ability to exclude incoming request from metrics

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
 
 ### metricType option ###
 

src/index.js

@@ -131,6 +131,10 @@ function main(opts) {
     : new RegExp('^' + (opts.metricsPath || '/metrics') + '/?$');
 
   const middleware = function (req, res, next) {
+    if (opts.filter && opts.filter(req)) {
+      return next();
+    }
+
     const path = req.originalUrl || req.url; // originalUrl gets lost in koa-connect?
 
     if (opts.autoregister && path.match(metricsMatch)) {

types/index.d.ts

@@ -28,6 +28,8 @@ declare namespace express_prom_bundle {
     includePath?: boolean;
     includeUp?: boolean;
 
+    filter?: (req: Request) => boolean;
+
     metricType?: 'summary' | 'histogram';
     metricsPath?: string;
     httpDurationMetricName?: string;