changed wording + added doc + unit test

README.md

@@ -52,7 +52,7 @@ Which labels to include in `http_request_duration_seconds` metric:
 * **includeUp**: include an auxiliary "up"-metric which always returns 1, default: **true**
 * **metricsPath**: replace the `/metrics` route with a **regex** or exact **string**. Note: it is highly recommended to just stick to the default
 * **metricType**: histogram/summary selection. See more details below
-* **filter**: whether the incoming request should be included in the metrics
+* **bypass**: Function which takes express request as an argument. Determines whether the given request should be included in the metrics or not, default: **() => false**
 
 ### metricType option ###
 

spec/index.spec.js

@@ -200,6 +200,36 @@ describe('index', () => {
       });
   });
 
+  it('bypass requests', done => {
+    const app = express();
+    const instance = bundle({
+      bypass: (req)=> {
+        return ['/test', /bad.word/].includes(req.url)
+      }
+    });
+    app.use(instance);
+    app.use('/test', (req, res) => res.send('it worked'));
+    app.use('/some/bad-word', (req, res) => res.send('it worked too'));
+    const agent = supertest(app);
+    agent
+      .get('/test')
+      .end(() => {
+        agent
+          .get('/some/bad-word')
+          .end(() => {
+            const metricHashMap = instance.metrics.http_request_duration_seconds.hashMap;
+            expect(metricHashMap['status_code:200']).not.toBeDefined();
+
+            agent
+              .get('/metrics')
+              .end((err, res) => {
+                expect(res.status).toBe(200);
+                done();
+              });
+          });
+      });
+  });
+
   it('complains about deprecated options', () => {
     expect(() => bundle({prefix: 'hello'})).toThrow();
   });

src/index.js

@@ -131,7 +131,7 @@ function main(opts) {
     : new RegExp('^' + (opts.metricsPath || '/metrics') + '/?$');
 
   const middleware = function (req, res, next) {
-    if (opts.filter && opts.filter(req)) {
+    if (opts.bypass && opts.bypass(req)) {
       return next();
     }
 

types/index.d.ts

@@ -28,7 +28,7 @@ declare namespace express_prom_bundle {
     includePath?: boolean;
     includeUp?: boolean;
 
-    filter?: (req: Request) => boolean;
+    bypass?: (req: Request) => boolean;
 
     metricType?: 'summary' | 'histogram';
     metricsPath?: string;