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marathon-consul    

We no longer develop this project. If you'd like to take over and continue its maintenance, please fork this repository and let us know by Github issues.

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.

Note: In the future release Event Bus (callbacks) will be considered deprecated and eventually removed in favor of Event Stream (SSE). Right now marathon-consul is supporting both solutions. SSE is provided as experimental feature, disabled by default (more).

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

Usage

Marathon masters

• marathon-consul should be installed on all Marathon masters

Mesos agents

• Consul Agents should be available on every Mesos agent.
• 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.

Command healthchecks

Healthchecks commands are registered in Consul with a simple variable substitution.

• $HOST is replaced by task hostname.
• $PORT0, $PORT1... are replaced by port number defined in task.

Using a special shell syntax can break this variable substitution ($HOST, ${PORT0} ...)

Sync

• The scheduled Marathon-consul sync may run in two modes:
  • Only on node that is the current Marathon-leader, marathon-leader parameter should be set to hostname:port the current node appears in the Marathon cluster. This mode is enabled by default and the marathon-leader property is set to the hostname resolved by OS. Note that there is a difference between marathon-leader and marathon-location: marathon-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
• If marathon-consul fails on startup sync and you see following error "Can't get Consul services: No Consul client available in agents cache" it may be caused by empty consul agents cache. If this occurs try configuring --consul-local-agent-host to Consul Master or Consul agent.

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.

SSE Support

While using SSE please consider:

• SSE is using Web module config for queues, event sizes, in the future will be moved to sse module,
• SSE is using marathon-leader config for determining current leader, when this value match leader returned by marathon (/v2/leader endpoint) then SSE is started on this instance,
• when enabled SSE is spawning its own own set of workers and separated dispatcher,
• be advised to disable marathon callback subscription when enabling SSE, otherwise it might result in doubling registers and deregisers.

HTTP callbacks support

Marathon-Consul does not support HTTP callbacks. Marathon deprecated support for HTTP callbacks in 1.4. This mechanism is no longer available starting from Marathon 1.5.

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.

Release

To release new version of marathon-consul follow steps:

1. Commit all changes you need for release to master branch.
2. git checkout master
3. git checkout -b release/<version> e.g., git checkout -b release/1.3.1
4. make version v=<version> e.g., make version v=1.3.1
5. git push
6. Create pull request from branch release/<version> to master.
7. Once pull request gets merged put tag on this commit (remember to update your master with git pull) git tag <version> -f e.g., git tag 1.3.1 -f. Create annotated tag with release notes in it.
8. Travis will automatically prepare github release from tag on master. Go there and update release notes.
9. Copy github release to bintray.

License

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