bitbake: hashserv: Use separate threads for answering requests and handling them

Experience with the prserv shows that having two threads, one accepting
and queueing connections and one handling the requests leads to much
more reliable behaviour than having everything in a single thread.

(Bitbake rev: a03d60671a53d9ff70e07cc42fe35f6f8776dac2)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/hashserv/__init__.py

@@ -10,6 +10,9 @@ import sqlite3
 import json
 import traceback
 import logging
+import socketserver
+import queue
+import threading
 from datetime import datetime
 
 logger = logging.getLogger('hashserv')
@@ -135,6 +138,41 @@ class HashEquivalenceServer(BaseHTTPRequestHandler):
             self.send_error(400, explain=traceback.format_exc())
             return
 
+class ThreadedHTTPServer(HTTPServer):
+    quit = False
+
+    def serve_forever(self):
+        self.requestqueue = queue.Queue()
+        self.handlerthread = threading.Thread(target=self.process_request_thread)
+        self.handlerthread.daemon = False
+
+        self.handlerthread.start()
+        super().serve_forever()
+
+    def process_request_thread(self):
+        while not self.quit:
+            try:
+                (request, client_address) = self.requestqueue.get(True)
+            except queue.Empty:
+                continue
+            if request is None:
+                continue
+            try:
+                self.finish_request(request, client_address)
+            except Exception:
+                self.handle_error(request, client_address)
+            finally:
+                self.shutdown_request(request)
+
+    def process_request(self, request, client_address):
+        self.requestqueue.put((request, client_address))
+
+    def server_close(self):
+        super().server_close()
+        self.quit = True
+        self.requestqueue.put((None, None))
+        self.handlerthread.join()
+
 def create_server(addr, dbname, prefix=''):
     class Handler(HashEquivalenceServer):
         pass
@@ -171,4 +209,5 @@ def create_server(addr, dbname, prefix=''):
         cursor.execute('CREATE INDEX IF NOT EXISTS outhash_lookup ON tasks_v2 (method, outhash)')
 
     logger.info('Starting server on %s', addr)
-    return HTTPServer(addr, Handler)
+
+    return ThreadedHTTPServer(addr, Handler)