Switched metadata IO to greenlet

openflexure_microscope/captures/capture.py

@@ -131,8 +131,9 @@ class CaptureObject(object):
         # Stream for buffering capture data
         self.stream = io.BytesIO()
         # Event to notify when the stream has finished writing to disk
-        #self.file_ready = Event()
         self.file_ready = gevent.event.Event()
+        # Access lock for the disk file
+        self.lock = gevent.lock.BoundedSemaphore()
 
         # Store a nice ID
         self.id = uuid.uuid4()  #: str: Unique capture ID
@@ -161,6 +162,7 @@ class CaptureObject(object):
         self.stream.write(s)
 
     def _stream_to_file(self):
+        with self.lock:
             logging.info(f"Writing to disk {self.file}")
             with FileObjectThread(open(self.file, "wb"), 'wb')  as outfile:
                 outfile.write(self.stream.getbuffer())
@@ -246,7 +248,7 @@ class CaptureObject(object):
         self.save_metadata()
 
     def save_metadata(self) -> None:
-        gevent.get_hub().threadpool.spawn(self.synchronous_save_metadata)
+        gevent.spawn(self.synchronous_save_metadata)
 
     def synchronous_save_metadata(self) -> None:
         """
@@ -255,6 +257,8 @@ class CaptureObject(object):
         global EXIF_FORMATS
 
         if self.format.upper() in EXIF_FORMATS and self.exists:
+            self.file_ready.wait()
+            with self.lock:
                 logging.debug("Writing exif data to capture file")
                 # Extract current Exif data
                 exif_dict = piexif.load(self.file)