lib/instrumentation/modules/mimic-response.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';

/*
 * This instrumentation exists to work around an issue in mimic-response@1.0.0
 * that was fixed in mimic-response@1.0.1.
 * See https://github.com/elastic/apm-agent-nodejs/issues/423.
 */

var semver = require('semver');

module.exports = function (mimicResponse, agent, { version, enabled }) {
  if (!enabled) return mimicResponse;

  if (semver.gte(version, '1.0.1')) {
    agent.logger.debug(
      "mimic-response version %s doesn't need to be patched - ignoring...",
      version,
    );
    return mimicResponse;
  }

  var ins = agent._instrumentation;

  return function wrappedMimicResponse(fromStream, toStream) {
    // If we bound the `fromStream` emitter, but not the `toStream` emitter, we
    // need to do so as else the `on`, `addListener`, and `prependListener`
    // functions of the `fromStream` will be copied over to the `toStream` but
    // run in the context of the `fromStream`.
    if (
      fromStream &&
      toStream &&
      ins.isEventEmitterBound(fromStream) &&
      !ins.isEventEmitterBound(toStream)
    ) {
      ins.bindEmitter(toStream);
    }
    return mimicResponse.apply(null, arguments);
  };
};