libvmod-marathon

Description

This module dynamically fetches applications from Mesosphere Marathon and makes them available as backends in your Varnish VCL.

It monitors Marathon's SSE eventbus and makes sure that the backends is always kept in a consistent state without requiring to reload Varnish.

Usage

new my_marathon = marathon.server(endpoint = "http://marathon.domain.tld",[default appconfig options])

Available options

Parameter	Description	Default
endpoint	URL to Marathon	Null (required)
connect_timeout	connect_timeout	Varnish default
first_byte_timeout	first_byte_timeout	Varnish default
between_bytes_timeout	between_bytes_timeout	Varnish default
max_connections	max_connections	Varnish default
proxy_header	proxy_header	Varnish default

Object methods

.set_backend_config(id="/myapp", options)

Options

Parameter	Description	Default
port_index	Port index to use	0
probe	Varnish probe	None
connect_timeout	connect_timeout	Varnish default
first_byte_timeout	first_byte_timeout	Varnish default
between_bytes_timeout	between_bytes_timeout	Varnish default
max_connections	max_connections	Varnish default
proxy_header	proxy_header	Varnish default

Set varnish backend parameters for "/myapp".

.backend_by_id(<id>) Returns a round-robin backend for the application with the given id in Marathon.

.backend_by_label(<labelName>, <labelValue>) Returns a round-robin backend for the application with the label matching in Marathon.

.json_stats() Returns JSON with current backend configuration.

.reload() Reload the module.

Debug logging

Debug logging to syslog can be enabled with marathon.debug_log(1);

Healthchecks

If an application has healthchecks configured in Marathon the module will respect it and only send traffic to tasks marked as healthy by Marathon.

Example VCL

vcl 4.0;

import marathon;

backend dummy {
    .host = "127.0.0.1";
    .port = "8080";
}

sub vcl_init {
  // Enable debug logging.
  marathon.debug_log(1);

  // Connect to Marathon.
  new my_marathon = marathon.server("http://marathon.domain.tld");
}

sub vcl_recv {
  // Set up a endpoint to show backend information.
  if (req.url ~ "^/vmod-marathon.json$") {
    return(synth(700, "OK"));
  }

  // Route traffic to myapp.mysite.tld to application with Marathon ID /myapp.
  if (req.http.Host == "myapp.mysite.tld") {
    set req.backend_hint = my_marathon.backend_by_id("/myapp");
  }

  // Route all other traffic to application in Marathon with label loadbalancer.host matching req.http.Host
  elsif (req.http.Host) {
    set req.backend_hint = my_marathon.backend_by_label("loadbalancer.host", req.http.Host);
  }

  return(pass);
}

sub vcl_synth {
  // Handle statistics endpoint.
  if (resp.status == 700) {
    set resp.status = 200;
    set resp.http.Content-Type = "application/json; charset=utf-8";
    synthetic(vg_marathon.json_stats());
    return(deliver);
  }
}

Installation

Dependencies:

libcurl - the multiprotocol file transfer library.
yajl - Yet Another JSON Library.

The source tree is based on autotools to configure the building.

Building requires the Varnish header files and uses pkg-config to find the necessary paths.

 ./autogen.sh
 ./configure

If you have installed Varnish to a non-standard directory, call autogen.sh and configure with PKG_CONFIG_PATH pointing to the appropriate path. For instance, when varnishd configure was called with --prefix=$PREFIX, use

export PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig
export ACLOCAL_PATH=${PREFIX}/share/aclocal

The module will inherit its prefix from Varnish, unless you specify a different --prefix when running the configure script for this module.

Make targets:

make - builds the vmod.
make install - installs your vmod.

 ./configure
 make
 make install

olekenneth/libvmod-marathon