marathon-consul

Marathon to Consul bridge for metadata discovery.

marathon-consul takes information provided by the Marathon event bus and
forwards it to Consul's KV tree. It also re-syncs all the information from
Marathon to Consul on startup.

Table of Contents

marathon-consul

Comparison to other metadata bridges

`haproxy-marathon-bridge`

This project has similar goals (to enable metadata usage in templates.) However,
haproxy-marathon-bridge uses cron instead of the event bus, so it only updates
once per minute. It is also limited to haproxy, where marathon-consul in
conjunction with consul-template
can update anything you can write a configuration file for.

Building

docker build -t marathon-consul .

Running

marathon-consul can be run in a Docker container via Marathon. If your Marathon
service is registered in consul, you can use .service.consul to find them,
otherwise change the vaules for your environment:

curl -X POST -d @marathon-consul.json -H "Content-Type: application/json" http://marathon.service.consul:8080/v2/apps'

Where marathon-consul.json is similar to (replacing the image with your image):

{
  "id": "marathon-consul",
  "args": ["--registry=https://consul.service.consul:8500"],
  "container": {
    "type": "DOCKER",
    "docker": {
      "image": "{{ marathon_consul_image }}:{{ marathon_consul_image_tag }}",
      "network": "BRIDGE",
      "portMappings": [{"containerPort": 4000, "hostPort": 4000, "protocol": "tcp"}]
    }
  },
  "constraints": [["hostname", "UNIQUE"]],
  "ports": [4000],
  "healthChecks": [{
    "protocol": "HTTP",
    "path": "/health",
    "portIndex": 0
  }],
  "instances": 1,
  "cpus": 0.1,
  "mem": 128
}

You can also add options to authenticate against Consul.

If your version of Marathon is 0.9.0 or newer, no further setup is required.
Marathon-consul will autodetect the /v2/events endpoint and use it to update
Consul.

If your version of Marathon does not have the event bus endpoint, you must
configure an event subscription. 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'

Usage

Options

Argument	Default	Description
`listen`	:4000	accept connections at this address
`registry`	http://localhost:8500	root location of the Consul registry
`registry-auth`	None	basic auth for the Consul registry
`registry-datacenter`	None	datacenter to use in writes
`registry-token`	None	Consul registry ACL token
`registry-noverify`	False	don't verify registry SSL certificates
`registry-prefix`	`marathon`	prefix for all values sent to the registry
`log-level`	`info`	log level: panic, fatal, error, warn, info, or debug
`marathon-location`	`localhost:8080`	Marathon location (for resyncing)
`marathon-protocol`	`http`	Marathon prototocol (http or https)
`marathon-username`	None	Marathon username for basic auth
`marathon-password`	None	Marathon password for basic auth

Adding New Root Certificate Authorities

If you're running Consul behind an SSL proxy like Nginx, you're probably going
to want to add the CA for your certificate to the trusted store in the container
so you can avoid using --registry-noverify. For that purpose, any certificates
added in a volume at /usr/local/share/ca-certificates/ will be added to the
root certificates in the container on boot.

Endpoints

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

Keys and Values

The entire app configuration is forwarded to Consul as a JSON blob. It might
looks something like this (example from the Marathon documentation):

{
    "id": "/product/service/my-app",
    "cmd": "env && sleep 300",
    "args": ["/bin/sh", "-c", "env && sleep 300"],
    "container": {
        "type": "DOCKER",
        "docker": {
            "image": "group/image",
            "network": "BRIDGE",
            "portMappings": [
                {
                    "containerPort": 8080,
                    "hostPort": 0,
                    "servicePort": 9000,
                    "protocol": "tcp"
                },
                {
                    "containerPort": 161,
                    "hostPort": 0,
                    "protocol": "udp"
                }
            ],
            "privileged": false,
            "parameters": [
                { "key": "a-docker-option", "value": "xxx" },
                { "key": "b-docker-option", "value": "yyy" }
            ]
        },
        "volumes": [
            {
                "containerPath": "/etc/a",
                "hostPath": "/var/data/a",
                "mode": "RO"
            },
            {
                "containerPath": "/etc/b",
                "hostPath": "/var/data/b",
                "mode": "RW"
            }
        ]
    },
    "cpus": 1.5,
    "mem": 256.0,
    "env": {
        "LD_LIBRARY_PATH": "/usr/local/lib/myLib"
    },
    "executor": "",
    "constraints": [
        ["attribute", "OPERATOR", "value"]
    ],
    "labels": {
        "environment": "staging"
    },
    "healthChecks": [
        {
            "protocol": "HTTP",
            "path": "/health",
            "gracePeriodSeconds": 3,
            "intervalSeconds": 10,
            "portIndex": 0,
            "timeoutSeconds": 10,
            "maxConsecutiveFailures": 3
        },
        {
            "protocol": "TCP",
            "gracePeriodSeconds": 3,
            "intervalSeconds": 5,
            "portIndex": 1,
            "timeoutSeconds": 5,
            "maxConsecutiveFailures": 3
        },
        {
            "protocol": "COMMAND",
            "command": { "value": "curl -f -X GET http://$HOST:$PORT0/health" },
            "maxConsecutiveFailures": 3
        }
    ],
    "instances": 3,
    "ports": [
        8080,
        9000
    ],
    "backoffSeconds": 1,
    "backoffFactor": 1.15,
    "uris": [
        "https://raw.github.com/mesosphere/marathon/master/README.md"
    ],
    "dependencies": ["/product/db/mongo", "/product/db", "../../db"],
    "upgradeStrategy": {
        "minimumHealthCapacity": 0.5,
        "maximumOverCapacity": 0.2
    },
    "version": "2014-03-01T23:29:30.158Z"
}

License

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