marathon-consul

marathon-consul    

Register Marathon Tasks as Consul Services for service discovery.

marathon-consul takes information provided by the Marathon event bus and forwards it to Consul agents. It also re-syncs all the information from Marathon to Consul on startup and repeats it with given interval.

Code

This project is based on

• mesos-consul
• marathon-consul

Differences

• CiscoCloud/marathon-consul copies application information to Consul KV while allegro/marathon-consul registers tasks as Consul services (it is more similar to CiscoCloud/mesos-consul)
• CiscoCloud/mesos-consul uses polling while allegro/marathon-consul uses Marathon's event bus to detect changes
• CiscoCloud/marathon-consul is no longer developed (see comment)

Installation

Installing from source code

To simply compile and run the source code:

go run main.go [options]

To run the tests:

make test

To build the binary:

make build

Installing from binary distribution

Binary distribution of marathon-consul can be downloaded directly from the releases page. Download the build dedicated to your OS. After unpacking the archive, run marathon-consul binary. You can also add some options, for example:

marathon-consul --marathon-location=marathon.service.consul:8080 --sync-interval=5m --log-level=debug

Installing via APT package manager

If you are a Debian/Ubuntu user, you can easily install marathon-consul as a deb package using APT package manager. Both upstart and systemd service managers are supported. All releases are published as deb packages to our repository at Bintray.

To install marathon-consul with apt-get, simply follow the instructions:

# add our public key to apt
curl -s https://bintray.com/user/downloadSubjectPublicKey?username=allegro | sudo apt-key add -
# add the repository url
echo "deb http://dl.bintray.com/v1/content/allegro/deb /" | sudo tee /etc/apt/sources.list.d/marathon-consul.list
# update apt cache
sudo apt-get -y update
# install latest release of marathon-consul
sudo apt-get -qy install marathon-consul

Run it with service marathon-consul start. The configuration file is located at /etc/marathon-consul.d/config.json.

Installing with Docker

To build docker image run

make docker

Then you can run it with

docker run -d -P allegro/marathon-consul [options]

If you want to use SSL you will need to expose cert store to Docker. The Following line is only example, your cert store might be different depending on your system.

docker run '/etc/ssl/certs/ca-certificates.crt:/etc/ssl/certs/ca-certificates.crt' -P  allegro/marathon-consul

Setting up marathon-consul after installation

The Marathon event bus should point to /events. You can set up the event subscription with a call similar to this one:

curl -X POST 'http://marathon.service.consul:8080/v2/eventSubscriptions?callbackUrl=http://marathon-consul.service.consul:4000/events'

The event subscription should be set to localhost to reduce network traffic.

Usage

Marathon masters

• marathon-consul should be installed on all Marathon masters

Mesos slaves

• Consul Agents should be available on every Mesos slave.
• Tasks will be registered at the Mesos slave they run on.

Tagging tasks

• Task labels are used by marathon-consul to register tasks in Consul.
• Only tasks which are labeled as consul will be registered in Consul. If the consul label is left blank like "consul": "", the task will be registered with the app name by default. A different name can be provided as the label's value, e.g. "consul": "customName". As an exception to this rule, for backward compatibility with the 0.3.x branch, a value of true is resolved to the default name.

  "id": "my-new-app",
  "labels": {
    "consul": ""
  }

• Only services with tag specified by consul-tag property will be maintained. By default, "consul-tag": "marathon" is automatically added when the task is registered.
• Labels with a value of tag are converted to consul-tags, and appear in Consul as ServiceTags.
• For example, we can set these tags in an app definition like:

  "id": "my-new-app",
  "labels": {
    "consul": "",
    "varnish": "tag",
    "metrics": "tag"
  }

• If marathon-consul registers the app with Consul, we can then query Consul and see these tags appear:

curl -X GET http://localhost:8500/v1/catalog/service/my-new-app
...
"ServiceName": "my-new-app",
"ServiceTags": [
  "marathon",
  "varnish",
  "metrics",
  "marathon-task:my-new-app.6a95bb03-6ad3-11e6-beaf-080027a7aca0"
],

• Every service registration contains an additional tag marathon-task specifying the Marathon task id related to this registration.
• If there are multiple ports in use for the same app, note that only the first one will be registered by marathon-consul in Consul.

If you need to register your task under multiple ports, refer to Advanced usage section below.

Task healthchecks

• At least one HTTP healthcheck should be defined for a task. The task is registered when Marathon marks it as alive.
• The provided HTTP healthcheck will be transferred to Consul.
• See this for more details.

Sync

• The scheduled Marathon-consul sync may run in two modes:
  • Only on node that is the current Marathon-leader, sync-leader parameter should be set to hostname:port the current node appears in the Marathon cluster. This mode is enabled by default and the sync-leader property is set to the hostname resolved by OS. Note that there is a difference between sync-leader and marathon-location: sync-leader is used for node leadership detection (should be set to cluster-wide node name), while marathon-location is used for connection purpose (may be set to localhost)
  • On every node, sync-force parameter should be set to true

Options

Endpoints

Advanced usage

Register under multiple ports

If you need to map your Marathon task into multiple service registrations in Consul, you can configure marathon-consul via Marathon's portDefinitions:

  "id": "my-new-app",
  "labels": {
    "consul": "",
    "common-tag": "tag"
  },
  "portDefinitions": [
    {
      "labels": {
        "consul": "my-app-custom-name"
      }
    },
    {
      "labels": {
        "consul": "my-app-other-name",
        "specific-tag": "tag"
      }
    }
  ]

This configuration would result in two service registrations:

curl -X GET http://localhost:8500/v1/catalog/service/my-app-custom-name
...
"ServiceName": "my-app-custom-name",
"ServiceTags": [
  "marathon",
  "common-tag",
  "marathon-task:my-new-app.6a95bb03-6ad3-11e6-beaf-080027a7aca0"
],
"ServicePort": 31292,
...

curl -X GET http://localhost:8500/v1/catalog/service/my-app-other-name
...
"ServiceName": "my-app-other-name",
"ServiceTags": [
  "marathon",
  "common-tag",
  "specific-tag",
  "marathon-task:my-new-app.6a95bb03-6ad3-11e6-beaf-080027a7aca0"
],
"ServicePort": 31293,
...

If any port definition contains the consul label, then advanced configuration mode is enabled. As a result, only the ports containing this label are registered, under the name specified as the label's value – with empty value resolved to default name. Names don't have to be unique – you can have multiple registrations under the same name, but on different ports, perhaps with different tags. Note that the consul label still needs to be present in the top-level application labels, even though its value won't have any effect.

Tags configured in the top-level application labels will be added to all registrations. Tags configured in the port definition labels will be added only to corresponding registrations.

All registrations share the same marathon-task tag.

Migration to version 1.x.x

Until 1.x.x marathon-consul would register services in Consul with registration id equal to related Marathon task id. Since 1.x.x registration ids are different and an additional tag, marathon-task, is added to each registration.

If you update marathon-consul from version 0.x.x to 1.x.x, expect the synchronization phase during the first startup to reregister all healthy services managed by marathon-consul to the new format. Unhealthy services will get deregistered in the process.

Known limitations

The following section describes known limitations in marathon-consul.

• In Marathon when a deployment changing the application's service name (by changing its labels) is being stopped, it changes app's configuration anyway. This means we loose the link between the app and the services registered with the old name in Consul. Later on, if another deployment takes place, new services are registered with a new name, the old ones are not being deregistered though. A scheduled sync is required to wipe them out.

License

Marathon-consul is released under the Apache 2.0 license (see LICENSE)