Refactor installing signals.

scrapy/crawler.py

@@ -416,15 +416,17 @@ class CrawlerProcess(CrawlerRunner):
                 return
             d.addBoth(self._stop_reactor)
 
-        if install_signal_handlers:
-            install_shutdown_handlers(self._signal_shutdown)
         resolver_class = load_object(self.settings["DNS_RESOLVER"])
         resolver = create_instance(resolver_class, self.settings, self, reactor=reactor)
         resolver.install_on_reactor()
         tp = reactor.getThreadPool()
         tp.adjustPoolsize(maxthreads=self.settings.getint("REACTOR_THREADPOOL_MAXSIZE"))
         reactor.addSystemEventTrigger("before", "shutdown", self.stop)
-        reactor.run(installSignalHandlers=False)  # blocking call
+        if install_signal_handlers:
+            reactor.addSystemEventTrigger(
+                "after", "startup", install_shutdown_handlers, self._signal_shutdown
+            )
+        reactor.run()  # blocking call
 
     def _graceful_stop_reactor(self) -> Deferred:
         d = self.stop()

scrapy/utils/ossignal.py

@@ -19,13 +19,10 @@ def install_shutdown_handlers(
     function: SignalHandlerT, override_sigint: bool = True
 ) -> None:
     """Install the given function as a signal handler for all common shutdown
-    signals (such as SIGINT, SIGTERM, etc). If override_sigint is ``False`` the
-    SIGINT handler won't be install if there is already a handler in place
-    (e.g.  Pdb)
+    signals (such as SIGINT, SIGTERM, etc). If ``override_sigint`` is ``False`` the
+    SIGINT handler won't be installed if there is already a handler in place
+    (e.g. Pdb)
     """
-    from twisted.internet import reactor
-
-    reactor._handleSignals()
     signal.signal(signal.SIGTERM, function)
     if signal.getsignal(signal.SIGINT) == signal.default_int_handler or override_sigint:
         signal.signal(signal.SIGINT, function)