Simple etcd client with tests

etcd.js

var request = require("request");
var qstr    = require("querystring").stringify;
var Args    = require("args-js");
var utils   = require("../utils");

var etcd     = module.exports = {};
var watchers = etcd.watchers  = {};

var timeout_code = "ESOCKETTIMEDOUT";

etcd.host     = process.env.ETCDHOST || "127.0.0.1";
etcd.port     = process.env.ETCDPORT || "4001";
etcd.protocol = "http";

etcd.getURL = function(key, params) {
    for (var k in params) {
        if (params[k] === undefined) delete params[k];
    }
    return this.protocol + "://" + this.host + ":" + this.port + "/v2/keys/" + key + (params ? "?" + qstr(params) : "");
};

etcd.watch = function() {
    var args = Args([
        {key:  Args.STRING   | Args.Required},
        {done: Args.FUNCTION | Args.Required}
    ], arguments);

    var url = etcd.getURL(args.key, {
        wait: true
    });

    watchers[args.key] = watcher;
    watcher();

    function watcher() {
        if (!watchers[args.key]) return;
        request.get(url, function(error, res, body) {
            if (error && error.code === timeout_code) return watcher();
            args.done(utils.parseJSON(body));
            watcher();
        });
    }
};

etcd.unwatch = function(key) {
    watchers[key] = undefined;
};

etcd.set = function() {
    var original_arguments = arguments;
    var args = Args([
        {key: Args.STRING | Args.Required},
        [
            {value: Args.STRING | Args.Required},
            {value: Args.OBJECT | Args.Required},
        ],
        {prevValue: Args.STRING   | Args.Optional},
        {prevExist: Args.BOOL     | Args.Optional},
        {done:      Args.FUNCTION | Args.Optional}
    ], arguments);

    if (typeof args.value === "object") {
        args.value = JSON.stringify(args.value);
    }

    request.put(etcd.getURL(args.key, {
        value:     args.value,
        prevValue: args.prevValue,
        prevExist: args.prevExist
    }), function(error, res, body) {
        if (error && error.code === timeout_code) return etcd.set.apply(etcd, original_arguments);
        if (args.done) args.done(utils.parseJSON(body));
    });
};

etcd.get = function() {
    var original_arguments = arguments;
    var args = Args([
        {key:  Args.STRING   | Args.Required},
        {done: Args.FUNCTION | Args.Required}
    ], arguments);

    request.get(etcd.getURL(args.key), function(error, res, body) {
        if (error && error.code === timeout_code) return etcd.get.apply(etcd, original_arguments);
        args.done(utils.parseJSON(body));
    });
};

etcd_test.js

var etcd   = require("./etcd");
var assert = require("assert");

var tests = [];

tests.push(function(done) {
    console.log("\nCASE1: watch and set");

    etcd.watch("hello", function(data) {
        assert.equal(data.node.value, "world!");
        done();
    });

    etcd.set("hello", "world!");
    etcd.unwatch("hello");
});

tests.push(function(done) {
    console.log("\nCASE2: compareAndSwap checkSwap");
    // As in https://github.com/coreos/etcd/blob/master/Documentation/api.md#atomic-compare-and-swap

    // Here is a simple example. Let's create a key-value pair first: `hello=one`.
    etcd.set("hello", "one");

    // Trying to set this existing key with prevExist=false fails as expected:
    etcd.set("hello", "three", false, function(data) {
        // The error code explains the problem:
        assert.equal(data.errorCode, 105);
        assert.equal(data.message, "Key already exists");

        // Now let's provide a prevValue parameter:
        etcd.set("hello", "three", "two", function(data) {
            assert.equal(data.errorCode, 101);
            assert.equal(data.cause, "[two != one]");
            // which means CompareAndSwap failed. cause explains why the test failed. Note: the condition prevIndex=0 always passes.

            // Let's try a valid condition:
            etcd.set("hello", "two", "one", function(data) {
                assert.equal(data.node.value, "two");
                assert.equal(data.prevNode.value, "one");
                done();
            });
        });
    });

});

tests.push(function(done) {
    console.log("\nCASE3: etcd.get");

    // Here is a simple example. Let's create a key-value pair first: `hello=one`.
    etcd.get("hello", function(data) {
        // console.log(data);
        assert.equal(data.node.value, "two");
        done();
    });

});

function callNext() {
    var test = tests.shift();
    if (test) {
        test(function() {
            console.log("DONE!");
            callNext();
        });
    }
}

callNext();