mesosdns-http-agent

A http.Agent which makes it possible to consume Mesos service resources by simply using the Mesos DNS service names.

Usage

Basic usage

To use the mesosdns-http-agent package together with the request module, you can simple modify the Request.defaults(). This will then use the same configuration with every request. Minimally, you'll have to configure one or more Mesos DNS server IPs:

var MesosDNSAgent = require("mesosdns-http-agent"),
    Request = require("request");

var request = Request.defaults({
    agentClass: MesosDNSAgent,
    agentOptions: {
        "dnsServers": ["192.168.0.101", "192.168.0.101", "192.168.0.102"],
        "mesosTLD": ".mesos" // This is optional, the mesosdns-client default is .mesos
    },
    pool: {}
});

var start1 = new Date().getTime();
// Will just use the globalAgent because the TLD is not associated with Mesos DNS
request("http://pkg.freebsd.org/", function(error, response, body) {
    if (error) console.log(error);
    console.log("First call took " + (new Date().getTime()-start1));
});

var start2 = new Date().getTime();
// Will use the mesosdns-http-agent
request("http://web.marathon.mesos/", function(error, response, body) {
    if (error) {
        console.log(error);
    } else {
        console.log("Call took " + (new Date().getTime()-start2) + 'ms with status ' + response.statusCode);
        console.log(body);
    }
});

You can use all available options of the mesosdns-client package.

Advanced usage

By default, the mesosdns-client will always use the first port which is returned for each service (instance). There may be applications which require to use another exposed port, for example if a dockerized app (in bridged mode) was started on Marathon which exposes multiple containerPort values. This is also important if you defined the Request.defaults(), but also want to be able to use other Marathon app's ports within the same Node.js application.

Then, you can create an options object like the following to define the port index to be used by setting the defaultPortIndex property to the desired value (look in the Marathon UI to compare).

var MesosDNSAgent = require("mesosdns-http-agent"),
    request = require("request");
    
var options = {
    agentClass: MesosDNSAgent,
    agentOptions: {
        "dnsServers": ["192.168.0.101", "192.168.0.101", "192.168.0.102"],
        "defaultPortIndex": 1
    },
    url: "http://web.marathon.mesos/"
};

var start = new Date().getTime();
request(options, function(error, response, body) {
    if (error) console.log(error);
    console.log(body);
    console.log("Call took " + (new Date().getTime()-start));
});