⚡ Fix Head-of-Line Blocking in InMemory Job Backend

crates/rustapi-jobs/src/backend/memory.rs

@@ -34,19 +34,26 @@ impl JobBackend for InMemoryBackend {
             .lock()
             .map_err(|_| JobError::BackendError("Lock poisoned".to_string()))?;
 
-        // Simple FIFO for now, ignoring run_at logic complexity for basic in-memory
-        // In reality we should scan for ready jobs
-        if let Some(job) = q.front() {
+        let now = chrono::Utc::now();
+        let mut index_to_remove = None;
+
+        // Scan the queue for the first ready job
+        for (i, job) in q.iter().enumerate() {
             if let Some(run_at) = job.run_at {
-                if run_at > chrono::Utc::now() {
-                    return Ok(None);
+                if run_at > now {
+                    continue;
                 }
             }
-        } else {
-            return Ok(None);
+            // Found a ready job (no run_at, or run_at <= now)
+            index_to_remove = Some(i);
+            break;
         }
 
-        Ok(q.pop_front())
+        if let Some(i) = index_to_remove {
+            Ok(q.remove(i))
+        } else {
+            Ok(None)
+        }
     }
 
     async fn complete(&self, _job_id: &str) -> Result<()> {

crates/rustapi-jobs/tests/repro_blocking.rs

@@ -0,0 +1,71 @@
+use async_trait::async_trait;
+use rustapi_jobs::{EnqueueOptions, InMemoryBackend, Job, JobContext, JobQueue, Result};
+use serde::{Deserialize, Serialize};
+use std::sync::{Arc, Mutex};
+use std::time::Duration;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+struct SimpleJobData {
+    id: i32,
+}
+
+#[derive(Clone)]
+struct SimpleJob {
+    processed_ids: Arc<Mutex<Vec<i32>>>,
+}
+
+#[async_trait]
+impl Job for SimpleJob {
+    const NAME: &'static str = "simple_job";
+    type Data = SimpleJobData;
+
+    async fn execute(&self, _ctx: JobContext, data: Self::Data) -> Result<()> {
+        self.processed_ids.lock().unwrap().push(data.id);
+        Ok(())
+    }
+}
+
+#[tokio::test]
+async fn test_head_of_line_blocking() {
+    let backend = InMemoryBackend::new();
+    let queue = JobQueue::new(backend);
+
+    let processed_ids = Arc::new(Mutex::new(Vec::new()));
+    let job = SimpleJob {
+        processed_ids: processed_ids.clone(),
+    };
+
+    queue.register_job(job).await;
+
+    // 1. Enqueue a job scheduled far in the future (Job 1)
+    let opts_future = EnqueueOptions::new().delay(Duration::from_secs(3600));
+    queue
+        .enqueue_opts::<SimpleJob>(SimpleJobData { id: 1 }, opts_future)
+        .await
+        .unwrap();
+
+    // 2. Enqueue a job scheduled now (Job 2)
+    queue
+        .enqueue::<SimpleJob>(SimpleJobData { id: 2 })
+        .await
+        .unwrap();
+
+    // 3. Attempt to process one job.
+    // Job 2 should be picked up because Job 1 is not ready.
+    let result = queue.process_one().await.unwrap();
+
+    // Verify
+    if result {
+        // If it processed something, it MUST be Job 2
+        let ids = processed_ids.lock().unwrap().clone();
+        assert_eq!(ids.len(), 1);
+        assert_eq!(
+            ids[0], 2,
+            "Should have processed Job 2, but processed {:?}",
+            ids
+        );
+    } else {
+        // If it returned false, it means it was blocked by Job 1
+        panic!("Head-of-line blocking detected! Failed to process Job 2 because Job 1 is blocking the queue.");
+    }
+}