Re: Seeking advice for a couple of issues

Thanks for the reply, Gerd.

First, I should mention I'm using Ocaml 4.001, the Mingw build on Win7.  I'm 
using Ocamlnet version 3.6.1 (or newer).

I tried using ~enable_auth_in_advance as you suggested but was unable to get 
it working.  I must be doing something wrong.
Here is my latest attempt:

method private do_run_pipe call =
  let keys = new Http_client.key_ring() in
  let auth = new Http_client.basic_auth_handler ~enable_auth_in_advance:true 
keys in
  let key = Http_client.key ~user:"admin" ~password:"admin" ~realm:""
    ~domain:["localhost"] in
  keys#add_key key;
  let pipeline = new Http_client.pipeline in
  pipeline # add_auth_handler auth;
  let hdr = call#request_header `Base in
  hdr#update_field "Content-type" "application/json";
  pipeline#add call;
  pipeline#run();
  call#response_status_code

Packet capture shows that no Authorization header was added to a PUT request 
with the above block of code.  Return code is 401.

On the second issue, I have TCP_NODELAY set to true in the CouchDb config. 
The process is using heavy CPU while it runs.  Do you think the issue could 
be related to OS and/or OCaml build?

Thanks again for your help,
John

-----Original Message----- 
From: Gerd Stolpmann
Sent: Thursday, March 28, 2013 9:06 AM
To: John Derrick
Cc: [email protected]
Subject: AW: [Ocamlnet-devel] Seeking advice for a couple of issues

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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-- 
------------------------------------------------------------
Gerd Stolpmann, Darmstadt, Germany    [email protected]
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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