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.

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"
],

• 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.

Task heathchecks

• 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

Argument	Default	Description
config-file		Path to a JSON file to read configuration from. Note: Will override options set earlier on the command line
consul-auth	false	Use Consul with authentication
consul-auth-password		The basic authentication password
consul-auth-username		The basic authentication username
consul-name-separator	.	Separator used to create default service name for Consul
consul-get-services-retry	3	Number of retries on failure when performing requests to Consul. Each retry uses different cached agent
consul-max-agent-failures	3	Max number of consecutive request failures for agent before removal from cache
consul-port	8500	Consul port
consul-ssl	false	Use HTTPS when talking to Consul
consul-ssl-ca-cert		Path to a CA certificate file, containing one or more CA certificates to use to validate the certificate sent by the Consul server to us
consul-ssl-cert		Path to an SSL client certificate to use to authenticate to the Consul server
consul-ssl-verify	true	Verify certificates when connecting via SSL
consul-tag	marathon	Common tag name added to every service registered in Consul, should be unique for every Marathon-cluster connected to Consul
consul-timeout	3s	Time limit for requests made by the Consul HTTP client. A Timeout of zero means no timeout
consul-token		The Consul ACL token
events-queue-size	1000	Size of events queue
listen	:4000	Accept connections at this address
log-file		Save logs to file (e.g.: /var/log/marathon-consul.log). If empty logs are published to STDERR
log-format	text	Log format: JSON, text
log-level	info	Log level: panic, fatal, error, warn, info, or debug
marathon-location	localhost:8080	Marathon URL
marathon-password		Marathon password for basic auth
marathon-protocol	http	Marathon protocol (http or https)
marathon-ssl-verify	true	Verify certificates when connecting via SSL
marathon-timeout	30s	Time limit for requests made by the Marathon HTTP client. A Timeout of zero means no timeout
marathon-username		Marathon username for basic auth
metrics-interval	30s	Metrics reporting interval
metrics-location		Graphite URL (used when metrics-target is set to graphite)
metrics-prefix	default	Metrics prefix (default is resolved to .<app_name>
metrics-target	stdout	Metrics destination stdout or graphite (empty string disables metrics)
sync-enabled	true	Enable Marathon-consul scheduled sync
sync-force	false	Force leadership-independent Marathon-consul sync (run always)
sync-interval	15m0s	Marathon-consul sync interval
sync-leader		Marathon cluster-wide node name (defaults to :8080), the sync will run only if the specified node is the current Marathon-leader
workers-pool-size	10	Number of concurrent workers processing events

Endpoints

Endpoint	Description
/health	healthcheck - returns OK
/events	event sink - returns OK if all keys are set in an event, error message otherwise

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)