Add resource usage metrics for middleware

See
https://prometheus.io/docs/instrumenting/writing_clientlibs/#standard-and-runtime-collectors

.changeset/tough-jokes-cheer.md

@@ -0,0 +1,5 @@
+---
+"@vue-storefront/middleware": minor
+---
+
+[ADDED] It is now possible to access Prometheus metrics by querying the /metrics path (e.g. GET http://localhost:4000/metrics)

packages/middleware/package.json

@@ -24,7 +24,8 @@
     "cookie-parser": "^1.4.6",
     "cors": "^2.8.5",
     "express": "^4.18.1",
-    "helmet": "^5.1.1"
+    "helmet": "^5.1.1",
+    "prom-client": "^15.1.3"
   },
   "devDependencies": {
     "@types/body-parser": "^1.19.2",

packages/middleware/src/createServer.ts

@@ -18,6 +18,7 @@ import {
   prepareArguments,
   callApiFunction,
 } from "./handlers";
+import { createPrometheusMetricsHandler } from "./helpers/metrics";
 
 const defaultCorsOptions: CreateServerOptions["cors"] = {
   credentials: true,
@@ -82,6 +83,8 @@ async function createServer<
     res.end("ok");
   });
 
+  app.get("/metrics", createPrometheusMetricsHandler());
+
   consola.success("Middleware created!");
   return app;
 }

packages/middleware/src/helpers/metrics.ts

@@ -0,0 +1,15 @@
+import { RequestHandler } from "express";
+import Prometheus from "prom-client";
+
+export const createPrometheusMetricsHandler: () => RequestHandler = () => {
+  const register = new Prometheus.Registry();
+  register.setDefaultLabels({
+    app: "middleware",
+  });
+  Prometheus.collectDefaultMetrics({ register });
+
+  return async (_, res) => {
+    res.contentType(register.contentType);
+    res.end(await register.metrics());
+  };
+};

yarn.lock

@@ -3635,6 +3635,11 @@
   resolved "https://registry.yarnpkg.com/@opentelemetry/api/-/api-1.8.0.tgz#5aa7abb48f23f693068ed2999ae627d2f7d902ec"
   integrity sha512-I/s6F7yKUDdtMsoBWXJe8Qz40Tui5vsuKCWJEWVL+5q9sSWRzzx6v2KeNsOBEwd94j0eWkpWCH4yB6rZg9Mf0w==
 
+"@opentelemetry/api@^1.4.0":
+  version "1.9.0"
+  resolved "https://registry.yarnpkg.com/@opentelemetry/api/-/api-1.9.0.tgz#d03eba68273dc0f7509e2a3d5cba21eae10379fe"
+  integrity sha512-3giAOQvZiH5F9bMlMiv8+GSPMeqg0dbaeo58/0SlA9sxSqZhnUtxzX9/2FzyhS9sWQf5S0GJE0AKBrFqjpeYcg==
+
 "@opentelemetry/[email protected]":
   version "1.23.0"
   resolved "https://registry.yarnpkg.com/@opentelemetry/core/-/core-1.23.0.tgz#f2e7ada7f35750f3c1674aef1e52c879005c0731"
@@ -6936,6 +6941,11 @@ bindings@^1.4.0:
   dependencies:
     file-uri-to-path "1.0.0"
 
+[email protected]:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/bintrees/-/bintrees-1.0.2.tgz#49f896d6e858a4a499df85c38fb399b9aff840f8"
+  integrity sha512-VOMgTMwjAaUG580SXn3LacVgjurrbMme7ZZNYGSSV7mmtY6QQRh0Eg3pwIcntQ77DErK1L0NxkbetjcoXzVwKw==
+
 birpc@^0.2.17:
   version "0.2.17"
   resolved "https://registry.yarnpkg.com/birpc/-/birpc-0.2.17.tgz#d0bdb90d4d063061156637f03b7b0adea1779734"
@@ -16826,6 +16836,14 @@ process@^0.11.10:
   resolved "https://registry.yarnpkg.com/process/-/process-0.11.10.tgz#7332300e840161bda3e69a1d1d91a7d4bc16f182"
   integrity sha512-cdGef/drWFoydD1JsMzuFf8100nZl+GT+yacc2bEced5f9Rjk4z+WtFUTBu9PhOi9j/jfmBPu0mMEY4wIdAF8A==
 
