Feature/add metrics type summary (#24)

* add metric type summary

* add tests for percentile option

* throw errors for unknown metricType

* set histogram as default metrics type

README.md

@@ -9,7 +9,7 @@ Internally it uses **prom-client**. See: https://github.com/siimon/prom-client
 Included metrics:
 
 * `up`: normally is just 1
-* `http_request_duration_seconds`: http latency histogram labeled with `status_code`, `method` and `path`
+* `http_request_duration_seconds`: http latency histogram/summary labeled with `status_code`, `method` and `path`
 
 ## Install
 
@@ -64,6 +64,12 @@ The code the master process runs will expose an API with a single endpoint `/clu
 
 ## Options
 
+Metrics type:
+
+* **metricsType**: two metrics type are supported for `http_request_duration_seconds` metric: [histogram](https://prometheus.io/docs/concepts/metric_types/#histogram) and [summary](https://prometheus.io/docs/concepts/metric_types/#summary),  default: **histogram**
+
+
+
 Which labels to include in `http_request_duration_seconds` metric:
 
 * **includeStatusCode**: HTTP status code (200, 400, 404 etc.), default: **true**
@@ -87,6 +93,7 @@ Extra transformation callbacks:
 Other options:
 
 * **buckets**: buckets used for `http_request_duration_seconds` histogram
+* **percentiles**: percentiles used for `http_request_duration_seconds` summary
 * **autoregister**: if `/metrics` endpoint should be registered. (Default: **true**)
 * **promClient**: options for promClient startup, e.g. **collectDefaultMetrics**. This option was added
   to keep `express-prom-bundle` runnable using confit (e.g. with kraken.js) without writing any JS code,

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "express-prom-bundle",
-  "version": "4.1.0",
+  "version": "4.2.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {

spec/index.spec.js

@@ -186,6 +186,54 @@ describe('index', () => {
       });
   });
 
+  it('metrics type summary works', done => {
+    const app = express();
+    const bundled = bundle({
+      metricsType: 'summary',
+      percentiles: [0.5, 0.85, 0.99],
+    });
+    app.use(bundled);
+    app.use('/test', (req, res) => res.send('it worked'));
+
+    const agent = supertest(app);
+    agent.get('/test').end(() => {
+      agent
+        .get('/metrics')
+        .end((err, res) => {
+          expect(res.status).toBe(200);
+          expect(res.text).toMatch(/quantile="0.85"/);
+          done();
+        });
+    });
+  });
+
+  it('metrics type histogram works', done => {
+    const app = express();
+    const bundled = bundle({
+      metricsType: 'histogram',
+      buckets: [10, 100],
+    });
+    app.use(bundled);
+    app.use('/test', (req, res) => res.send('it worked'));
+
+    const agent = supertest(app);
+    agent.get('/test').end(() => {
+      agent
+        .get('/metrics')
+        .end((err, res) => {
+          expect(res.status).toBe(200);
+          expect(res.text).toMatch(/le="100"/);
+          done();
+        });
+    });
+  });
+
+  it('throws on unknown metricType ', () => {
+    expect(() => {
+      bundle({metricsType: 'hello',});
+    }).toThrow();
+  });
+
   describe('usage of normalizePath()', () => {
 
     it('normalizePath can be replaced gloablly', done => {

src/index.js

@@ -62,6 +62,7 @@ function main(opts) {
       includeStatusCode: true,
       normalizePath: main.normalizePath,
       formatStatusCode: main.normalizeStatusCode,
+      metricsType: 'histogram',
       promClient: {}
     },
     opts
@@ -106,13 +107,24 @@ function main(opts) {
       if (opts.customLabels){
         labels.push.apply(labels, Object.keys(opts.customLabels));
       }
-      const metric = new promClient.Histogram({
-        name: httpMetricName,
-        help: 'duration histogram of http responses labeled with: ' + labels.join(', '),
-        labelNames: labels,
-        buckets: opts.buckets || [0.003, 0.03, 0.1, 0.3, 1.5, 10]
-      });
-      return metric;
+
+      if (opts.metricsType === 'summary') {
+        return new promClient.Summary({
+          name: httpMetricName,
+          help: 'duration summary of http responses labeled with: ' + labels.join(', '),
+          labelNames: labels,
+          percentiles: opts.percentiles || [0.5, 0.75, 0.95, 0.98, 0.99, 0.999]
+        });
+       } else if (opts.metricsType === 'histogram' || !opts.metricsType) {
+        return new promClient.Histogram({
+          name: httpMetricName,
+          help: 'duration histogram of http responses labeled with: ' + labels.join(', '),
+          labelNames: labels,
+          buckets: opts.buckets || [0.003, 0.03, 0.1, 0.3, 1.5, 10]
+        });
+      } else {
+        throw new Error('metricsType option must be histogram or summary');
+      }
     }
   };