feat: Express middleware tracing integration

kamilogorek · kamilogorek · commit d5b3df60c34f · 2019-11-01T11:28:28.000+01:00
diff --git a/packages/integrations/src/express.ts b/packages/integrations/src/express.ts
@@ -0,0 +1,124 @@
+import { EventProcessor, Hub, Integration } from '@sentry/types';
+import { logger } from '@sentry/utils';
+import { Application, ErrorRequestHandler, NextFunction, Request, RequestHandler, Response } from 'express';
+
+/**
+ * Express integration
+ *
+ * Provides an request and error handler for Express framework
+ * as well as tracing capabilities
+ */
+export class Express implements Integration {
+  /**
+   * @inheritDoc
+   */
+  public name: string = Express.id;
+
+  /**
+   * @inheritDoc
+   */
+  public static id: string = 'Express';
+
+  /**
+   * Express App instance
+   */
+  private readonly _app?: Application;
+
+  /**
+   * @inheritDoc
+   */
+  public constructor(options: { app?: Application } = {}) {
+    this._app = options.app;
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public setupOnce(_addGlobalEventProcessor: (callback: EventProcessor) => void, getCurrentHub: () => Hub): void {
+    if (!this._app) {
+      logger.error('ExpressIntegration is missing an Express instancex');
+      return;
+    }
+    instrumentMiddlewares(this._app, getCurrentHub);
+  }
+}
+
+/**
+ * JSDoc
+ */
+function wrap(fn: Function, getCurrentHub: () => Hub): RequestHandler | ErrorRequestHandler {
+  const arrity = fn.length;
+
+  switch (arrity) {
+    case 2: {
+      return function(this: NodeJS.Global, _req: Request, res: Response): any {
+        const span = getCurrentHub().startSpan({
+          description: fn.name,
+          op: 'middleware',
+        });
+        res.once('finish', () => span.finish());
+        return fn.apply(this, arguments);
+      };
+    }
+    case 3: {
+      return function(this: NodeJS.Global, req: Request, res: Response, next: NextFunction): any {
+        const span = getCurrentHub().startSpan({
+          description: fn.name,
+          op: 'middleware',
+        });
+        fn.call(this, req, res, function(this: NodeJS.Global): any {
+          span.finish();
+          return next.apply(this, arguments);
+        });
+      };
+    }
+    case 4: {
+      return function(this: NodeJS.Global, err: any, req: Request, res: Response, next: NextFunction): any {
+        const span = getCurrentHub().startSpan({
+          description: fn.name,
+          op: 'middleware',
+        });
+        fn.call(this, err, req, res, function(this: NodeJS.Global): any {
+          span.finish();
+          return next.apply(this, arguments);
+        });
+      };
+    }
+    default: {
+      throw new Error(`Express middleware takes 2-4 arguments. Got: ${arrity}`);
+    }
+  }
+}
+
+/**
+ * JSDoc
+ */
+function wrapUseArgs(args: IArguments, getCurrentHub: () => Hub): unknown[] {
+  return Array.from(args).map((arg: unknown) => {
+    if (typeof arg === 'function') {
+      return wrap(arg, getCurrentHub);
+    }
+
+    if (Array.isArray(arg)) {
+      return arg.map((a: unknown) => {
+        if (typeof a === 'function') {
+          return wrap(a, getCurrentHub);
+        }
+        return a;
+      });
+    }
+
+    return arg;
+  });
+}
+
+/**
+ * JSDoc
+ */
+function instrumentMiddlewares(app: Application, getCurrentHub: () => Hub): any {
+  const originalAppUse = app.use;
+  app.use = function(): any {
+    return originalAppUse.apply(this, wrapUseArgs(arguments, getCurrentHub));
+  };
+  return app;
+}