+prom-client@^15.1.3:
+  version "15.1.3"
+  resolved "https://registry.yarnpkg.com/prom-client/-/prom-client-15.1.3.tgz#69fa8de93a88bc9783173db5f758dc1c69fa8fc2"
+  integrity sha512-6ZiOBfCywsD4k1BN9IX0uZhF+tJkV8q8llP64G5Hajs4JOeVLPCwpPVcpXy3BwYiUGgyJzsJJQeOIv7+hDSq8g==
+  dependencies:
+    "@opentelemetry/api" "^1.4.0"
+    tdigest "^0.1.1"
+
 promise-all-reject-late@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/promise-all-reject-late/-/promise-all-reject-late-1.0.1.tgz#f8ebf13483e5ca91ad809ccc2fcf25f26f8643c2"
@@ -18469,7 +18487,16 @@ string-length@^4.0.1:
     char-regex "^1.0.2"
     strip-ansi "^6.0.0"
 
-"string-width-cjs@npm:string-width@^4.2.0", "string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.0.0, string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.3:
+"string-width-cjs@npm:string-width@^4.2.0":
+  version "4.2.3"
+  resolved "https://registry.yarnpkg.com/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
+  integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
+  dependencies:
+    emoji-regex "^8.0.0"
+    is-fullwidth-code-point "^3.0.0"
+    strip-ansi "^6.0.1"
+
+"string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.0.0, string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.3:
   version "4.2.3"
   resolved "https://registry.yarnpkg.com/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
   integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
@@ -18592,7 +18619,7 @@ string_decoder@~1.1.1:
   dependencies:
     safe-buffer "~5.1.0"
 
-"strip-ansi-cjs@npm:strip-ansi@^6.0.1", strip-ansi@^6.0.0, strip-ansi@^6.0.1:
+"strip-ansi-cjs@npm:strip-ansi@^6.0.1":
   version "6.0.1"
   resolved "https://registry.yarnpkg.com/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
   integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
@@ -18606,6 +18633,13 @@ strip-ansi@^3.0.0:
   dependencies:
     ansi-regex "^2.0.0"
 
+strip-ansi@^6.0.0, strip-ansi@^6.0.1:
+  version "6.0.1"
+  resolved "https://registry.yarnpkg.com/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
+  integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
+  dependencies:
+    ansi-regex "^5.0.1"
+
 strip-ansi@^7.0.1:
   version "7.1.0"
   resolved "https://registry.yarnpkg.com/strip-ansi/-/strip-ansi-7.1.0.tgz#d5b6568ca689d8561370b0707685d22434faff45"
@@ -18906,6 +18940,13 @@ tar@^6.0.2, tar@^6.1.0, tar@^6.1.11, tar@^6.1.2, tar@^6.2.0:
     mkdirp "^1.0.3"
     yallist "^4.0.0"
 
+tdigest@^0.1.1:
+  version "0.1.2"
+  resolved "https://registry.yarnpkg.com/tdigest/-/tdigest-0.1.2.tgz#96c64bac4ff10746b910b0e23b515794e12faced"
+  integrity sha512-+G0LLgjjo9BZX2MfdvPfH+MKLCrxlXSYec5DaPYP1fe6Iyhf0/fSmJ0bFiZ1F8BT6cGXl2LpltQptzjXKWEkKA==
+  dependencies:
+    bintrees "1.0.2"
+
 [email protected]:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/temp-dir/-/temp-dir-1.0.0.tgz#0a7c0ea26d3a39afa7e0ebea9c1fc0bc4daa011d"
@@ -20657,7 +20698,7 @@ wordwrap@^1.0.0:
   resolved "https://registry.yarnpkg.com/wordwrap/-/wordwrap-1.0.0.tgz#27584810891456a4171c8d0226441ade90cbcaeb"
   integrity sha512-gvVzJFlPycKc5dZN4yPkP8w7Dc37BtP1yczEneOb4uq34pXZcvrtRTmWV8W+Ume+XCxKgbjM+nevkyFPMybd4Q==
 
-"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0", wrap-ansi@^7.0.0:
+"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0":
   version "7.0.0"
   resolved "https://registry.yarnpkg.com/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
   integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
@@ -20675,6 +20716,15 @@ wrap-ansi@^6.0.1, wrap-ansi@^6.2.0:
     string-width "^4.1.0"
     strip-ansi "^6.0.0"
 
+wrap-ansi@^7.0.0:
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
+  integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
+  dependencies:
+    ansi-styles "^4.0.0"
+    string-width "^4.1.0"
+    strip-ansi "^6.0.0"
+
 wrap-ansi@^8.0.1, wrap-ansi@^8.1.0:
   version "8.1.0"
   resolved "https://registry.yarnpkg.com/wrap-ansi/-/wrap-ansi-8.1.0.tgz#56dc22368ee570face1b49819975d9b9a5ead214"