Add the ability to pause the threadpool.

voussoirkit/threadpool.py

@@ -17,13 +17,19 @@ class PoolClosed(ThreadPoolException):
     pass
 
 class ThreadPool:
-    def __init__(self, size):
+    def __init__(self, size, paused=False):
+        '''
+        paused:
+            The pool will start in a paused state and you will have to call
+            `clear_done_and_start_jobs` to start it.
+        '''
         if not isinstance(size, int):
             raise TypeError(f'size must be an int, not {type(size)}.')
         if size < 1:
             raise ValueError(f'size must be >= 1, not {size}.')
         self.max_size = size
         self.closed = False
+        self.paused = paused
         self.jobs = []
         self.job_manager_lock = threading.Lock()
 
@@ -64,7 +70,7 @@ class ThreadPool:
         '''
         When a job finishes, it will call here.
         '''
-        if self.closed:
+        if self.closed or self.paused:
             return
         self.clear_done_and_start_jobs()
 
@@ -91,6 +97,7 @@ class ThreadPool:
         '''
         self.assert_not_closed()
         self.job_manager_lock.acquire()
+
         job = Job(
             pool=self,
             function=function,
@@ -99,7 +106,10 @@ class ThreadPool:
             kwargs=kwargs,
         )
         self.jobs.append(job)
-        self._clear_done_and_start_jobs()
+
+        if not self.paused:
+            self._clear_done_and_start_jobs()
+
         self.job_manager_lock.release()
         return job
 
@@ -107,14 +117,17 @@ class ThreadPool:
         '''
         Remove finished and raised jobs from the queue and start some new jobs.
 
-        This function will be called automatically while adding new jobs and
-        when a job finishes, so you should not have to call it yourself.
+        The job queue is maintained automatically while adding new jobs and
+        when a job finishes, as long as the pool is not paused, so you should
+        not have to call it yourself. If you do pause the pool, use this method
+        to restart it.
 
         Because the pool's internal job queue is flushed regularly, you should
         store your own references to jobs to get their return values.
         '''
         self.job_manager_lock.acquire()
         self._clear_done_and_start_jobs()
+        self.paused = False
         self.job_manager_lock.release()
 
     def join(self):