first commit

.eslintrc

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+{
+  "env": {
+    "node": true,
+    "es6": true
+  },
+  "extends": ["prettier"]
+}

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Typescript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+

README.md

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+# express-prometheus
+
+Based on [@trussle/tricorder](https://github.com/trussle/tricorder)
+
+## Installation and Setup
+
+WIP
+
+## API
+
+WIP

lib/index.d.ts

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+import * as promClient from "prom-client";
+import * as express from "express";
+
+export const client: typeof promClient; 
+export declare function instrument (server: express.Express): void;

lib/index.js

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+const client = require("prom-client")
+
+client.collectDefaultMetrics();
+
+const metric = {
+  http: {
+    requests: {
+      clients: new client.Gauge({
+        name: "http_requests_processing",
+        help: "Http requests in progress",
+        labelNames: ["method", "path", "status"]
+      }),
+      throughput: new client.Counter({
+        name: "http_requests_total",
+        help: "Http request throughput",
+        labelNames: ["method", "path", "status"]
+      }),
+      duration: new client.Histogram({
+        name: "http_request_duration_seconds",
+        help: "Request duration histogram in seconds",
+        labelNames: ["method", "path", "status"]
+      })
+    }
+  }
+};
+
+function defaultOptions(options) {
+  options = options || {};
+  options.url = options.url || "/metrics";
+  return options;
+}
+
+function isPathExcluded(options, path) {
+  if (!options.excludePaths) {
+    return false
+  } else {
+    return options.excludePaths.some(pathToExclude => {
+      let regExp = new RegExp(pathToExclude)
+      return regExp.test(path)
+    })
+  }
+}
+
+function instrument(server, options) {
+  const opt = defaultOptions(options);
+
+  function middleware(req, res, next) {
+    // If path is the excluded paths list, we don't add a metric for it :)
+    if (isPathExcluded(opt, req.path)) {
+      return next()
+    }
+    if (req.path !== opt.url) {
+      const end = metric.http.requests.duration.startTimer();
+      metric.http.requests.clients.inc(1, Date.now());
+
+      res.on("finish", function () {
+        const labels = {
+          method: req.method,
+          path: req.route ? req.baseUrl + req.route.path : req.path,
+          status: res.statusCode
+        };
+
+        metric.http.requests.clients.dec(1, Date.now());
+        metric.http.requests.throughput.inc(labels, 1, Date.now());
+        end(labels);
+      });
+    }
+
+    return next();
+  }
+
+  server.use(middleware);
+
+  server.get(opt.url, (req, res) => {
+    res.header("content-type", "text/plain; charset=utf-8");
+    return res.send(client.register.metrics());
+  });
+}
+module.exports = {
+  client,
+  instrument
+};

