deep-framework/vendor/aws-xray-sdk/lib/middleware/express_mw.js

DEEP Framework

/**
 * Express middleware module.
 *
 * Exposes Express middleware functions to enable automated data capturing on a web service. To enable on a Node.js/Express application,
 * use 'app.use(AWSXRay.express.openSegment())' before defining your routes.  After your routes, before any extra error
 * handling middleware, use 'app.use(AWSXRay.express.closeSegment())'.
 * Use AWSXRay.getSegment() to access the current segment/subsegment.
 * Otherwise, for manual mode, this appends the Segment object to the request object as req.segment.
 * @module express_mw
 */

var CLSUtils = require('../utils').CLSUtils;
var MWUtils = require('./mw_utils');
var Local = require('../segments/attributes/local');
var Segment = require('../segments/segment');
var getCauseType = require('../utils').getCauseTypeFromHttpStatus;

/**
 * Use 'app.use(AWSXRay.express.openSegment('defaultName'))' before defining your routes.
 * Use AWSXRay.getSegment() to access the current segment/subsegment.
 * Otherwise, for manual mode, this appends the Segment object to the request object as req.segment.
 * @param {string} defaultName - The default name for the segment.
 * @alias module:express_mw.openSegment
 * @returns {function}
 */

module.exports.openSegment = function openSegment(defaultName) {
  if (!defaultName || typeof defaultName !== 'string')
    throw new Error('Default segment name was not supplied.  Please provide a string.');

  MWUtils.setDefaultName(defaultName);

  return function open(req, res, next) {
    var amznTraceHeader = MWUtils.processHeaders(req);
    var name = MWUtils.resolveName(req.headers.host);
    var segment = new Segment(name, amznTraceHeader.Root, amznTraceHeader.Parent);

    MWUtils.resolveSampling(amznTraceHeader, segment, res);
    segment.addAttribute('http', new Local(req));

    res.on('finish', function () {
      if (this.statusCode === 429)
        segment.addThrottle();
      else if (getCauseType(this.statusCode))
        segment[getCauseType(this.statusCode)] = true;

      segment.http.close(this);
      segment.close();
    });

    if (CLSUtils.isCLSMode()) {
      var ns = CLSUtils.getNamespace();
      ns.bindEmitter(req);
      ns.bindEmitter(res);

      ns.run(function () {
        CLSUtils.setSegment(segment);
        if (next) { next(); }
      });
    } else {
      req.segment = segment;
      if (next) { next(); }
    }
  };
};

/**
 * After your routes, before any extra error handling middleware, use 'app.use(AWSXRay.express.closeSegment())'.
 * @alias module:express_mw.closeSegment
 * @returns {function}
 */

module.exports.closeSegment = function closeSegment() {
  return function close(err, req, res, next) {
    var segment = CLSUtils.isCLSMode() ? CLSUtils.getSegment() : req.segment;

    if (segment && err) {
      segment.close(err);
    } else if (segment) {
      segment.close();
    }

    if (next)
      next(err);
  };
};