From 57759d8e6d3f003ffbebce3467617947aa33c851 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jannes=20H=C3=B6ke?= <jhoeke@uni-bremen.de>
Date: Mon, 30 May 2016 03:16:33 +0200
Subject: [PATCH] [drunk] use actual thread pool and queue new functions into
 the pool instead of starting new threads every time

---
 telegram/ext/dispatcher.py | 55 +++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 24 deletions(-)

diff --git a/telegram/ext/dispatcher.py b/telegram/ext/dispatcher.py
index c715e6007..f6d068bdb 100644
--- a/telegram/ext/dispatcher.py
+++ b/telegram/ext/dispatcher.py
@@ -20,10 +20,9 @@
 
 import logging
 from functools import wraps
-from threading import Thread, BoundedSemaphore, Lock, Event, current_thread
+from threading import Thread, BoundedSemaphore, Lock, Event  # , current_thread
 from time import sleep
-
-from queue import Empty
+from queue import Queue, Empty
 
 from telegram import (TelegramError, NullHandler)
 from telegram.ext.handler import Handler
@@ -32,12 +31,28 @@ from telegram.utils.deprecate import deprecate
 logging.getLogger(__name__).addHandler(NullHandler())
 
 semaphore = None
-async_threads = set()
-""":type: set[Thread]"""
+async_threads = list()
+""":type: list[tuple(Thread, Event, Queue)]"""
 async_lock = Lock()
 DEFAULT_GROUP = 0
 
 
+def pooled(event, queue):
+    """
+    A wrapper to run a thread in a thread pool
+    """
+    while True:
+        logging.info('Waiting for function')
+        func, args, kwargs = queue.get()
+        logging.info('Got function')
+        try:
+            func(*args, **kwargs)
+            logging.info('Executed function')
+        finally:
+            event.clear()
+            semaphore.release()
+
+
 def run_async(func):
     """
     Function decorator that will run the function in a new thread.
@@ -52,31 +67,17 @@ def run_async(func):
     # TODO: handle exception in async threads
     #       set a threading.Event to notify caller thread
 
-    @wraps(func)
-    def pooled(*pargs, **kwargs):
-        """
-        A wrapper to run a thread in a thread pool
-        """
-        try:
-            result = func(*pargs, **kwargs)
-        finally:
-            semaphore.release()
-
-            with async_lock:
-                async_threads.remove(current_thread())
-        return result
-
     @wraps(func)
     def async_func(*pargs, **kwargs):
         """
         A wrapper to run a function in a thread
         """
-        thread = Thread(target=pooled, args=pargs, kwargs=kwargs)
         semaphore.acquire()
-        with async_lock:
-            async_threads.add(thread)
-        thread.start()
-        return thread
+        for thread, event, queue in async_threads:
+            if not event.is_set():
+                event.set()
+                queue.put((func, pargs, kwargs))
+                break
 
     return async_func
 
@@ -110,6 +111,12 @@ class Dispatcher(object):
         global semaphore
         if not semaphore:
             semaphore = BoundedSemaphore(value=workers)
+            for i in range(workers):
+                event = Event()
+                queue = Queue()
+                thread = Thread(target=pooled, args=(event, queue))
+                async_threads.append((thread, event, queue))
+                thread.start()
         else:
             self.logger.debug('Semaphore already initialized, skipping.')