iot-sol/node_modules/hope-center/lib/heartbeat_server.js

Intel(r) IoT Services Orchestration Layer - HTML5 IDE + Node.js middleware to create and host distributed IoT Apps in minutes

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var B = require("hope-base");
var _ = require("lodash");
var log = B.log.for_category("heartbeat");
var P = require("hope-hub-center-shared").protocol;

var HeartBeatServer =
/**
 * HeartBeat Server
 * @param  {Object} config {
 *  store: ...,           // a store for info of heartbeat only
 *                        // put it in a seperated store other than em 
 *                        // as these are very volatile info.
 *  
 *  check_interval: ...   // how frequently to check whether hub is dropped
 *
 *  drop_threshold: ...   // consider a hub as dropped if hasn't received update
 *                        // for such long
 *  
 * }
 * @return {HeartBeatServer}       
 */
module.exports = function(center, config) {
  this.center = center;
  config = config || {};
  B.check(_.isObject(config.store), "heartbeat", "Need a store for heartbeat server"); 
  this.store = config.store;
  this.check_interval = config.check_interval || 1000 * 60 * 2;
  this.drop_threshold = config.drop_threshold || 3 * this.check_interval + 1;
  this.check_timer = null;
  this.check_func = this.check.bind(this);
};

HeartBeatServer.prototype.enable = function() {
  var self = this;
  if (!this.check_timer) {
    log("enabled");
    this.check_timer = setInterval(this.check_func, this.check_interval);
    this.center.mnode.subscribe_all$(P.HEARTBEAT, function(hb) {
      self.heard_from_hub$(hb).done();
    });
  }
};

HeartBeatServer.prototype.disable = function() {
  if (this.check_timer) {
    log("disabled");
    clearInterval(this.check_timer);
    this.center.mnode.unsubscribe_all$(P.HEARTBEAT);
    this.check_timer = null;
  }
};

// item in store contains {
//   id: the hub id
//   timestamp: last time it gets heatbeat akin
// }

HeartBeatServer.prototype.check = function() {
  var self = this;
  var time = Date.now();
  this.store.list$().then(function(ids) {
    return self.store.batch_get$(ids).then(function(items) {
      items.forEach(function(item) {
        if (time - item.timestamp > self.drop_threshold) {
          log.warn("LEAVE", item.id);
          self.center.force_hub_leave(item.id);
          self.leave$(item.id);
        }
      });
    });
  }).catch(function(err) {
    log.error("check", err);
  }).done();
};

// hb in format of {
//   id: the hub id
//   em_timestamp: the timestamp of hub and it's an array (i.e. hrtime)
//   mnode_id
// }
HeartBeatServer.prototype.heard_from_hub$ = function(hb) {
  log("heard from hub", hb);
  var self = this;
  return self.center.em.hub_store.get$(hb.id)
  .then(function(hub) {
    if (_.isUndefined(hub)) {
      log("hub not exist before", hb);
      return self.center.mnode.send$(hb.mnode_id, P.NEED_EM_FULLINFO, self.center.get_info());
    }
    else if (timestamp_match(hb.em_timestamp, hub.timestamp)) {
      log("hearbeat match", hb);
      return self.beat$(hb.id);
    }
    else if (timestamp_ahead(hb.em_timestamp, hub.timestamp)) {
      log("hearbeat ahead", hb);
      return self.center.mnode.send$(hb.mnode_id, P.NEED_EM_FULLINFO, self.center.get_info())
      .then(function() {
        return self.beat$(hb.id);
      });
    }
    else if (timestamp_old(hb.em_timestamp, hub.timestamp)) {
      log("hearbeat old, ignore", hb);
      return;
    }
    else {
      B.check(false, "heartbeat", "should not run here"); 
    }
  });
};

HeartBeatServer.prototype.beat$ = function(hub_id) {
  log("beat", hub_id);
  var time = Date.now();
  var self = this;
  return this.store.make_lock(hub_id).lock_as_promise$(function() {
    return self.store.set$(hub_id, {
      id: hub_id,
      timestamp: time
    });
  });
};

HeartBeatServer.prototype.leave$ = function(hub_id) {
  var self = this;
  return this.store.make_lock(hub_id).lock_as_promise$(function() {
    return self.store.delete$(hub_id);
  });

};

function timestamp_match(comming, existing) {
  return B.time.compare_hrtime(comming.now, existing.now) === 0 &&
         B.time.compare_hrtime(comming.last, existing.last) === 0;
}

function timestamp_ahead(comming, existing) {
  return B.time.compare_hrtime(comming.now, existing.now) === 1;
}

function timestamp_old(comming, existing) {
  return B.time.compare_hrtime(comming.now, existing.now) === -1;
}