[tor-commits] [stem/master] Close control socket faster when under load

[atagar@xxxxxxxxxxxxxx]

commit 7d639f217671fcbe44945f07c5e81b250adea625
Author: Damian Johnson <atagar@xxxxxxxxxxxxxx>
Date:   Thu Sep 21 10:11:42 2017 -0700

    Close control socket faster when under load
    
    When receiving a high volume of traffic (such as DEBUG events on a busy relay)
    our controller can take seconds or even minutes to close. This is because we
    send a QUIT signal, then wait for the response which is stuck behind
    potentially thousands of events.
    
    From what I can tell there's little point in issuing a QUIT so dropping that,
    and setting a time limit for processing backlogged events.
---
 docs/change_log.rst |  1 +
 stem/control.py     | 25 ++++++++++++++++---------
 stem/socket.py      |  2 +-
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/docs/change_log.rst b/docs/change_log.rst
index 8d9c10aa..2e421c4f 100644
--- a/docs/change_log.rst
+++ b/docs/change_log.rst
@@ -62,6 +62,7 @@ The following are only available within Stem's `git repository
   * Added :func:`~stem.manual.database` to get a cursor for the manual cache
   * Failed to parse torrcs without a port on ipv6 exit policy entries
   * Resilient to 'Tor' prefix in 'GETINFO version' result (:spec:`c5ff1b1`)
+  * Closing controller connection faster when under heavy event load
   * More succinct trace level logging
 
  * **Descriptors**
diff --git a/stem/control.py b/stem/control.py
index fd5f9f87..ef9919be 100644
--- a/stem/control.py
+++ b/stem/control.py
@@ -281,6 +281,11 @@ import stem.version
 from stem import UNDEFINED, CircStatus, Signal
 from stem.util import str_type, log
 
+# When closing the controller we attempt to finish processing enqueued events,
+# but if it takes longer than this we terminate.
+
+EVENTS_LISTENING_TIMEOUT = 0.1
+
 # state changes a control socket can have
 
 State = stem.util.enum.Enum('INIT', 'RESET', 'CLOSED')
@@ -957,10 +962,20 @@ class BaseController(object):
     socket.
     """
 
+    socket_closed_at = None
+
     while True:
       try:
         event_message = self._event_queue.get_nowait()
         self._handle_event(event_message)
+
+        # Attempt to finish processing enqueued events when our controller closes
+
+        if not self.is_alive():
+          if not socket_closed_at:
+            socket_closed_at = time.time()
+          elif time.time() - socket_closed_at > EVENTS_LISTENING_TIMEOUT:
+            break
       except queue.Empty:
         if not self.is_alive():
           break
@@ -1057,15 +1072,7 @@ class Controller(BaseController):
     self.add_event_listener(_confchanged_listener, EventType.CONF_CHANGED)
 
   def close(self):
-    # making a best-effort attempt to quit before detaching the socket
-    if self.is_authenticated():
-      try:
-        self.msg('QUIT')
-      except:
-        pass
-
-      self.clear_cache()
-
+    self.clear_cache()
     super(Controller, self).close()
 
   def authenticate(self, *args, **kwargs):
diff --git a/stem/socket.py b/stem/socket.py
index eddbfe58..ef2d77c7 100644
--- a/stem/socket.py
+++ b/stem/socket.py
@@ -573,7 +573,7 @@ def recv_message(control_file):
       divider = stem.util.str_tools._to_unicode(divider)
 
     # Most controller responses are single lines, in which case we don't need
-    # some overhead.
+    # so much overhead.
 
     if first_line:
       if divider == ' ':



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