From 0ce44722a5b0d1ed9734fb0cbceff2cee1c22bbd Mon Sep 17 00:00:00 2001
From: Konstantin Pogorelov <kp@pvradar.com>
Date: Sat, 6 Jan 2024 10:48:57 +0100
Subject: [PATCH] use collectDefaultMetrics.prefix for up metric

---
 spec/index.spec.js | 36 +++++++++++++++++++++++++++++-------
 src/index.js       |  6 +++++-
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/spec/index.spec.js b/spec/index.spec.js
index 665850c..193e4b9 100644
--- a/spec/index.spec.js
+++ b/spec/index.spec.js
@@ -546,15 +546,37 @@ describe('index', () => {
     });
   });
 
-  it('calls promClient.collectDefaultMetrics', () => {
-    const spy = spyOn(promClient, 'collectDefaultMetrics');
-    bundle({
-      promClient: {
-        collectDefaultMetrics: {
+  describe('option collectDefaultMetrics', () => {
+    it('it gets called', () => {
+      const spy = spyOn(promClient, 'collectDefaultMetrics');
+      bundle({
+        promClient: {
+          collectDefaultMetrics: {
+          }
         }
-      }
+      });
+      expect(spy).toHaveBeenCalledWith({});
+    });
+
+    it('prefix is used for up metric', (done) => {
+      const instance = bundle({
+        promClient: {
+          collectDefaultMetrics: {
+            prefix: 'hello_'
+          }
+        }
+      });
+      const app = express();
+      app.use(instance);
+      const agent = supertest(app);
+      agent
+        .get('/metrics')
+        .end((err, res) => {
+          expect(res.status).toBe(200);
+          expect(res.text).toMatch(/^hello_up\s1/m);
+          done();
+        });
     });
-    expect(spy).toHaveBeenCalledWith({});
   });
 
   describe('usage of clusterMetrics()', () => {
diff --git a/src/index.js b/src/index.js
index 0c96dfb..187de0d 100644
--- a/src/index.js
+++ b/src/index.js
@@ -132,8 +132,12 @@ function main(opts) {
   };
 
   if (opts.includeUp !== false) {
+    let prefix = '';
+    if (opts.promClient && opts.promClient.collectDefaultMetrics) {
+      prefix = opts.promClient.collectDefaultMetrics.prefix || '';
+    }
     metrics.up = new promClient.Gauge({
-      name: 'up',
+      name: `${prefix}up`,
       help: '1 = up, 0 = not up',
       registers: [opts.promRegistry]
     });