[racket] net/http-client

From: Jay McCarthy (jay.mccarthy at gmail.com)
Date: Tue Sep 24 08:33:46 EDT 2013

I believe the net/cookie was intended to be used for both client and
server. For instance, print-cookie turns a cookie structure into a
string, which is a header that can be used on either side. I think the
only thing that would be needed as far as structure accessors would be
a way to find the cookies for a given path from a collection of
cookies. There's no plans to add this, but it should be very easy to
anyone that has a use to expose the right stuff from net/cookie.

I do think net/cookie is ripe to be improved though. I think something
more like web-server/http/cookie would be better than the interface it


On Mon, Sep 23, 2013 at 8:21 PM, Evan Donahue <emdonahu at gmail.com> wrote:
> As long as people are discussing http client libraries, I've been wondering
> what the status of net/cookie is. It seems that it's geared towards
> server-side cookie management (and I don't see an obvious way to generate
> Cookie: headers from net/cookie structs since none of the accessors are
> exported). Is there an existing or planned cannonical solution to managing
> cookies on the client side?
> Thanks,
> Evan
> On Thu, Sep 19, 2013 at 11:21 AM, Erik Pearson <erik at adaptations.com> wrote:
>> Just finishing up a two day wrestling match with net/url, couchdb, and
>> assorted other incomplete libraries ... I have some fresh insight.
>> First, the new http client library will be very welcome!
>> A quick review of the existing code relieves me of most of my worries
>> about net/url, which is a bit of a beautiful mess. In particular, I think
>> that some of the code that analyzes the header is too brittle. In net/url a
>> header is expected to be nearly perfectly formed. For instance, the
>> "chunked" condition is tested for by a match against the literal header
>> string "Transfer-Encoding: chunked". Just a difference in case, or an extra
>> space somewhere will lead to a false negative. In the new code, this is done
>> by a much more forgiving regexp comparison. However, I'm not sure this goes
>> far enough. More on that in a sec.
>> I would like to make some recommendations:
>> - keep text as bytstrings -- it looks like this is the way the new library
>> works (but not net/url.)
>> - the status line should be parsed and the status code converted to an
>> integer.
>> - The header should be parsed into the simplest usable form. I would
>> suggest that an alist, with the key being a lower cased symbol and the value
>> being the original bytestring.
>> - When forming a header for a request, the same format should be used. I
>> realize that if one wants proper-cased field names, the library will need to
>> perform this formatting.
>> - All information should be made available back to the api user.
>> - Standard header field values should be optionally parsed
>> These changes would make the library much more useful. It would be
>> consistent with http library design across languages. It would also promote
>> more uniformity across Racket libraries which use them. I've found that when
>> diving into a library (currently I'm dealing with couchdb) that has to
>> reinvent the http wheel -- it may be reinvented with a slight twist. If one
>> is using multiple libraries together, each with a different idea of what a
>> header or https status line is, well, things get really unnecessarily
>> complicated.
>> I think the core library could benefit from this as well. For instance,
>> when looking for fields in the header, it would be more reliable to find the
>> field in an alist, than to use an regex to extract values out of the
>> bytestring. This is a very common operation when dealing with http, and I
>> think it should be as simple and reliable as practical.
>> Finally I would recommend that there be a facility for decoding and
>> encoding standard header fields. The application of the parsing would be
>> optional, but I think it is important to have an implementation in the core
>> library. The header field names and formats are well specified, and there
>> are not all that many of them. They could be supplied as a hash or aref,
>> with the field name lower-cased symbol (as in the parsed header) as key and
>> two functions, one to decode from a bytstring, and one to encode into a
>> bytestring. The simplest, most racketiest data structure would be best. A
>> library user could grab this translation database and extend or modify it at
>> will, but they would have a great head start.
>> Anyway, this is far from exhaustive, but these are some of the issues I've
>> grappled with in recent hours and are right on the top of my head.
>> On Tue, Sep 17, 2013 at 6:51 AM, Jay McCarthy <jay.mccarthy at gmail.com>
>> wrote:
>>> I think it's an obvious request, but a character flaw of mine is not
>>> doing things unless they can be done really good. In this case, I see
>>> a hash table as a "parse" of the headers. It's not obvious to me how
>>> to parse them. For example...
>>> - The same header can appear many times, so (Key -> Value) is
>>> incorrect, unless you overwrite one. It would be better to have (Key
>>> -> (Listof Value)) but that feels really ugly since most of the time
>>> there will just be one
>>> - The spec doesn't mandate case sensitivity on headers, so I would
>>> need to canonicalize "ACCept-ENCodiNG" to something else. Maybe
>>> 'Accept-Encoding?
>>> - The value of many headers is not really a string. For instance,
>>> Content-Length is a number, Cache-Control is an association list,
>>> Content-Disposition is complicated, etc. I feel like it is
>>> disingenuous to only partial parse.
>>> - Dealing with all this may be wasted effort for most requests that
>>> just care about the body
>>> For these reasons, I think http-client should just return the list of
>>> bytes. I think it would be nice to have another function that parses
>>> that so clients could optionally call it if it is important. That can
>>> be part of http-client.
>>> Jay
>>> On Tue, Sep 17, 2013 at 3:41 AM, adam moore <nerdfunk at gmail.com> wrote:
>>> > Hi Jay,
>>> >
>>> > Just looking over the new http client code - looking very nice, and
>>> > much better than my current slapped together parsing of
>>> > get-impure-port.
>>> >
>>> > I was wondering if it might be better to pass back the headers as
>>> > something easier to look up against, for example as a hash table? Or
>>> > perhaps, provide an option to do so. I think it's a pretty common use
>>> > case to provide for.
>>> >
>>> > Thanks again,
>>> > Adam
>>> --
>>> Jay McCarthy <jay at cs.byu.edu>
>>> Assistant Professor / Brigham Young University
>>> http://faculty.cs.byu.edu/~jay
>>> "The glory of God is Intelligence" - D&C 93
>>> ____________________
>>>   Racket Users list:
>>>   http://lists.racket-lang.org/users
>> --
>> Erik Pearson
>> Adaptations
>> ;; web form and function
>> ____________________
>>   Racket Users list:
>>   http://lists.racket-lang.org/users

Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University

"The glory of God is Intelligence" - D&C 93

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