Dynamically reduce DASH worker pool on connection errors

devine/core/manifests/dash.py

@@ -13,6 +13,7 @@ from copy import copy
 from functools import partial
 from hashlib import md5
 from pathlib import Path
+from queue import Queue
 from threading import Event
 from typing import Any, Callable, Optional, Union
 from urllib.parse import urljoin, urlparse
@@ -454,7 +455,7 @@ class DASH:
             else:
                 drm = None
 
-            def download_segment(filename: str, segment: tuple[str, Optional[str]]) -> int:
+            def download_segment(filename: str, segment: tuple[str, Optional[str]], workers: Queue) -> int:
                 if stop_event.is_set():
                     # the track already started downloading, but another failed or was stopped
                     raise KeyboardInterrupt()
@@ -465,6 +466,7 @@ class DASH:
 
                 attempts = 1
                 while True:
+                    workers.put(None)
                     try:
                         if segment_range:
                             # aria2(c) doesn't support byte ranges, let's use python-requests (likely slower)
@@ -486,12 +488,23 @@ class DASH:
                                 silent=attempts != 5,
                                 segmented=True
                             ))
-                        break
+                    except ConnectionRefusedError:
+                        # server likely blocking more than a few connections
+                        # reduce max workers but let this thread continue
+                        with workers.mutex:
+                            _ = workers._get()  # take back this threads queue item
+                            if workers.maxsize > 1:
+                                workers.maxsize -= 1
+                                print(f"REDUCED TRAIN SIZE TO {workers.maxsize}")
                     except Exception as ee:
+                        _ = workers.get()
                         if stop_event.is_set() or attempts == 5:
                             raise ee
                         time.sleep(2)
                         attempts += 1
+                    else:
+                        _ = workers.get()
+                        break
 
                 data_size = segment_save_path.stat().st_size
 
@@ -523,6 +536,7 @@ class DASH:
 
             progress(total=len(segments))
 
+            pool_workers = Queue(maxsize=16)
             finished_threads = 0
             download_sizes = []
             last_speed_refresh = time.time()
@@ -532,7 +546,8 @@ class DASH:
                     pool.submit(
                         download_segment,
                         filename=str(i).zfill(len(str(len(segments)))),
-                        segment=segment
+                        segment=segment,
+                        workers=pool_workers
                     )
                     for i, segment in enumerate(segments)
                 )):