVER_URL=memcached://lollipop:SOME_PASSWORD@dokku-memcached-lollipop:11211/lollipop

start a previously stopped memcached service

# usage
dokku memcached:start <service>

Start the service:

dokku memcached:start lollipop

stop a running memcached service

# usage
dokku memcached:stop <service>

Stop the service and removes the running container:

dokku memcached:stop lollipop

pause a running memcached service

# usage
dokku memcached:pause <service>

Pause the running container for the service:

dokku memcached:pause lollipop

graceful shutdown and restart of the memcached service container

# usage
dokku memcached:restart <service>

Restart the service:

dokku memcached:restart lollipop

upgrade service to the specified versions

# usage
dokku memcached: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
• -N|--initial-network INITIAL_NETWORK: the initial network to attach the service to
• -P|--post-create-network NETWORKS: a comma-separated list of networks to attach the service container to after service creation
• -R|--restart-apps "true": whether or not to force an app restart (default: false)
• -S|--post-start-network NETWORKS: a comma-separated list of networks to attach the service container to after service start
• -s|--shm-size SHM_SIZE: override shared memory size for memcached docker container

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

dokku memcached:upgrade lollipop

Service Automation

Service scripting can be executed using the following commands:

list all memcached service links for a given app

# usage
dokku memcached:app-links <app>

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

dokku memcached:app-links playground

check if the memcached service exists

# usage
dokku memcached:exists <service>

Here we check if the lollipop memcached service exists.

dokku memcached:exists lollipop

check if the memcached service is linked to an app

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

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

dokku memcached:linked lollipop playground

list all apps linked to the memcached service

# usage
dokku memcached:links <service>

List all apps linked to the lollipop memcached service.

dokku memcached:links lollipop

Disabling docker image pull calls

If you wish to disable the docker image pull calls that the plugin triggers, you may set the MEMCACHED_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 image pull is disabled.