[Haskell-cafe] thread killed

Gregory Collins greg at gregorycollins.net
Thu Apr 5 11:05:38 CEST 2012

+haskell-cafe, oops

On Thu, Apr 5, 2012 at 11:04 AM, Gregory Collins <greg at gregorycollins.net>wrote:

> On Wed, Apr 4, 2012 at 10:09 PM, tsuraan <tsuraan at gmail.com> wrote:
>> > It's hard to rule Snap timeouts out; try building snap-core with the
>> > "-fdebug" flag and running your app with "DEBUG=1", you'll get a spew of
>> > debugging output from Snap on stderr.
>> Heh, that was quite a spew.  I normally get the exceptions tens of MB
>> into files that are hundreds of MB, and I sometimes don't get them at
>> all, so printing out the entire request body was a bit slow :)  After
>> commenting out some of the more talkative debug statements, I got the
>> exception to happen, and it looks generally like this:
> I think I might know what your problem is. You're accepting file uploads
> using handleMultipart, yes? Snap kills uploads that are going too slow,
> otherwise you would be vulnerable to slowloris (
> http://ha.ckers.org/slowloris/) DoS attacks. What's probably happening
> here is that you're doing slow work inside the "Iteratee IO a" handler you
> pass to that function, which makes Snap think the client is trickling bytes
> to you. If that's the case, either finish the iteratee more quickly and do
> the slow work back in the Snap handler (preferable), or disable the minimum
> upload rate guard (although that's not recommended on a server talking to
> the public internet.)
> G
> --
> Gregory Collins <greg at gregorycollins.net>

Gregory Collins <greg at gregorycollins.net>
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