[Haskell-cafe] [web-devel] http-enumerator: redirects, streaming and keep-alive

[Michael Snoyman]

On Wed, Feb 2, 2011 at 10:15 PM, Felipe Almeida Lessa
<felipe.lessa at gmail.com> wrote:
> On Wed, Feb 2, 2011 at 11:57 AM, Michael Snoyman <michael at snoyman.com> wrote:
>> As far as keep-alive goes, I still need to do a bit more research, but
>> my basic idea (with credit to Bryan O'Sullivan):
>>
>> * http (and family) will all take an extra argument, Maybe Manager.
>> * Manager will be an abstract type that will keep an MVar (Map (Host,
>> Port, IsSecure) Socket).
>> * If http is provided with a Manager, then it uses the Socket
>> available in the Manager. If none is available, it creates a new
>> Socket and places it in the Manager.
>> * If http is *not* provided with a Manager, then it creates a new
>> socket and closes it before returning.
>> * There will be a newManager :: IO Manager, and a closeManager ::
>> Manager -> IO (), which closes all Sockets in the Manager and empties
>> out the inner Map.
>
> How about concurrent use of Manager?  Should we do
>
> A)
>  do m <- newManager
>       forM xs $ forkIO $ doSomething m
>
> B)
>  forM xs $ forkIO $ do
>    m <- newManager
>    doSomething m
>
> While B) should work with any sane Manager implementation, it is not
> optimal.  If all your connections are to the same host, than both
> approaches are the same.  But if access hosts O and P, for example,
> than it is possible that Manager m1 has an open connection to O, but
> you try connect to O using another Manager m2.  That means that
> ideally we should support approach A) as well.  However, to support A
> a simple Map inside an MVar isn't sufficient.

Good point: it should be a MVar (Map HostInfo (MVar Socket)) I think*

Thanks,
Michael

* It's late here, just make sure I'm not saying something stupid ;).