From c918b44c2b7bb1010daa25c22dce7831c3bc5c47 Mon Sep 17 00:00:00 2001
From: Konstantin Pogorelov <or@pluseq.com>
Date: Thu, 1 Dec 2016 00:28:45 +0100
Subject: [PATCH] minor dep. upgrade, do not remove initial metrics if they
 match the requested prefix (i.e. recognized as own metrics), bump 1.2.2

---
 package.json      | 10 +++++-----
 spec/indexSpec.js | 34 ++++++++++++++++++++++++++++++++++
 src/index.js      | 10 ++++++++--
 3 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/package.json b/package.json
index f13169f..2a1c383 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "express-prom-bundle",
-  "version": "1.2.1",
+  "version": "1.2.2",
   "description": "express middleware with popular prometheus metrics in one bundle",
   "main": "src/index.js",
   "keywords": [
@@ -20,10 +20,10 @@
     "url-value-parser": "^1.0.0"
   },
   "devDependencies": {
-    "coveralls": "^2.11.12",
-    "eslint": "^3.11.0",
-    "express": "^4.13.4",
-    "istanbul": "^0.4.4",
+    "coveralls": "^2.11.15",
+    "eslint": "^3.11.1",
+    "express": "^4.14.0",
+    "istanbul": "^0.4.5",
     "jasme": "^5.2.0",
     "koa": "^1.2.4",
     "koa-connect": "^1.0.0",
diff --git a/spec/indexSpec.js b/spec/indexSpec.js
index 8e8bf3a..4a6ce7f 100644
--- a/spec/indexSpec.js
+++ b/spec/indexSpec.js
@@ -9,6 +9,17 @@ const c2k = require("koa-connect");
 const supertestKoa = require("supertest-koa-agent");
 const promClient = require("prom-client");
 
+// had to reinvent, because getSingleMetric() is still not in npm
+function myGetSingleMetric(name) {
+    let returnMetric;
+    promClient.register.getMetricsAsJSON().forEach(metric => {
+        if (metric.name === name) {
+            returnMetric = metric;
+        }
+    });
+    return returnMetric;
+}
+
 describe("index", () => {
     beforeEach(() => {
         promClient.register.clear();
@@ -146,6 +157,29 @@ describe("index", () => {
             });
     });
 
+    describe("initial metrics removal", () => {
+        it("removes unexpected metrics on start with no prefix", () => {
+            new promClient.Counter("foo", "bar");
+            expect(myGetSingleMetric("foo")).toBeDefined();
+            bundle();
+            expect(myGetSingleMetric("foo")).not.toBeDefined();
+        });
+
+        it("removes unexpected metrics on start with a prefix", () => {
+            new promClient.Counter("foo", "bar");
+            expect(myGetSingleMetric("foo")).toBeDefined();
+            bundle({prefix: "some_test_"});
+            expect(myGetSingleMetric("foo")).not.toBeDefined();
+        });
+
+        it("doesnt remove metrics with matched prefix", () => {
+            new promClient.Counter("some_test_foo", "bar");
+            expect(myGetSingleMetric("some_test_foo")).toBeDefined();
+            bundle({prefix: "some_test_"});
+            expect(myGetSingleMetric("some_test_foo")).toBeDefined();
+        });
+    });
+
     it("tolerates includePath, includeMethod and keepDefaultMetrics", done => {
         const app = express();
         const instance = bundle({
diff --git a/src/index.js b/src/index.js
index c30a4b3..22fbf64 100644
--- a/src/index.js
+++ b/src/index.js
@@ -51,10 +51,16 @@ function main(opts) {
         return;
     }
 
-    // remove default metrics provided by prom-client
+    // this is a really messy hack but needed for compatibility with v1
+    // will be completely removed in v2
     if (!opts.keepDefaultMetrics) {
+        const metrics = promClient.register.getMetricsAsJSON();
         clearInterval(promClient.defaultMetrics());
-        promClient.register.clear();
+        metrics.forEach(metric => {
+            if (!opts.prefix || metric.name.substr(0, opts.prefix.length) != opts.prefix) {
+                promClient.register.removeSingleMetric(metric.name);
+            }
+        });
     }
 
     const factory = new PromFactory(opts);