Stop BackgroundProcessor's thread on drop

Without stopping the thread when BackgroundProcessor is dropped, it will
run free. In the context of language bindings, it is difficult to know
how long references held by the thread should live. Implement Drop to
stop the thread just as is done when explicitly calling stop().

diff --git a/lightning-background-processor/src/lib.rs b/lightning-background-processor/src/lib.rs
index f5c914ed5dfe69d158b2d61289f58e64f3b4c5a5..cc4c9e635025117c6b87be05f6615c4788f7092b 100644 (file)
--- a/lightning-background-processor/src/lib.rs
+++ b/lightning-background-processor/src/lib.rs
@@ -43,7 +43,7 @@ pub struct BackgroundProcessor {
        stop_thread: Arc<AtomicBool>,
        /// May be used to retrieve and handle the error if `BackgroundProcessor`'s thread
        /// exits due to an error while persisting.
-       pub thread_handle: JoinHandle<Result<(), std::io::Error>>,
+       pub thread_handle: Option<JoinHandle<Result<(), std::io::Error>>>,
 }
 
 #[cfg(not(test))]
@@ -158,13 +158,27 @@ impl BackgroundProcessor {
                                }
                        }
                });
-               Self { stop_thread: stop_thread_clone, thread_handle: handle }
+               Self { stop_thread: stop_thread_clone, thread_handle: Some(handle) }
        }
 
        /// Stop `BackgroundProcessor`'s thread.
-       pub fn stop(self) -> Result<(), std::io::Error> {
+       pub fn stop(mut self) -> Result<(), std::io::Error> {
+               assert!(self.thread_handle.is_some());
+               self.stop_and_join_thread()
+       }
+
+       fn stop_and_join_thread(&mut self) -> Result<(), std::io::Error> {
                self.stop_thread.store(true, Ordering::Release);
-               self.thread_handle.join().unwrap()
+               match self.thread_handle.take() {
+                       Some(handle) => handle.join().unwrap(),
+                       None => Ok(()),
+               }
+       }
+}
+
+impl Drop for BackgroundProcessor {
+       fn drop(&mut self) {
+               self.stop_and_join_thread().unwrap();
        }
 }