On Wed, Mar 20, 2013 at 12:47:09PM -0700, Noah Kantrowitz wrote:
>
> On Mar 20, 2013, at 12:44 PM, Martin v. Löwis wrote:
>
> > Am 20.03.13 04:27, schrieb R. David Murray:
> >> Example:
> >>
> >> request =
> >> urllib.request.Request("http://www.python.org/~jeremy/";)
> >>
> >> And then there are things like:
> >>
> >> h = client.HTTPSConnection('svn.python.org', 443,
> >> context=context)
> >>
> >> I don't think there are a huge number of these, but we will need to
> >> deal with them.
> >
> > In the past, we just let them break and then fix the test case,
> > which is not the best solution, but also not overly tragic (IMO).
> >
> > Note that the redesign project includes an objective of URL
> > stability. The test suite is here of least concern, as there are
> > thousands of incoming links to various pages. These need to be
> > preserved as much as feasible (possibly using redirects).
>
> +1 on let them break, but when they get fixed it should be against a
> dedicated testing endpoint if possible, preferably something internal
> to the test suite. Maybe spawn an HTTP server in a background
> thread/proc? I would very much like the web infra to not be a runtime
> dependency if possible.
FWIW, that approach isn't possible in all cases. Perfect example
was http://bugs.python.org/issue15285, which required very specific
TCP/IP behavior (specifically with regards to RST) that you simply
can't simulate easily on a localhost.
I set up two services, blackhole and whitehole.snakebite.net, that
have been fulfilling this need for the past ~10 months now.
Relevant blurb below:
def testConnectTimeout(self):
# Testing connect timeout is tricky: we need to have IP connectivity
# to a host that silently drops our packets. We can't simulate this
# from Python because it's a function of the underlying TCP/IP stack.
# So, the following Snakebite host has been defined:
blackhole = ('blackhole.snakebite.net', 56666)
# Blackhole has been configured to silently drop any incoming packets.
# No RSTs (for TCP) or ICMP UNREACH (for UDP/ICMP) will be sent back
# to hosts that attempt to connect to this address: which is exactly
# what we need to confidently test connect timeout.
# However, we want to prevent false positives. It's not unreasonable
# to expect certain hosts may not be able to reach the blackhole, due
# to firewalling or general network configuration. In order to improve
# our confidence in testing the blackhole, a corresponding 'whitehole'
# has also been set up using one port higher:
whitehole = ('whitehole.snakebite.net', 56667)
# This address has been configured to immediately drop any incoming
# packets as well, but it does it respectfully with regards to the
# incoming protocol. RSTs are sent for TCP packets, and ICMP UNREACH
# is sent for UDP/ICMP packets. This means our attempts to connect to
# it should be met immediately with ECONNREFUSED. The test case has
# been structured around this premise: if we get an ECONNREFUSED from
# the whitehole, we proceed with testing connect timeout against the
# blackhole. If we don't, we skip the test (with a message about not
# getting the required RST from the whitehole within the required
# timeframe).
# For the records, the whitehole/blackhole configuration has been set
# up using the 'pf' firewall (available on BSDs), using the following:
#
# ext_if="bge0"
#
# blackhole_ip="35.8.247.6"
# whitehole_ip="35.8.247.6"
# blackhole_port="56666"
# whitehole_port="56667"
#
# block return in log quick on $ext_if proto { tcp udp } \
# from any to $whitehole_ip port $whitehole_port
# block drop in log quick on $ext_if proto { tcp udp } \
# from any to $blackhole_ip port $blackhole_port
#
Regards,
Trent.
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