Remove cached binaries on worker startup

as the user could change the compiler at worker startup time (e.g. clang vs gcc),
the binary cache might contain binaries compiled with a different compiler
than the ones generated by the worker. As different compilers lead to binaries of
different speed, test results could be biased, unless we assure that the same compiler
is used for both base and new test.

This patch just clears the binary cache once at worker startup,
leaving the caching mechanism unchanged otherwise.

Possibly the binary cache should also be flushed on worker update
(e.g. the architecture selection logic might change). This is not implemented.

fixes #1666

worker/games.py

@@ -1088,7 +1088,7 @@ def launch_cutechess(
     return task_alive
 
 
-def run_games(worker_info, password, remote, run, task_id, pgn_file):
+def run_games(worker_info, password, remote, run, task_id, pgn_file, clear_binaries):
     # This is the main cutechess-cli driver.
     # It is ok, and even expected, for this function to
     # raise exceptions, implicitly or explicitly, if a
@@ -1176,7 +1176,7 @@ def parse_options(s):
     # Clean up old engines (keeping the num_bkps most recent).
     worker_dir = Path(__file__).resolve().parent
     testing_dir = worker_dir / "testing"
-    num_bkps = 50
+    num_bkps = 0 if clear_binaries else 50
     try:
         engines = sorted(
             testing_dir.glob("stockfish_*" + EXE_SUFFIX),

worker/sri.txt

@@ -1 +1 @@
-{"__version": 202, "updater.py": "PHFUVXcoxBFiW2hTqFN5q5WdAw2pK8uzFC7hyMUC3cLY5bGZPhL8TBGThtqDmcXd", "worker.py": "P3WT0Yhdj/rQ3ZrZ327nM7JQz87NhZC7wggqnqizeJJPbFy49ayo9n7JHoL/7eqv", "games.py": "sgnOBQQ9sZz6AlBg1SP7B1btuY0/p1StAwUtmoVzQk1+I/PjphRKlh2ak4yIpzFP"}
+{"__version": 202, "updater.py": "PHFUVXcoxBFiW2hTqFN5q5WdAw2pK8uzFC7hyMUC3cLY5bGZPhL8TBGThtqDmcXd", "worker.py": "n3LJaWtFmOYeT0jh7v3F/omUQzk3hILlWlK20T+0V2Monj9ZaFLzk58Wat21I0t/", "games.py": "rHw5y0xCbLthLgu1nnBt5n6Viul6M9yvUrpIprMKRtp6+59dQCoTO3WOXoOPKHS3"}

worker/worker.py

@@ -1284,7 +1284,9 @@ def verify_worker_version(remote, username, password):
     return True
 
 
-def fetch_and_handle_task(worker_info, password, remote, lock_file, current_state):
+def fetch_and_handle_task(
+    worker_info, password, remote, lock_file, current_state, clear_binaries
+):
     # This function should normally not raise exceptions.
     # Unusual conditions are handled by returning False.
     # If an immediate exit is necessary then one can set
@@ -1372,7 +1374,7 @@ def fetch_and_handle_task(worker_info, password, remote, lock_file, current_stat
     api = remote + "/api/failed_task"
     pgn_file = [None]
     try:
-        run_games(worker_info, password, remote, run, task_id, pgn_file)
+        run_games(worker_info, password, remote, run, task_id, pgn_file, clear_binaries)
         success = True
     except FatalException as e:
         message = str(e)
@@ -1585,14 +1587,20 @@ def worker():
     # Start the main loop.
     delay = INITIAL_RETRY_TIME
     fish_exit = False
+    clear_binaries = True
     while current_state["alive"]:
         if (worker_dir / "fish.exit").is_file():
             current_state["alive"] = False
             print("Stopped by 'fish.exit' file")
             fish_exit = True
             break
         success = fetch_and_handle_task(
-            worker_info, options.password, remote, lock_file, current_state
+            worker_info,
+            options.password,
+            remote,
+            lock_file,
+            current_state,
+            clear_binaries,
         )
         if not current_state["alive"]:  # the user may have pressed Ctrl-C...
             break
@@ -1606,6 +1614,7 @@ def worker():
                 safe_sleep(delay)
                 delay = min(MAX_RETRY_TIME, delay * 2)
         else:
+            clear_binaries = False
             delay = INITIAL_RETRY_TIME
 
     print("Waiting for the heartbeat thread to finish...")