Added parameter 'loopHealthCheck' in function 'watchDependencies'

lib/monitor.ts

@@ -9,6 +9,7 @@ export type Monitor = {
     init (app: express.Application, shouldCollectDefaultMetrics: boolean, buckets?: number[], version?: string, isErrorCallback?:isErrorCallback, metricsEndpoint?: string):void;
     promclient: typeof import("prom-client");
     watchDependencies(healthCheckCallback: HealthCheckCallback):void;
+    watchDependenciesLoopOf(healthCheckCallback: HealthCheckCallback):void;
     collectDependencyTime(name: string, type: string, statusCode: number, method: string, addr: string, errorMessage: string, start: [number, number]):void;
     collectRequestTime(type: string, statusCode: number, addr: string, start: [number, number], errorMessage?: string): void;
     getAddress(request: express.Request):string;
@@ -256,6 +257,19 @@ function watchDependencies(healthCheck: HealthCheckCallback) {
     }
 }
 
+/**
+ * Inits a routine to register the health of the app's dependencies.
+ * Needs to return a valid array of HealthCheckResult.
+ * @param {HealthCheckCallback} healthCheck
+ */
+function watchDependenciesLoopOf(healthCheck: HealthCheckCallback) {
+    if (typeof healthCheck === 'function') {
+        healthCheck(registerDependencyMetrics)
+    } else {
+        console.log("[Express Monitor][Watch Dependencies Loop Of]: healthCheck callback needs to be a valid function")
+    }
+}
+
 /**
  * Registers the current metrics for a specific dependency
  * @param {HealthCheckResult} result  the result of health checking a specific dependency
@@ -269,6 +283,7 @@ function registerDependencyMetrics(result: HealthCheckResult): void {
     init,
     promclient,
     watchDependencies,
+    watchDependenciesLoopOf,
     collectDependencyTime,
     collectRequestTime,
     getAddress

test/app_test.js

@@ -8,6 +8,12 @@ const app = express()
 
 Monitor.init(app, true)
 
+// inits a routine to expose health metrics with no loop
+Monitor.watchDependenciesLoopOf((register) => {
+  register({ name: "Fake dependency 1", up: true});
+  register({ name: "Fake dependency 2", up: false});
+});
+
 app.get('/test', (req, res) => {
 	res.status(200)
 	res.send('test')

test/test_monitor.js

@@ -337,4 +337,23 @@ describe('Collect metrics middleware', () => {
 				expect(res.text).to.include('response_size_bytes{type="http",status="200",method="GET",addr="/users/{userId}",isError="false",errorMessage=""}')
       })
   })
+
+
+  it('should collect healthcheck metrics', () => {
+	chai.request(app)
+		.get('/healthcheck')
+		.set('Content-Type', 'application/json')
+		.send()
+		.end((err) => {
+			if(err) console.log(err)
+		})
+	chai.request(app)
+		.get('/metrics')
+		.set('Content-Type', 'application/json')
+		.send()
+		.end((err, res) => {
+			expect(res.text).to.include('dependency_up{name="Fake dependency 1"} 1')
+			expect(res.text).to.include('dependency_up{name="Fake dependency 2"} 0')
+    })
+  })
 });