heartbeat.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

const
urlparse = require('urlparse'),
logger = require('./logging.js').logger,
url = require('url');

// the path that heartbeats live at
exports.path = '/__heartbeat__';

// a helper function to set up a heartbeat check
exports.setup = function(app, options, cb) {
  var dependencies = [];

  if (typeof options == 'function') {
    cb = options;
  } else if (options) {
    dependencies = options.dependencies;
  }
  var count = dependencies.length;

  app.use(function(req, res, next) {
    if (req.method === 'GET' && req.path === exports.path) {
      var checked = 0;
      var query = url.parse(req.url, true).query;
      var deep = typeof query.deep != 'undefined';
      var notOk = [];

      // callback for checking a dependency
      function checkCB (num) {
        return function (isOk) {
          checked++;
          if (!isOk) {
            notOk.push(dependencies[num]);
          }

          // if all dependencies have been checked
          if (checked == count) {
            if (notOk.length === 0) {
              try {
                if (cb) cb(ok);
                else ok(true);
              } catch(e) {
                logger.error("Exception caught in heartbeat handler: " + e.toString());
                ok(false, e);
              }
            } else {
                logger.error("Not all dependencies available");
                ok(false, notOk.join(': failed\n') + ': failed');
            }
          }
        };
      }

      function ok(yeah, msg) {
        res.writeHead(yeah ? 200 : 500);
        res.write(yeah ? 'ok' : 'bad');
        if (msg) res.write(msg);
        res.end();
      }

      // check all dependencies if deep
      if (deep) {
        for (var i = 0; i < count; i++) {
          check(dependencies[i] + exports.path, checkCB(i));
        }
      } else {
        try {
          if (cb) cb(ok);
          else ok(true);
        } catch(e) {
          logger.error("Exception caught in heartbeat handler: " + e.toString());
          ok(false);
        }
      }
    } else {
      return next();
    }
  });
};


// a function to check the heartbeat of a remote server
var check = exports.check = function(url, cb) {
  if (typeof url === 'string') url = urlparse(url).normalize().validate();
  else if (typeof url !== 'object') throw "url string or object required as argumnet to heartbeat.check";
  if (!url.port) url.port = (url.scheme === 'http') ? 80 : 443;

  var shortname = url.host + ':' + url.port;

  require(url.scheme).get({
    host: url.host,
    port: url.port,
    path: exports.path
  }, function (res) {
    if (res.statusCode === 200) cb(true);
    else logger.error("non-200 response from " + shortname + ".  fatal! (" + res.statusCode + ")");
  }, function (e) {
    logger.error("can't communicate with " + shortname + ".  fatal: " + e);
    cb(false);
  });
};