GH-4 properly reference cache.prune

also added logging

cellxgene_gateway/prune_process_cache.py

@@ -17,6 +17,7 @@ from cellxgene_gateway.env import ttl
 class PruneProcessCache:
     def __init__(self, cache):
         self.cache = cache
+        self.expire_seconds = (3600 if ttl is None else int(ttl))
 
     def __call__(self):
         while True:
@@ -25,16 +26,14 @@ class PruneProcessCache:
 
     def prune(self):
         timestamp = current_time_stamp()
-
-        processes_to_delete = []
-        for p in self.cache.entry_list:
-            if timestamp - p.timestamp > (3600 if ttl is None else ttl):
-                processes_to_delete.append(p)
-                processes_to_delete
-
+        cutoff = timestamp - self.expire_seconds
+        processes_to_delete = [p for p in self.cache.entry_list if  p.timestamp < cutoff]
+        processes_to_keep = [p for p in self.cache.entry_list if not p.timestamp < cutoff]
+        logging.getLogger("werkzeug").debug(f"Cutoff {cutoff} = timestamp {timestamp} - expire seconds {self.expire_seconds} , keeping {processes_to_keep}")
+        
         for process in processes_to_delete:
             try:
-                cache.prune(process)
+                logging.getLogger("werkzeug").info(f"pruning process {process.pid} ({process.dataset})")
+                self.cache.prune(process)
             except Exception:
-                logging.getLogger("werkzeug").exception("failed to prune process")
-
+                logging.getLogger("werkzeug").exception("failed to prune process {process.pid} ({process.dataset})")