feat: add prometheus metrics evaluation example (#677)

Co-authored-by: Giovanni Liva <giovanni.liva@dynatrace.com>
Closes #65

functions-runtime/README.md

@@ -22,4 +22,9 @@ docker run -e SCRIPT=https://raw.githubusercontent.com/keptn/lifecycle-toolkit/m
 docker run -e SCRIPT=https://raw.githubusercontent.com/keptn/lifecycle-toolkit/main/functions-runtime/samples/ts/slack.ts -e SECURE_DATA='{ "slack_hook":"hook/parts","text":"this is my test message" }' -it keptnsandbox/klc-runtime:${VERSION}
 ```
 
+### Docker with function and external data - prometheus
+```
+docker run -e SCRIPT=https://raw.githubusercontent.com/keptn/lifecycle-toolkit/main/functions-runtime/samples/ts/prometheus.ts -e DATA='{ "url":"http://localhost:9090", "metrics": "up{service=\"kubernetes\"}", "expected_value": "1" }' -it ghcr.keptn.sh/keptn/functions-runtime:${VERSION}
+```
+
 <img referrerpolicy="no-referrer-when-downgrade" src="https://static.scarf.sh/a.png?x-pxid=858843d8-8da2-4ce5-a325-e5321c770a78" />

functions-runtime/samples/ts/prometheus.ts

@@ -0,0 +1,63 @@
+const text = Deno.env.get("DATA")!;
+let data;
+if (text && text != "") {
+  try {
+    data = JSON.parse(text);
+    if (!data.metrics || !data.url || !data.expected_value) {
+      console.log("Missing mandatory arguments.");
+      printUsage();
+    }
+  } catch {
+    console.error("Error Parsing Json => ", text);
+    Deno.exit(1);
+  }
+} else {
+  console.log("Missing mandatory enviornment variable DATA.");
+  printUsage();
+}
+
+function printUsage() {
+  console.log(
+    'Expecting environment variable DATA in this format => DATA=\'{ "url":"<PROMETHEUS_URL>", "metrics": "<PROMETHEUS_QUERY>", "expected_value": "<EXPECTED_VALUE>" }\' ',
+  );
+  console.log(
+    'Example: export DATA=\'{ "url":"http://localhost:9090", "metrics": "up{service=\\"kubernetes\\"}", "expected_value": "1" }\' ',
+  );
+  Deno.exit(1);
+}
+
+function getPrometheusURL(url: string, metrics: string): string {
+  const dateTime = new Date().toISOString();
+  const hasPort = url.includes(":9090");
+  const hasProtocol = url.includes("http://");
+  let queryURL: string = url;
+  if (!hasPort) {
+    queryURL = queryURL + ":9090";
+  }
+  if (!hasProtocol) {
+    queryURL = "http://" + queryURL;
+  }
+
+  return queryURL + "/api/v1/query?query=" + metrics + "&time=" + dateTime;
+}
+
+const promtheusURL = getPrometheusURL(data.url, data.metrics);
+console.log("Prometheus URL => " + promtheusURL);
+let value;
+try {
+  const jsonResponse = await fetch(promtheusURL);
+  const jsonData = await jsonResponse.json();
+  value = jsonData.data.result[0].value[1];
+} catch (error) {
+  console.error("Could not fetch data from Prometheus.\n", error);
+  Deno.exit(1);
+}
+
+console.log("Expected Value => " + data.expected_value + ", Value => " + value);
+if (value == data.expected_value) {
+  console.log("Evaluation Successful");
+  Deno.exit(0);
+} else {
+  console.log("Evaluation Failed");
+  Deno.exit(1);
+}