Fix pending requests in preview that could stall out the webui (#684)

crates/arroyo-api/src/jobs.rs

@@ -22,7 +22,7 @@ use std::convert::Infallible;
 use std::{collections::HashMap, time::Duration};
 use tokio_stream::wrappers::ReceiverStream;
 use tokio_stream::StreamExt as _;
-use tonic::Request;
+use tonic::{Code, Request};
 use tracing::info;
 
 const PREVIEW_TTL: Duration = Duration::from_secs(60);
@@ -441,6 +441,7 @@ pub async fn get_job_output(
 
     // validate that the job exists, the user has access, and the graph has a GrpcSink
     query_job_by_pub_id(&pipeline_pub_id, &job_pub_id, &db, &auth_data).await?;
+
     let pipeline = query_pipeline_by_pub_id(&pipeline_pub_id, &db, &auth_data).await?;
 
     if !pipeline
@@ -463,7 +464,10 @@ pub async fn get_job_output(
             job_id: job_pub_id.clone(),
         }))
         .await
-        .unwrap()
+        .map_err(|e| match e.code() {
+            Code::FailedPrecondition | Code::NotFound => bad_request(e.message().to_string()),
+            _ => log_and_map(e),
+        })?
         .into_inner();
 
     info!("Subscribed to output");

crates/arroyo-controller/src/lib.rs

@@ -408,13 +408,28 @@ impl ControllerGrpc for ControllerServer {
         &self,
         request: Request<GrpcOutputSubscription>,
     ) -> Result<Response<Self::SubscribeToOutputStream>, Status> {
+        let job_id = request.into_inner().job_id;
+        if self
+            .job_state
+            .lock()
+            .await
+            .get(&job_id)
+            .ok_or_else(|| Status::not_found(format!("Job {} does not exist", job_id)))?
+            .state
+            .read()
+            .unwrap()
+            .as_str()
+            != "Running"
+        {
+            return Err(Status::failed_precondition(
+                "Job must be running to read output",
+            ));
+        }
+
         let (tx, rx) = tokio::sync::mpsc::channel(32);
 
         let mut data_txs = self.data_txs.lock().await;
-        data_txs
-            .entry(request.into_inner().job_id)
-            .or_default()
-            .push(tx);
+        data_txs.entry(job_id).or_default().push(tx);
 
         Ok(Response::new(ReceiverStream::new(rx)))
     }

crates/arroyo-controller/src/states/mod.rs

@@ -584,6 +584,7 @@ pub async fn run_to_completion(
 pub struct StateMachine {
     tx: Option<Sender<JobMessage>>,
     pub config: Arc<RwLock<JobConfig>>,
+    pub state: Arc<RwLock<String>>,
     metrics: Arc<tokio::sync::RwLock<HashMap<Arc<String>, JobMetrics>>>,
     db: DatabaseSource,
     scheduler: Arc<dyn Scheduler>,
@@ -601,6 +602,7 @@ impl StateMachine {
         let mut this = Self {
             tx: None,
             config: Arc::new(RwLock::new(config)),
+            state: Arc::new(RwLock::new(status.state.clone())),
             metrics,
             db,
             scheduler,
@@ -726,6 +728,7 @@ impl StateMachine {
         status: JobStatus,
         shutdown_guard: &ShutdownGuard,
     ) {
+        *self.state.write().unwrap() = status.state.clone();
         if *self.config.read().unwrap() != config {
             let update = JobMessage::ConfigUpdate(config.clone());
             {

webui/src/routes/pipelines/PipelineOutputs.tsx

@@ -19,7 +19,7 @@ export function PipelineOutputs({
   const outputSource = useRef<EventSource | undefined>(undefined);
   const currentJobId = useRef<string | undefined>(undefined);
   const [cols, setCols] = useState<any | undefined>(undefined);
-  const [rows, setRows] = useState<any[]>([]);
+  const [rows, _setRows] = useState<any[]>([]);
   const [subscribed, setSubscribed] = useState<boolean>(false);
   const rowsRead = useRef(0);
   const rowsInTable = useRef(0);
@@ -109,7 +109,7 @@ export function PipelineOutputs({
   }, []);
 
   useEffect(() => {
-    if (onDemand && !subscribed) {
+    if ((onDemand && !subscribed) || job.state != 'Running') {
       close();
       return;
     }