[Caml-list] Ocamlnet, netclient and lwt_preemptive causing ocsigen segfault

[Caml-list] Ocamlnet, netclient and lwt_preemptive causing ocsigen segfault

[pierrchp]

 Hello,

I have a web application written using lwt and ocsigen that needs to get data
using https.

In order to do that, I use the Http_client.Convenience module from Ocamlnet, and
use Lwt.detach to perform the call (there probably is a smater way to do this, I
am open to any suggestion). The http call is performed and the data is
displayed, but then the server crashed, apparently because of a segfault.

here is the code for a test eliom module that reproduce the problem, compiled
using

ocamlfind ocamlc -c -thread -package
equeue-ssl,netclient,lwt,lwt.preemptive,ocsigen test_server.ml

Cheers


-Pierre


(*************************************)

open Lwt
open XHTML.M
open Eliom_services
open Eliom_parameters
open Eliom_sessions
open Eliom_predefmod.Xhtml;;




(* initialising Http_client.Convenience to use https *)
  Ssl.init();

   Http_client.Convenience.configure_pipeline
      (fun p ->
         let ctx = Ssl.create_context Ssl.TLSv1 Ssl.Client_context in
             let tct = Https_client.https_transport_channel_type ctx in
                  p # configure_transport Http_client.https_cb_id tct
      )
;;



module H =  Http_client.Convenience


let test_service = new_service ~path:[""]
                               ~get_params:unit
  ()
;;


let test_handler = fun sp () () ->
(* thread that request data from a url *)
Lwt_preemptive.detach (function () -> H.http_get "https://ocsigen.org") () >>=
function s ->
(*page that display the data*)
 return (
html (head (title (pcdata "test")) [])
     (body [
          h1 [pcdata "the data are:"];
          p [ pcdata s]
           ]
     )
)
;;
register test_service test_handler;;

Re: [Caml-list] Ocamlnet, netclient and lwt_preemptive causing ocsigen segfault

[Gerd Stolpmann]

Am Samstag, den 10.09.2011, 20:58 +0200 schrieb pierrchp@free.fr:
> Hello,
> 
> I have a web application written using lwt and ocsigen that needs to get data
> using https.
> 
> In order to do that, I use the Http_client.Convenience module from Ocamlnet, and
> use Lwt.detach to perform the call (there probably is a smater way to do this, I
> am open to any suggestion). The http call is performed and the data is
> displayed, but then the server crashed, apparently because of a segfault.

Run the server under gdb, and get a backtrace after the crash. 

> here is the code for a test eliom module that reproduce the problem, compiled
> using
> 
> ocamlfind ocamlc -c -thread -package
> equeue-ssl,netclient,lwt,lwt.preemptive,ocsigen test_server.ml

Unfortunately, it is still impossible to run Ocamlnet protocol
interpreters on top of Lwt's event dispatcher. I really wished we had
here a better way of combining both systems.

Gerd

> 
> Cheers
> 
> 
> -Pierre
> 
> 
> (*************************************)
> 
> open Lwt
> open XHTML.M
> open Eliom_services
> open Eliom_parameters
> open Eliom_sessions
> open Eliom_predefmod.Xhtml;;
> 
> 
> 
> 
> (* initialising Http_client.Convenience to use https *)
>   Ssl.init();
> 
>    Http_client.Convenience.configure_pipeline
>       (fun p ->
>          let ctx = Ssl.create_context Ssl.TLSv1 Ssl.Client_context in
>              let tct = Https_client.https_transport_channel_type ctx in
>                   p # configure_transport Http_client.https_cb_id tct
>       )
> ;;
> 
> 
> 
> module H =  Http_client.Convenience
> 
> 
> let test_service = new_service ~path:[""]
>                                ~get_params:unit
>   ()
> ;;
> 
> 
> let test_handler = fun sp () () ->
> (* thread that request data from a url *)
> Lwt_preemptive.detach (function () -> H.http_get "https://ocsigen.org") () >>=
> function s ->
> (*page that display the data*)
>  return (
> html (head (title (pcdata "test")) [])
>      (body [
>           h1 [pcdata "the data are:"];
>           p [ pcdata s]
>            ]
>      )
> )
> ;;
> register test_service test_handler;;
> 

-- 
------------------------------------------------------------
Gerd Stolpmann, Darmstadt, Germany    gerd@gerd-stolpmann.de
Creator of GODI and camlcity.org.
Contact details:        http://www.camlcity.org/contact.html
Company homepage:       http://www.gerd-stolpmann.de
*** Searching for new projects! Need consulting for system
*** programming in Ocaml? Gerd Stolpmann can help you.
------------------------------------------------------------

[Caml-list] Re: [Ocsigen] Ocamlnet, netclient and lwt_preemptive causing ocsigen segfault

[Vincent Balat]

[-- Attachment #1: Type: text/plain, Size: 2158 bytes --]

Hello,

No idea about the segmentation fault but if you just want to do an HTTP 
request, Ocsigen Server (without Ocamlnet's netclient) may be enough for your 
needs.
See module Ocsigen_http_client.
http://ocsigen.org/ocsigenserver/2.0-rc1/api/Ocsigen_http_client

(I would be interested to understand the problem with netclient, though).

Vincent Balat



>  Hello,
> 
> I have a web application written using lwt and ocsigen that needs to get
> data using https.
> 
> In order to do that, I use the Http_client.Convenience module from
> Ocamlnet, and use Lwt.detach to perform the call (there probably is a
> smater way to do this, I am open to any suggestion). The http call is
> performed and the data is displayed, but then the server crashed,
> apparently because of a segfault.
> 
> here is the code for a test eliom module that reproduce the problem,
> compiled using
> 
> ocamlfind ocamlc -c -thread -package
> equeue-ssl,netclient,lwt,lwt.preemptive,ocsigen test_server.ml
> 
> Cheers
> 
> 
> -Pierre
> 
> 
> (*************************************)
> 
> open Lwt
> open XHTML.M
> open Eliom_services
> open Eliom_parameters
> open Eliom_sessions
> open Eliom_predefmod.Xhtml;;
> 
> 
> 
> 
> (* initialising Http_client.Convenience to use https *)
>   Ssl.init();
> 
>    Http_client.Convenience.configure_pipeline
>       (fun p ->
>          let ctx = Ssl.create_context Ssl.TLSv1 Ssl.Client_context in
>              let tct = Https_client.https_transport_channel_type ctx in
>                   p # configure_transport Http_client.https_cb_id tct
>       )
> ;;
> 
> 
> 
> module H =  Http_client.Convenience
> 
> 
> let test_service = new_service ~path:[""]
>                                ~get_params:unit
>   ()
> ;;
> 
> 
> let test_handler = fun sp () () ->
> (* thread that request data from a url *)
> Lwt_preemptive.detach (function () -> H.http_get "https://ocsigen.org") ()
> >>= function s ->
> (*page that display the data*)
>  return (
> html (head (title (pcdata "test")) [])
>      (body [
>           h1 [pcdata "the data are:"];
>           p [ pcdata s]
>            ]
>      )
> )
> ;;
> register test_service test_handler;;

[-- Attachment #2: Type: text/html, Size: 14955 bytes --]