free memory after a thread completes

-> prior all threads that fetched items from the server and their
results stayed in memory until the sync was finished

jellyfin_kodi/downloader.py

@@ -7,7 +7,7 @@ import threading
 import concurrent.futures
 from datetime import date
 
-from six.moves import range, queue as Queue, zip
+from six.moves import range, queue as Queue
 
 from kodi_six import xbmc
 import requests
@@ -183,7 +183,6 @@ def get_item_count(parent_id, item_type=None, params=None):
 
     return result.get('TotalRecordCount', 1)
 
-
 def get_items(parent_id, item_type=None, basic=False, params=None):
 
     query = {
@@ -279,20 +278,33 @@ def _get_items(query, server_id=None):
         # complete all tasks before allowing any results to be processed. ThreadPoolExecutor
         # allows for completed tasks to be processed while other tasks are completed on other
         # threads. Dont be a dummy.Pool, be a ThreadPoolExecutor
-        p = concurrent.futures.ThreadPoolExecutor(DTHREADS)
+        with concurrent.futures.ThreadPoolExecutor(DTHREADS) as p:
+            # dictionary for storing the jobs and their results
+            jobs = {}
 
-        thread_buffer = threading.Semaphore(2 * LIMIT * DTHREADS)
+            # semaphore to avoid fetching complete library to memory
+            thread_buffer = threading.Semaphore(LIMIT * DTHREADS)
 
+            # wrapper function for _get that uses a semaphore
             def get_wrapper(params):
                 thread_buffer.acquire()
                 return _get(url, params, server_id=server_id)
 
-        results = p.map(get_wrapper, query_params)
+            # create jobs
+            for param in query_params:
+                job = p.submit(get_wrapper, param)
+                # the query params are later needed again
+                jobs[job] = param
 
-        for params, result in zip(query_params, results):
-            query['params'] = params
+            # process complete jobs
+            for job in concurrent.futures.as_completed(jobs):
+                # get the result
+                result = job.result() or {'Items': []}
+                query['params'] = jobs[job]
 
-            result = result or {'Items': []}
+                # free job memory
+                del jobs[job]
+                del job
 
                 # Mitigates #216 till the server validates the date provided is valid
                 if result['Items'][0].get('ProductionYear'):
@@ -308,6 +320,8 @@ def _get_items(query, server_id=None):
                 items['RestorePoint'] = query
                 yield items
                 del items['Items'][:]
+
+                # release the semaphore again
                 thread_buffer.release()