[PATCH] mirrorlist_client timeouts

[Matt Domsch]

>From 1aa19dfed950c209ad5a2ddf48e2b828b50c07ee Mon Sep 17 00:00:00 2001
From: Matt Domsch <Matt_Domsch at dell.com>
Date: Wed, 12 May 2010 13:52:51 -0500
Subject: [PATCH] mirrorlist_client: a better way to handle socket timeouts

blocking sockets, calling recv(), may block forever if the server end
doesn't send anything for some reason.  Don't let that happen.  Python
has a socket.settimeout() capability.  We'll use that to let any
individual operation (except the select()) take up to 5 seconds (they
should all be in the microsecond range, so this is very generous), and
let select() continue to wait for 60 seconds for the server to respond
at all.

If a timeout happens, an exception is raised, which is caught by the
caller and a HTTP 503 returned to the web client.
---
 mirrorlist-server/mirrorlist_client.wsgi |   17 ++++++++---------
 1 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/mirrorlist-server/mirrorlist_client.wsgi b/mirrorlist-server/mirrorlist_client.wsgi
index 15b3a15..3508f19 100755
--- a/mirrorlist-server/mirrorlist_client.wsgi
+++ b/mirrorlist-server/mirrorlist_client.wsgi
@@ -13,14 +13,14 @@ import cStringIO
 from datetime import datetime, timedelta
 
 socketfile = '/var/run/mirrormanager/mirrorlist_server.sock'
-request_timeout = 60 # seconds
+select_timeout = 60 # seconds
+timeout = 5 # seconds
 
 def get_mirrorlist(d):
-    try:
-        s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
-        s.connect(socketfile)
-    except:
-        raise
+    # any exceptions or timeouts raised here get handled by the caller
+    s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    s.settimeout(timeout)
+    s.connect(socketfile)
 
     p = pickle.dumps(d)
     del d
@@ -33,8 +33,7 @@ def get_mirrorlist(d):
     del p
 
     # wait for other end to start writing
-    expiry = datetime.utcnow() + timedelta(seconds=request_timeout)
-    rlist, wlist, xlist = select.select([s],[],[],request_timeout)
+    rlist, wlist, xlist = select.select([s],[],[],select_timeout)
     if len(rlist) == 0:
         s.shutdown(socket.SHUT_RD)
         raise socket.timeout
@@ -48,7 +47,7 @@ def get_mirrorlist(d):
 
     readlen = 0
     p = ''
-    while readlen < resultsize and datetime.utcnow() < expiry:
+    while readlen < resultsize:
         p += s.recv(resultsize - readlen)
         readlen = len(p)
     results = pickle.loads(p)
-- 
1.7.0.1


-- 
Matt Domsch
Technology Strategist
Dell | Office of the CTO