src/plugins/ExpressPlugin.ts

/*!
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

import SwPlugin from '../core/SwPlugin';
import { IncomingMessage, ServerResponse } from 'http';
import ContextManager from '../trace/context/ContextManager';
import { Component } from '../trace/Component';
import Tag from '../Tag';
import { ContextCarrier } from '../trace/context/ContextCarrier';
import DummySpan from '../trace/span/DummySpan';
import { ignoreHttpMethodCheck } from '../config/AgentConfig';
import PluginInstaller from '../core/PluginInstaller';
import HttpPlugin from './HttpPlugin';

class ExpressPlugin implements SwPlugin {
  readonly module = 'express';
  readonly versions = '*';

  install(installer: PluginInstaller): void {
    this.interceptServerRequest(installer);
  }

  private interceptServerRequest(installer: PluginInstaller) {
    const router = installer.require('express/lib/router');
    const _handle = router.handle;

    router.handle = function(req: IncomingMessage, res: ServerResponse, next: any) {
      const carrier = ContextCarrier.from((req as any).headers || {});
      const operation = (req.url || '/').replace(/\?.*/g, '');
      const span = ignoreHttpMethodCheck(req.method ?? 'GET')
        ? DummySpan.create()
        : ContextManager.current.newEntrySpan(operation, carrier, Component.HTTP_SERVER);

      span.component = Component.EXPRESS;

      if (span.depth)  // if we inherited from http then just change component ID and let http do the work
        return _handle.apply(this, arguments);

      return HttpPlugin.wrapHttpResponse(span, req, res, () => {  // http plugin disabled, we use its mechanism anyway
        try {
          return _handle.call(this, req, res, (err: Error) => {
            span.error(err);
            next.call(this, err);
          });

        } finally {  // req.protocol is only possibly available after call to _handle()
          span.tag(Tag.httpURL(((req as any).protocol ? (req as any).protocol + '://' : '') + (req.headers.host || '') + req.url));
        }
      });
    };
  }
}

// noinspection JSUnusedGlobalSymbols
export default new ExpressPlugin();