[dashboard] Start at most one workspace after prebuild finished

Under certain circumstances - if a workspace failure appeared before the ideURL got set - we would never leave the HeadlessLogView but start a new workspace over and over again. As we do not handle this error well, it would only get caught by timeouts (1h), leading to users being effectively blocked because they reached their parallel workspace limit

Author: geropl

components/dashboard/src/start/CreateWorkspace.tsx

@@ -330,19 +330,32 @@ function RunningPrebuildView(props: RunningPrebuildViewProps) {
   const logsEmitter = new EventEmitter();
   const service = getGitpodService();
   let pollTimeout: NodeJS.Timeout | undefined;
+  let prebuildDoneTriggered: boolean = false;
 
   useEffect(() => {
-    const pollIsPrebuildDone = async () => {
-      clearTimeout(pollTimeout!);
-      const available = await service.server.isPrebuildDone(props.runningPrebuild.prebuildID);
-      if (available) {
+    const checkIsPrebuildDone = async (): Promise<boolean> => {
+      if (prebuildDoneTriggered) {
+        console.debug("prebuild done already triggered, doing nothing");
+        return true;
+      }
+
+      const done = await service.server.isPrebuildDone(props.runningPrebuild.prebuildID);
+      if (done) {
+        // note: this treats "done" as "available" which is not equivalent.
+        // This works because the backend ignores prebuilds which are not "available", and happily starts a workspace as if there was no prebuild at all.
+        prebuildDoneTriggered = true;
         props.onPrebuildSucceeded();
-        return;
+        return true;
       }
+      return false;
+    };
+    const pollIsPrebuildDone = async () => {
+      clearTimeout(pollTimeout!);
+      await checkIsPrebuildDone();
       pollTimeout = setTimeout(pollIsPrebuildDone, 10000);
     };
 
-    const disposables = watchHeadlessLogs(service.server, props.runningPrebuild.instanceID, (chunk) => logsEmitter.emit('logs', chunk), pollIsPrebuildDone);
+    const disposables = watchHeadlessLogs(service.server, props.runningPrebuild.instanceID, (chunk) => logsEmitter.emit('logs', chunk), checkIsPrebuildDone);
     return function cleanup() {
       clearTimeout(pollTimeout!);
       disposables.dispose();

components/dashboard/src/start/StartWorkspace.tsx

@@ -346,7 +346,7 @@ function HeadlessWorkspaceView(props: { instanceId: string }) {
 
   useEffect(() => {
     const service = getGitpodService();
-    const disposables = watchHeadlessLogs(service.server, props.instanceId, (chunk) => logsEmitter.emit('logs', chunk), () => {});
+    const disposables = watchHeadlessLogs(service.server, props.instanceId, (chunk) => logsEmitter.emit('logs', chunk), async () => { return false; });
     return function cleanup() {
       disposables.dispose();
     };

components/dashboard/src/start/WorkspaceLogs.tsx

@@ -87,11 +87,13 @@ export default class WorkspaceLogs extends React.Component<WorkspaceLogsProps, W
   }
 }
 
-export function watchHeadlessLogs(server: GitpodServer, instanceId: string, onLog: (chunk: string) => void, checkIsDone: () => Promise<void> | void): DisposableCollection {
+export function watchHeadlessLogs(server: GitpodServer, instanceId: string, onLog: (chunk: string) => void, checkIsDone: () => Promise<boolean>): DisposableCollection {
   const disposables = new DisposableCollection();
 
   const startWatchingLogs = async () => {
-    await checkIsDone();
+    if (await checkIsDone()) {
+      return;
+    }
 
     const retry = async (reason: string, err?: Error) => {
       console.debug("re-trying headless-logs because: " + reason, err);
@@ -155,7 +157,9 @@ export function watchHeadlessLogs(server: GitpodServer, instanceId: string, onLo
       }
       reader.cancel()
 
-      await checkIsDone();
+      if (await checkIsDone()) {
+        return;
+      }
     } catch(err) {
       reader?.cancel().catch(console.debug);
       await retry("error while listening to stream", err);