lib/instrumentation/modules/finalhandler.js

/*
 * Copyright Elasticsearch B.V. and other contributors where applicable.
 * Licensed under the BSD 2-Clause License; you may not use this file except in
 * compliance with the BSD 2-Clause License.
 */

'use strict';

// Instrumentation of https://www.npmjs.com/package/finalhandler
// This will `apm.captureError` any error passed to the finalhandler.
//
// Both 'express' and 'connect' use finalhandler, so this effectively handles
// capturing errors from incoming request handlers for Express and Connect apps.
// The `errorReportedSymbol` symbol is used to coordinate with 'express'
// instrumentation to avoid double-reporting errors.

var isError = require('core-util-is').isError;

var symbols = require('../../symbols');

function shouldReport(err) {
  if (typeof err === 'string') return true;
  if (isError(err) && !err[symbols.errorReportedSymbol]) {
    err[symbols.errorReportedSymbol] = true;
    return true;
  }
  return false;
}

module.exports = function (finalhandler, agent) {
  return function wrappedFinalhandler(req, res, options) {
    var final = finalhandler.apply(this, arguments);

    return function (err) {
      if (shouldReport(err)) {
        agent.captureError(err, { request: req });
      }
      return final.apply(this, arguments);
    };
  };
};