stack trace dump extension: also dump engine status, and support triggering it with SIGQUIT, besides SIGUSR2

docs/topics/extensions.rst

@@ -357,15 +357,25 @@ Stack trace dump extension
 
 .. class:: scrapy.contrib.debug.StackTraceDump
 
-Dumps the stack trace of a runnning Scrapy process when a `SIGUSR2`_ signal is
-received. After the stack trace is dumped, the Scrapy process continues running
-normally.
+Dumps the stack trace and Scrapy engine status of a runnning process when a
+`SIGQUIT`_ or `SIGUSR2`_ signal is received. After the stack trace and engine
+status is dumped, the Scrapy process continues running normally.
 
-The stack trace is sent to standard output.
+The dump is sent to standard output.
 
 This extension only works on POSIX-compliant platforms (ie. not Windows).
 
+There are at least two ways to send Scrapy the `SIGQUIT`_ signal:
+
+1. By pressing Ctrl-\ while a Scrapy process is running (Linux only?)
+
+2. By running this command (assuming ``<pid>`` is the process id of the Scrapy
+   process)::
+
+    kill -QUIT <pid>
+
 .. _SIGUSR2: http://en.wikipedia.org/wiki/SIGUSR1_and_SIGUSR2
+.. _SIGQUIT: http://en.wikipedia.org/wiki/SIGQUIT
 
 Debugger extension
 ~~~~~~~~~~~~~~~~~~

scrapy/contrib/debug.py

@@ -8,18 +8,21 @@ import signal
 import traceback
 from pdb import Pdb
 
+from scrapy.utils.engine import print_engine_status
+
 
 class StackTraceDump(object):
     def __init__(self):
         try:
             signal.signal(signal.SIGUSR2, self.dump_stacktrace)
+            signal.signal(signal.SIGQUIT, self.dump_stacktrace)
         except AttributeError:
             # win32 platforms don't support SIGUSR signals
             pass
 
     def dump_stacktrace(self, signum, frame):
-        print "Got signal. Dumping stack trace..."
         traceback.print_stack(frame)
+        print_engine_status()
 
 
 class Debugger(object):