lib/index.test.js

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+const supertest = require("supertest");
+const express = require("express");
+const tricorder = require("./index");
+
+describe("index", () => {
+  let sut;
+
+  describe("options", () => {
+    beforeEach(() => {
+      sut = express();
+    });
+
+    test("When not given url, should default to metrics", () => {
+      // Arrange
+      tricorder.instrument(sut);
+      // Act
+      return supertest(sut)
+        .get("/metrics")
+        .then(result => {
+          // Assert
+          expect(result.statusCode).toBe(200);
+        });
+    });
+
+    test("When given url, should default to url value", () => {
+      // Arrange
+      const options = {
+        url: "/metric-route"
+      };
+      tricorder.instrument(sut, options);
+
+      // Act
+      return supertest(sut)
+        .get(options.url)
+        .then(result => {
+          // Assert
+          expect(result.statusCode).toBe(200);
+        });
+    });
+  });
+
+  describe("metrics", () => {
+    let agent;
+
+    beforeEach(() => {
+      sut = express();
+      tricorder.instrument(sut);
+
+      sut.get("/resource", (req, res) => {
+        res.send();
+      });
+
+      sut.get("/resource/:id", (req, res) => {
+        res.send();
+      });
+
+      agent = supertest.agent(sut);
+    });
+
+    describe("http_requests_processing", () => {
+      test("Given metrics are running, should include http_requests_processing", () => {
+        // Arrange
+        // Act
+        return agent.get("/resource").then(() => {
+          return agent.get("/metrics").then(result => {
+            expect(result.statusCode).toBe(200);
+            expect(result.headers["content-type"]).toBe(
+              "text/plain; charset=utf-8"
+            );
+            expect(result.text).toContain("http_requests_processing 0");
+          });
+        });
+      });
+    });
+
+    describe("http_requests_total", () => {
+      test("Given resource has been request, should being included in http_requests_total", () => {
+        // Arrange
+        // Act
+        return agent.get("/resource").then(() => {
+          return agent.get("/metrics").then(result => {
+            expect(result.statusCode).toBe(200);
+            expect(result.headers["content-type"]).toBe(
+              "text/plain; charset=utf-8"
+            );
+            expect(result.text).toContain(
+              'http_requests_total{method="GET",path="/resource",status="200"} 2'
+            );
+          });
+        });
+      });
+
+      test("Given resource/:id has been request, should being included in http_requests_total", () => {
+        // Arrange
+        const id = 8;
+
+        // Act
+        return agent.get(`/resource/${id}`).then(() => {
+          return agent.get("/metrics").then(result => {
+            expect(result.statusCode).toBe(200);
+            expect(result.headers["content-type"]).toBe(
+              "text/plain; charset=utf-8"
+            );
+            expect(result.text).toContain(
+              'http_requests_total{method="GET",path="/resource/:id",status="200"} 1'
+            );
+          });
+        });
+      });
+    });
+
+    describe("http_request_duration_seconds", () => {
+      test("Given resource has been request, should being included in http_request_duration_seconds", () => {
+        // Arrange
+        // Act
+        return agent.get("/resource").then(() => {
+          return agent.get("/metrics").then(result => {
+            expect(result.statusCode).toBe(200);
+            expect(result.headers["content-type"]).toBe(
+              "text/plain; charset=utf-8"
+            );
+            expect(result.text).toContain(
+              'http_request_duration_seconds_bucket{le="10",method="GET",path="/resource",status="200"} 3'
+            );
+          });
+        });
+      });
+
+      test("Given resource/:id has been request, should being included in http_request_duration_seconds", () => {
+        // Arrange
+        const id = 3;
+
+        // Act
+        return agent.get(`/resource/${id}`).then(() => {
+          return agent.get("/metrics").then(result => {
+            expect(result.statusCode).toBe(200);
+            expect(result.headers["content-type"]).toBe(
+              "text/plain; charset=utf-8"
+            );
+            expect(result.text).toContain(
+              'http_request_duration_seconds_bucket{le="10",method="GET",path="/resource/:id",status="200"} 2'
+            );
+          });
+        });
+      });
+    });
+
+    describe("third party metrics", () => {
+
+      test("Given metrics running, should include default node metrics", () => {
+        // Arrange
+        // Act
+        return agent.get("/metrics").then(result => {
+          // Assert
+          expect(result.text).toContain("nodejs_active_handles_total");
+          expect(result.text).toContain("nodejs_active_requests_total");
+          expect(result.text).toContain("nodejs_external_memory_bytes");
+        });
+      });
+    });
+  });
+
+  describe("labels", () => {
+    let agent;
+
+    beforeEach(() => {
+      sut = express();
+      tricorder.instrument(sut);
+
+      const router = express.Router();
+
+      router.get("/", (req, res) => {
+        res.send();
+      });
+
+      router.get("/:id", (req, res) => {
+        res.send();
+      });
+
+      sut.use("/resource-1", router);
+      sut.use("/resource-2", router);
+
+      sut.get("/resource-3/", (req, res) => {
+        res.send();
+      });
+
+      sut.get("/resource-3/:id", (req, res) => {
+        res.send();
+      });
+
+      agent = supertest.agent(sut);
+    });
+
+    test("Given a router route is called, should calculate path correctly", () => {
+      // Arrange
+      // Act
+      return agent.get("/resource-1/id-thing").then(() => {
+        return agent.get("/metrics").then(result => {
+          expect(result.statusCode).toBe(200);
+          expect(result.headers["content-type"]).toBe(
+            "text/plain; charset=utf-8"
+          );
+          expect(result.text).toContain(
+            'http_requests_total{method="GET",path="/resource-1/:id",status="200"} 1'
+          );
+        });
+      });
+    });
+
+    test("Given a app route is called, should calculate path correctly", () => {
+      // Arrange
+      // Act
+      return agent.get("/resource-3/id-thing-3").then(() => {
+        return agent.get("/metrics").then(result => {
+          expect(result.statusCode).toBe(200);
+          expect(result.headers["content-type"]).toBe(
+            "text/plain; charset=utf-8"
+          );
+          expect(result.text).toContain(
+            'http_requests_total{method="GET",path="/resource-3/:id",status="200"} 1'
+          );
+        });
+      });
+    });
+  });
+});