zmq-service-suite-broker/lib/frontend.js

0MQ Service oriented Suite - Broker

var zmq = require('zeromq'),
    errors = require('../config/errors'),
    metric = require('./metric'),
    Logger = require('logger-facade-nodejs'),
    _ = require('lodash'),
    Message = require('zmq-service-suite-message'),
    msgpack = require('msgpack-js');

var IDENTITY_FRAME = 0,
    PROTOCOL_FRAME = 1,
    TYPE_FRAME     = 2,
    RID_FRAME      = 3,
    ADDRESS_FRAME  = 4,
    HEADERS_FRAME  = 5,
    STATUS_FRAME   = 6,
    PAYLOAD_FRAME  = 7;

var Frontend = function(configuration, smiService){
  var instance;

  var log = Logger.getLogger('Frontend');

  var defaults = {
    frontend: 'tcp://127.0.0.1:5560'
  };

  var config = _.defaults(configuration, defaults);
  var frontend;

  var reply = function(message){
    message.type = Message.Type.REP;

    message = metric.feEnd(message);

    log.info("replied to: %s with status: %s for rid: %s", message.identity, message.status, message.rid);

    // TODO: log frames in debug mode
    // if(log.isDebug()) {
    //   //log.debug(message.toString());
    // }

    frontend.send(message.toFrames());
  };

  var replyFrames = function(frames){
    frames[TYPE_FRAME] = Message.Type.REP;

    frames = metric.feEnd(frames);

    var identity = frames[IDENTITY_FRAME];
    var status = frames[STATUS_FRAME];
    var rid = frames[RID_FRAME];

    log.info("replied to: %s with status: %s for rid: %s", identity, status, rid);

    // TODO: log frames in debug mode
    // if(log.isDebug()) {
    //   var message = Message.parse(frames);
    //   log.debug(message.toString());
    // }

    frontend.send(frames);
  };

  var replyError = function(errorCode, message){
    var error = errors[errorCode.toString()];

    message.status = error.code;
    message.payload = error.body;

    reply(message);
  };

  var onMessage = function(){

    var msg;
    var frames = _.toArray(arguments);

    try{

      var from = frames[IDENTITY_FRAME];
      var rid = frames[RID_FRAME];

      log.info("received rid: %s from: %s", rid, from);
      frames = metric.feStart(frames);

      // TODO: log frames in debug mode
      // if (log.isDebug()) {
      //   log.debug(Message.parse(frames).toString());
      // }

      // valid client identity
      if(!from){
        log.error("received message without client identity for rid:", rid);
        msg = Message.parse(frames);
        replyError(500, msg);
        return;
      }

      // execute service name resolution
      var address = msgpack.decode(frames[ADDRESS_FRAME]);
      var to = smiService.getInstance(address.sid);

      // invalid address
      if (to === null) {
        msg = Message.parse(frames);
        // reply with error on invalid address
        log.error("received an invalid address for rid: %s => %j", rid, msg.address);
        replyError(404, msg);
        return;
      }

      log.info("routing rid: %s from: %s to: %s", rid, from, to);

      // append destination identity
      frames.unshift(to);

      instance.backendSendCallback(frames);
    }
    catch(err){
      log.error('terminated on error handling request: ', err.stack);
    }
  };

  var onError = function(error){
    // reply with error
    log.error("received zmq error => %s", error.stack);
  };

  var run = function(){
    log.info('connected to %s', config.frontend);

    frontend = zmq.socket('router');
    frontend.on('message', onMessage);
    frontend.on('error', onError);
    frontend.bindSync(config.frontend);
  };

  var stop = function(){
    log.info('disconnected from %s', config.frontend);
    frontend.close();
  };

  instance = {
    send: replyFrames,
    run:  run,
    stop: stop,
    backendSendCallback: null
  };

  return instance;
};

module.exports = Frontend;