domenukk · January 3, 2019 20:19 · Jan 3, 2019
diff --git a/py b/py
@@ -0,0 +1,74 @@
+#!/bin/env python
+"""
+A simple example calling any functon in the foreground from background threads, including a response, using Queues.
+"""
+from multiprocessing import Queue, Process, cpu_count
+from collections import namedtuple
+import traceback
+
+Event = namedtuple("Event", "thread_id function args kwargs")
+
+
+
+def done(thread_id, request_queue, response_queue):
+    request_queue.put(Event(thread_id, "done", [], {}))
+
+
+def call_from_bg(thread_id, request_queue, response_queue, func, *args, **kwargs):
+    request_queue.put(Event(thread_id, func, args, kwargs))
+    return response_queue.get()
+
+
+def background_thread(thread_id, *queues):
+    try:
+        def call(func, *args, **kwargs):
+            return call_from_bg(thread_id, *queues, func, *args, **kwargs)
+
+        for i in range(1000):
+            print("{}: calling on main".format(thread_id))
+            resp = call("on_main", "{}: Hello from the foreground :) ({})".format(thread_id, i))
+            print("{}: Foreground responded: {}".format(thread_id, resp))
+    except Exception as ex:
+        print("An exception occurred: {}".format(ex))
+        traceback.print_exc()
+    finally:
+        done(thread_id, *queues)
+
+
+# Example foo
+counter = 0
+
+
+def on_main(*args):
+    global counter
+    counter += 1
+    print(*args)
+    return "Already counted to: {}".format(counter)
+
+
+def main_thread(n_threads):
+    request_queue = Queue()
+    response_queues = []
+
+    threads = []
+    done = []
+    for i in range(n_threads):
+        response_queue = Queue()
+        response_queues.append(response_queue)
+        threads.append(Process(target=background_thread, args=[i, request_queue, response_queue]))
+        threads[i].start()
+    while not len(done) == n_threads:
+        event = request_queue.get()
+        if event.function == "done":
+            done.append(threads[event.thread_id])
+        else:
+            try:
+                response_queues[event.thread_id].put(globals()[event.function](*event.args, **event.kwargs))
+            except Exception as ex:
+                response_queues[event.thread_id].put(ex)
+    for p in done:
+        p.join()
+
+
+if __name__ == '__main__':
+    main_thread(cpu_count() * 2)