[server] Introduce metrics around clusterSelection in startWorkspaceInstance

 -   'gitpod_server_instance_starts_success_total'
  - 'gitpod_server_instance_starts_failed_total'

Author: geropl

components/server/src/prometheus-metrics.ts

@@ -123,4 +123,26 @@ const gitpodVersionInfo = new prometheusClient.Gauge({
 
 export function setGitpodVersion(gitpod_version: string){
     gitpodVersionInfo.set({gitpod_version}, 1)
+}
+
+const instanceStartsSuccessTotal = new prometheusClient.Counter({
+    name: 'gitpod_server_instance_starts_success_total',
+    help: 'Total amount of successfully performed instance starts',
+    labelNames: ['retries'],
+    registers: [prometheusClient.register],
+});
+
+export function increaseSuccessfulInstanceStartCounter(retries: number = 0) {
+    instanceStartsSuccessTotal.inc({ retries });
+}
+
+const instanceStartsFailedTotal = new prometheusClient.Counter({
+    name: 'gitpod_server_instance_starts_failed_total',
+    help: 'Total amount of failed performed instance starts',
+    labelNames: ['reason'],
+    registers: [prometheusClient.register],
+});
+
+export function increaseFailedInstanceStartCounter(reason: "clusterSelectionFailed") {
+    instanceStartsFailedTotal.inc({ reason });
 }

components/server/src/workspace/workspace-starter.ts

@@ -36,6 +36,7 @@ import { WithReferrerContext } from "@gitpod/gitpod-protocol/lib/protocol";
 import { IDEOption } from "@gitpod/gitpod-protocol/lib/ide-protocol";
 import { Deferred } from "@gitpod/gitpod-protocol/lib/util/deferred";
 import { ExtendedUser } from "@gitpod/ws-manager/lib/constraints";
+import { increaseFailedInstanceStartCounter, increaseSuccessfulInstanceStartCounter } from "../prometheus-metrics";
 
 export interface StartWorkspaceOptions {
     rethrow?: boolean;
@@ -197,8 +198,10 @@ export class WorkspaceStarter {
             }
 
             if (!resp) {
+                increaseFailedInstanceStartCounter("clusterSelectionFailed");
                 throw new Error("cannot start a workspace because no workspace clusters are available");
             }
+            increaseSuccessfulInstanceStartCounter(retries);
 
             span.log({ "resp": resp });