fix(prefork): propagate cancel_running_job to running children (#82)

crates/taskito-core/src/worker.rs

@@ -13,4 +13,13 @@ pub trait WorkerDispatcher: Send + Sync {
 
     /// Signal the pool to stop accepting new work.
     fn shutdown(&self);
+
+    /// Notify the pool that a running job should be cancelled.
+    ///
+    /// Pools that run tasks in-process (e.g. the thread pool) can rely on the
+    /// storage cancel flag and provide a no-op. Pools that execute tasks in a
+    /// separate process (e.g. the prefork pool) must use this hook to deliver
+    /// a side-channel signal so the worker observes the cancel without polling
+    /// storage.
+    fn notify_cancel(&self, _job_id: &str) {}
 }

crates/taskito-python/src/prefork/child.rs

@@ -29,6 +29,15 @@ impl ChildWriter {
     pub fn send_shutdown(&mut self) {
         let _ = self.send(&ParentMessage::Shutdown);
     }
+
+    /// Send a cooperative-cancel request for `job_id`. Returns the underlying
+    /// I/O error if the pipe is broken so the caller can decide whether to
+    /// retry or drop the request.
+    pub fn send_cancel(&mut self, job_id: &str) -> std::io::Result<()> {
+        self.send(&ParentMessage::Cancel {
+            job_id: job_id.to_string(),
+        })
+    }
 }
 
 /// Reader half — reads result messages from the child process via stdout.