brndnmtthws / marathon-lb

marathon-lb

Script to update haproxy based on marathon state.

You can run the script directly or using the Docker image.

Architecture

The marathon-lb script marathon-update-haproxy.py connect to the marathon API to retrieve all apps running, generates a haproxy config and reloads haproxy. By default, marathon-lb binds to the service port of every application and sends incoming requests to the application instances. To create a virtual host the HAPROXY_0_VHOST label needs to be set on the given application.

See comments in script for all available options.

Deployment

To deploy the marathon-lb on the public slaves in your DCOS cluster, simply run:

dcos package install marathon-lb

To configure a custom ssl-certificate, set the dcos cli option ssl-cert to your concatenated cert and private key in .pem format. For more details see the haproxy documentation.

For further customization, templates can be added by pointing the dcos cli option template-url to a tarball containing a directory templates/. See comments in script on how to name those.

Caveats and Limitations

Since marathon-lb needs to bind to the service ports dynamically and allocating them is not possible with a simple marathon scheduled application, this implementation it prone to port conflicts. To avoid those, ideally you only run this service in your public slaves.

Docker

Synopsis: docker run mesosphere/marathon-lb event|poll ...

You can pass in your own certificates for the SSL frontend by setting the HAPROXY_SSL_CERT environment variable.

sse mode

In SSE mode, the script connects to the marathon events endpoint to get notified about state changes.

Syntax: docker run mesosphere/marathon-lb sse [other args]

event mode

In event mode, the script registers a http callback in marathon to get notified when state changes.

Syntax: docker run mesosphere/marathon-lb event callback-addr:port [other args]

poll mode

If you can't use the http callbacks, the script can poll the APIs to get the schedulers state periodically.

Synatax: docker run mesosphere/marathon-lb poll [other args]

To change the poll interval (defaults to 60s), you can set the POLL_INTERVALL environment variable.

Direct invocation

You can also run the update script directly. To generate an HAProxy configuration from Marathon running at localhost:8080 with the marathon-update-haproxy.py script, run:

$ ./marathon-update-haproxy.py --marathon http://localhost:8080 --haproxy-config /etc/haproxy/haproxy.cfg

This will refresh haproxy.cfg, and if there were any changes, then it will automatically reload HAproxy.

marathon-update-haproxy.py has a lot of additional functionality like sticky sessions, HTTP to HTTPS redirection, SSL offloading, VHost support and templating capabilities.

To get the full documentation run:

$ ./marathon-update-haproxy.py --help