Deployer

A REST API for updating Docker services with a new image. Running docker service update the fancy way.

Add this server to the end of your CD workflow, and maybe life will be a little easier. A token (via HTTP headers) is used for authorisation and notifications are pushed into beanstalkd; so you can write any type of notifier you want.

Running deployer

There is an external requirement on beanstalkd for sending notifications (it probably works without it, but we haven't tried). beanstalkd is pretty easy to setup.

All requests to the server should be done over SSL; we use a SSL termination proxy and no doubt you have something similar setup.

Server flags/options

TOKEN

This string must be provided via the Authorization HTTP header for any update request to stand a chance of succeeding.

DOCKER_HOST

Address of the Docker daemon - this must be a Swarm manager node.

NOTIFY_FLAGS

This one is a bit more tricky; flags that will be passed to the notification system. Currently only beanstalkd is supported and the string must be in JSON format.

{
  "addr": "addr_to_beanstalkd:11300",
  "tube": "name_of_tube_to_put_messages_into",
  "template": "base64 encoded message to put into beanstalk, available variables are {{.Artifact}} and {{.ServiceName}}"
}

So to push the message I just deployed image/name:tag to service_name you would write the template "I just deployed {{.Artifact}} for {{.ServiceName}} and base64 encode it.

{
  "addr": "beanstalk:11300",
  "tube": "jobs",
  "template": "IkkganVzdCBkZXBsb3llZCB7ey5BcnRpZmFjdH19IGZvciB7ey5TZXJ2aWNlTmFtZX19"
}

BIND

Local address for the server to bind to.

Starting the service

We will run deployer as a Docker service, ensuring it has access to the host node's Docker daemon and only on Swarm manager nodes.

$ docker service create --name deployer --network your_overlay_network --mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock --constraint 'node.role == manager' --env NOTIFY_FLAGS='{"addr": "beanstalk:11300","tube": "jobs","template": "IkkganVzdCBkZXBsb3llZCB7ey5BcnRpZmFjdH19IGZvciB7ey5TZXJ2aWNlTmFtZX19"}' --env TOKEN=SPECIFIY_SOME_TOKEN_HERE symfoni/deployer:latest

Point your proxy to the server

It is assumed you know how to do this.

Marking services as being updatable

Add the following label to the service: deployer.allowUpdates=true.

$ docker service update --label-add 'deployer.allowUpdates=true' service_name

Notifications

As mentioned already, notifications are sent via beanstalkd (see NOTIFY_FLAGS on how to configure). You will need a consumer to process these messages, and that consumer canthen do anything it wants with it (send to Slack, email, IRC etc.). A notification will be sent if we get a successful response back from the Docker API, this doesn't mean that the actual deployment was a success.

Using the server

Only PUT requests to the /service/:service-name endpoint will do anything. You need to include a JSON payload with the request in the following format:

{
  "image": "nameofimage:tag"
}

That will update :service-name to use the image nameofimage:tag.

curl example

This will update our service blog with image me/blog:v1.12. This command is run by our CD server after a successfull image hub push.

$ curl -v --header "Authorization: SPECIFIY_SOME_TOKEN_HERE" -X PUT -d '{"image": "me/blog:v1.12"}' https://your.deployment.url/service/blog

Compiling a binary

You need Go > v1.7, we typed the following and got a nice binary:

$ CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -ldflags '-w -extld ld -extldflags -static' -a -x -o deployer .