version 2.2.0 - normalizeStatus draft

package.json

@@ -1,6 +1,6 @@
 {
   "name": "express-prom-bundle",
-  "version": "2.1.0",
+  "version": "2.2.0",
   "description": "express middleware with popular prometheus metrics in one bundle",
   "main": "src/index.js",
   "keywords": [

spec/normalizeStatusCode.spec.js

@@ -0,0 +1,23 @@
+'use strict';
+/* eslint-env jasmine */
+
+const normalizeStatusCode = require('../src/normalizeStatusCode');
+
+describe('normalizeStatusCode', () => {
+  it('returns original if disabled in opts', () => {
+    expect(
+     normalizeStatusCode({status_code: 404}, {normalizeStatusCode: false})
+   ).toBe(404);
+  });
+
+  it('returns run callback if configured', () => {
+    expect(
+      normalizeStatusCode(
+        {status_code: 500},
+        {
+          formatStatusCode: res => String(res.status_code).slice(0, -2) + 'xx'
+        }
+      )
+    ).toBe('5xx');
+  });
+});

src/index.js

@@ -2,6 +2,7 @@
 const onFinished = require('on-finished');
 const promClient = require('prom-client');
 const normalizePath = require('./normalizePath');
+const normalizeStatusCode = require('./normalizeStatusCode');
 
 function matchVsRegExps(element, regexps) {
   for (let regexp of regexps) {
@@ -116,7 +117,12 @@ function main(opts) {
       labels = {'status_code': 0};
       let timer = metrics[httpMtricName].startTimer(labels);
       onFinished(res, () => {
-        labels.status_code = res.statusCode;
+        if (opts.normalizeStatusCode) {
+          labels.status_code = main.normalizeStatusCode(res, opts);
+        } else {
+          labels.status_code = res.statusCode;
+        }
+
         if (opts.includeMethod) {
           labels.method = req.method;
         }
@@ -139,4 +145,5 @@ function main(opts) {
 
 main.promClient = promClient;
 main.normalizePath = normalizePath;
+main.normalizeStatusCode = normalizeStatusCode;
 module.exports = main;

src/normalizePath.js

@@ -24,4 +24,3 @@ module.exports = function(req, opts) {
   }
   return urlValueParser.replacePathValues(path);
 };
-

src/normalizeStatusCode.js

@@ -0,0 +1,11 @@
+'use strict';
+
+module.exports = function(res, opts) {
+  opts = opts || {};
+
+  if (typeof opts.formatStatusCode === 'function') {
+    return opts.formatStatusCode(res, opts);
+  }
+
+  return res.status_code;
+};