Go-Marathon

Go-marathon is a API library for working with Marathon. It currently supports

Application and group deployment
Helper filters for pulling the status, configuration and tasks
Multiple Endpoint support for HA deployments
Marathon Event Subscriptions and Event Streams

Note: the library is still under active development; users should expect frequent (possibly breaking) API changes for the time being.

It requires Go version 1.5 or higher.

Code Examples

There is also an examples directory in the source which shows hints and snippets of code of how to use it — which is probably the best place to start.

You can use examples/docker-compose.yml in order to start a test cluster.

Creating a client

import (
	marathon "github.com/gambol99/go-marathon"
)

marathonURL := "http://10.241.1.71:8080"
config := marathon.NewDefaultConfig()
config.URL = marathonURL
client, err := marathon.NewClient(config)
if err != nil {
	log.Fatalf("Failed to create a client for marathon, error: %s", err)
}

applications, err := client.Applications()
...

Note, you can also specify multiple endpoint for Marathon (i.e. you have setup Marathon in HA mode and having multiple running)

marathonURL := "http://10.241.1.71:8080,10.241.1.72:8080,10.241.1.73:8080"

The first one specified will be used, if that goes offline the member is marked as "unavailable" and a background process will continue to ping the member until it's back online.

Custom HTTP Client

If you wish to override the http client (by default http.DefaultClient) used by the API; use cases bypassing TLS verification, load root CA's or change the timeouts etc, you can pass a custom client in the config.

marathonURL := "http://10.241.1.71:8080"
config := marathon.NewDefaultConfig()
config.URL = marathonURL
config.HTTPClient = &http.Client{
    Timeout: (time.Duration(10) * time.Second),
    Transport: &http.Transport{
        Dial: (&net.Dialer{
            Timeout:   10 * time.Second,
            KeepAlive: 10 * time.Second,
        }).Dial,
        TLSClientConfig: &tls.Config{
            InsecureSkipVerify: true,
        },
    },
}

Listing the applications

applications, err := client.Applications()
if err != nil {
	log.Fatalf("Failed to list applications")
}

log.Printf("Found %d applications running", len(applications.Apps))
for _, application := range applications.Apps {
	log.Printf("Application: %s", application)
	details, err := client.Application(application.ID)
	assert(err)
	if details.Tasks != nil && len(details.Tasks) > 0 {
		for _, task := range details.Tasks {
			log.Printf("task: %s", task)
		}
		// check the health of the application
		health, err := client.ApplicationOK(details.ID)
		log.Printf("Application: %s, healthy: %t", details.ID, health)
	}
}

Creating a new application

log.Printf("Deploying a new application")
application := marathon.NewDockerApplication().
  Name(applicationName).
  CPU(0.1).
  Memory(64).
  Storage(0.0).
  Count(2).
  AddArgs("/usr/sbin/apache2ctl", "-D", "FOREGROUND").
  AddEnv("NAME", "frontend_http").
  AddEnv("SERVICE_80_NAME", "test_http").
  CheckHTTP("/health", 10, 5)

application.
  Container.Docker.Container("quay.io/gambol99/apache-php:latest").
  Bridged().
  Expose(80).
  Expose(443)

if _, err := client.CreateApplication(application); err != nil {
	log.Fatalf("Failed to create application: %s, error: %s", application, err)
} else {
	log.Printf("Created the application: %s", application)
}

Note: Applications may also be defined by means of initializing a marathon.Application struct instance directly. However, go-marathon's DSL as shown above provides a more concise way to achieve the same.

Scaling application

Change the number of application instances to 4

log.Printf("Scale to 4 instances")
if err := client.ScaleApplicationInstances(application.ID, 4); err != nil {
	log.Fatalf("Failed to delete the application: %s, error: %s", application, err)
} else {
	client.WaitOnApplication(application.ID, 30 * time.Second)
	log.Printf("Successfully scaled the application")
}

Subscription & Events

Request to listen to events related to applications — namely status updates, health checks changes and failures. There are two different event transports controlled by EventsTransport setting with the following possible values: EventsTransportSSE and EventsTransportCallback (default value). See Event Stream and Event Subscriptions for details.

Event Stream

Only available in Marathon >= 0.9.0. Does not require any special configuration or prerequisites.

// Configure client
config := marathon.NewDefaultConfig()
config.URL = marathonURL
config.EventsTransport = marathon.EventsTransportSSE

client, err := marathon.NewClient(config)
if err != nil {
	log.Fatalf("Failed to create a client for marathon, error: %s", err)
}

// Register for events
events := make(marathon.EventsChannel, 5)
err = client.AddEventsListener(events, marathon.EventIDApplications)
if err != nil {
	log.Fatalf("Failed to register for events, %s", err)
}

timer := time.After(60 * time.Second)
done := false

// Receive events from channel for 60 seconds
for {
	if done {
		break
	}
	select {
	case <-timer:
		log.Printf("Exiting the loop")
		done = true
	case event := <-events:
		log.Printf("Received event: %s", event)
	}
}

// Unsubscribe from Marathon events
client.RemoveEventsListener(events)

Event Subscriptions

Requires to start a built-in web server accessible by Marathon to connect and push events to. Consider the following additional settings:

EventsInterface — the interface we should be listening on for events. Default "eth0".
EventsPort — built-in web server port. Default 10001.
CallbackURL — custom callback URL. Default "".

// Configure client
config := marathon.NewDefaultConfig()
config.URL = marathonURL
config.EventsInterface = marathonInterface
config.EventsPort = marathonPort

client, err := marathon.NewClient(config)
if err != nil {
	log.Fatalf("Failed to create a client for marathon, error: %s", err)
}

// Register for events
events := make(marathon.EventsChannel, 5)
err = client.AddEventsListener(events, marathon.EventIDApplications)
if err != nil {
	log.Fatalf("Failed to register for events, %s", err)
}

timer := time.After(60 * time.Second)
done := false

// Receive events from channel for 60 seconds
for {
	if done {
		break
	}
	select {
	case <-timer:
		log.Printf("Exiting the loop")
		done = true
	case event := <-events:
		log.Printf("Received event: %s", event)
	}
}

// Unsubscribe from Marathon events
client.RemoveEventsListener(events)

See events.go for a full list of event IDs.

Contributing

See the contribution guidelines.

ch3lo/go-marathon