eventhubs-js/client.js

Easy to use client for Azure event hubs

var Q = require("q"),
    http = require('https'),
	https = require('https'),
	crypto = require('crypto'),
	moment = require('moment');

var namespace,
    hubName,
    keyName,
    key,
    sasToken,
	sasTokens = {}; //key=uri, value=SAS token

function getSasToken(uri) {
    if(sasToken) {
        return sasToken;
    }

    var expiration,
        toSign,
		hmac,
		encodedHmac,
		token;

	//Cache tokens to avoid recalculations
    token = sasTokens[uri];

    // remove expired tokens from the cache
	if(token && moment().unix()  < token.expiration) {
		return token.token;
	}

    expiration = moment().add(15, 'days').unix();
    
    toSign = encodeURIComponent(uri) + '\n' + expiration;
    hmac = crypto.createHmac('sha256', key);
    hmac.update(toSign);
	encodedHmac = hmac.digest('base64');

    token = 'SharedAccessSignature sr=' + encodeURIComponent(uri) + '&sig=' + encodeURIComponent(encodedHmac) + '&se=' + expiration + '&skn=' + keyName;

	sasTokens[uri] = {
        token: token,
        expiration: expiration
    };

    console.log('Generated SAS token "' + token + '"');

	return token;
}

//https://msdn.microsoft.com/en-us/library/azure/dn790664.aspx
function getDeviceUri(deviceId) {
    var uri = null;
    if (!deviceId) {
        uri = 'https://' + namespace
            + '.servicebus.windows.net' + '/' + hubName + '/messages';    
    } else {
        uri = 'https://' + namespace
            + '.servicebus.windows.net' + '/' + hubName
            + '/publishers/' + encodeURIComponent(deviceId) + '/messages';    
    }
    return uri;
}

//hubNamespace, hubName, keyName, key
function init(options) {
    namespace = options.hubNamespace;
    hubName = options.hubName;
    keyName = options.keyName;
    key = options.key;
    sasToken = options.sasToken;

    //Allow the connection pool to grow larger. This improves performance
    //by a factor of 10x in my testing
    http.globalAgent.maxSockets = 50;
}

function sendMessage(messageObject) {
	var message = messageObject.message,
		deviceId = messageObject.deviceId,
	    payload;
    
    if (typeof message === 'string') {
        payload = message;
    } else {
        //This allows us to send in a POJSO
        payload = JSON.stringify(message);
    }

    return send(payload, deviceId);
}

function sendMessages(messageObject) {
    var messages = messageObject.messages,
		deviceId = messageObject.deviceId,
        payload;

    if (messages.length === 0)
        throw new Error("Given argument contains no messages!");
    
    payload = JSON.stringify(messages);

    return send(payload, deviceId);
}

function send(payload, deviceId) {
    var deferral,
		requestOptions,
		deviceUri,
        token,
        req,
        responseData = '';

    deferral = Q.defer();

    deviceUri = getDeviceUri(deviceId);
    token = getSasToken(deviceUri);

    requestOptions = {
        hostname: namespace + '.servicebus.windows.net',
        port: 443,
        path: deviceId ? '/' + hubName + '/publishers/' + deviceId + '/messages' : '/' + hubName + '/messages',
        method: 'POST',
        headers: {
            'Authorization': token,
            'Content-Length': Buffer.byteLength(payload),
            'Content-Type': 'application/atom+xml;type=entry;charset=utf-8'
        }
    }

    req = https.request(requestOptions, function (res) {
        res.on('data', function (data) {
            responseData += data;
        }).on('end', function () {
            if (res.statusCode !== 201) {
                deferral.reject(new Error("Invalid server status: " + res.statusCode + "Message: " + responseData));
                return;
            }

            deferral.resolve({
                statusCode: res.statusCode,
                responseData: responseData
            });
        }).on('error', function (e) {
            deferral.reject(e);
        });
    });
    
    req.on('error', function(e){
    	deferral.reject(e);
    });

    req.setSocketKeepAlive(true);
    req.write(payload);
    req.end();

    return deferral.promise;
}

exports.init = init;
exports.sendMessage = sendMessage;
exports.sendMessages = sendMessages;