Re: [Ocamlnet-devel] Seeking advice for a couple of issues

[Gerd S. <in...@ge...>]

Am 27.03.2013 23:41:36 schrieb(en) John Derrick:
> Hi All,
> 
> I've been working with Http_client to develop a no-frills CouchDb
> driver. I'm relatively new to OCaml, but have many years of experience
> with various imperative langs.
> 
> I'm looking for help with a couple of issues. My first issue is Basic
> Authentication. I've noticed that Basic Auth and Basic Auth Session
> do not include the "Authorization:" header when making GET or PUT
> requests UNLESS a challenge is received. Is this the expected
> behavior? Not a serious issue as it's easy to add my own
> Authorization entry to the header. Apparently CouchDb does not send  
> an auth challenge.

It is in deed possible to enable this behavior (it's off by default):

  - Create the authentication handler like this:

    let keys = new Http_client.key_ring()
    let auth = new Http_client.basic_auth_handler
                  ~enable_auth_in_advance:true keys

    The enable_auth_in_advance option makes it working.

  - Add credentials:

    let key = Http_client.key ...
    keys # add_key key

  - Add this to the pipeline:

    pipeline # add_auth_handler auth

Well, this behavior has always been a matter of discussion. Normally,  
you don't want to send credentials before you know that the server is  
really the server (remember that you can run http over ssl, and the ssl  
connection authenticates the server), and this way it is specified in  
RFC 2617. Historically, though, browsers have always implemented some  
form of sending the credentials without prior challenge, namely when  
the web page was visited the second time.

> The second issue is chunked request performance. When peforming a
> query against CouchDb (say _all_docs for example) via a GET request,
> Ocamlnet seems to have issues processing the returned data. CouchDb
> returns many small blocks of data in chunked format. Processing a
> collection of 1000 docs can take several minutes. I'm not sure if
> this relates to the event system performance or socket performance.
> Does any one know of a solution to this issue?

I don't think it has to do with the event processing, as the OS buffers  
data up if the client is not fast enough, so for the next read() the  
client gets many chunks at once. Also, 1000 events (if they are really  
generated) are not really much, and should not take minutes, but only  
milliseconds.

Does the client consume a lot of CPU? Or is it just waiting?

In theory there could be a bad interaction with the TCP buffering,  
especially when CouchDB disables the Nagle algorithm (TCP_NODELAY),  
which it probably does. But you report a really bad behavior, so I've  
actually no clue here.

Gerd


> 
> Thanks to all who contributed to the development of Ocamlnet. It's an
> impressive collection of work.
> 
> Regards,
> John
> 
> 
> 
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-- 
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Gerd Stolpmann, Darmstadt, Germany    ge...@ge...
Creator of GODI and camlcity.org.
Contact details:        http://www.camlcity.org/contact.html
Company homepage:       http://www.gerd-stolpmann.de
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