Re: Update: "Bogus Handlers" error using the WIRE package: where should error handling condition be applied?

On 3/3/07, Madhu <[email protected]> wrote:
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> * "Denis Papathanasiou" <e4044eb40703020617m2d6875dfraa548b47bfbd9678@XXX> :
> |> used an MP function in your code.  I'd guess your bogus handler
> |> messages are from some little tested interaction between MP and the
> |> FD-HANDLERS packages.  Perhaps you can eliminate the MP:PROCESS and
> |> see if you still get the messages?
> |
> | It's plausible to try it in the interim, to find out whether or not
> | that is indeed causing the error, but not using MP in the server
> | creates more problems than it solves.
> |
> | I.e., in a single-threaded mode, when (reload) is busy, none of the
> | public methods in the server process will be responsive enough when
> | they're invoked by any of the client processes.
> |
> | Perhaps we should dump WIRE and switch to a model like what you use
> | ("use TCP/IP on top of the MP package -- i.e. having a CMUCL
> | MP:PROCESS doing a listen, and another to handle each connection.").
> |
> | Do you have any examples/code snippets of that that you could share?
>
> I'm attaching a file that sketches this to this message -- I'm
> reasonably sure it works, but haven't debugged it.
>
> |> appropriate in this case, perhaps you can consider wrapping your code
> |> inside a HANDLER-BIND that uses INVOKE-RESTART.]
> |
> | This may sound like a dumb question -- I really need to go back and
> | study conditions again -- but if CMUCL is offering a restart that
> | solves the problem ("REMOVE-THEM"), then if I were to wrap a
> | handler-bind/invoke-restart (where the restart is "REMOVE-THEM") in
> | the right place in the server code, then I can go on using WIRE and
> | MP, correct?
>
> I need to double check but your handler could search for the restart
> with FIND-RESTART.  If found, you can call INVOKE-RESTART in the
> handler, cross your fingers, and hope the correct condition is being
> handled.  If you don't find the restart, just decline to handle the
> condition. (return NIL in the handler without transferring control)
> --
> Madhu
>

Thanks very much for the replies and code samples; I'll start with
invoke-restart on the current wire mechanism, but if that still
doesn't work, I'll try switching to tcp/ip instead.

>
> --Multipart_Fri_Mar__2_22:58:12_2007-1
> Content-Type: application/octet-stream
> Content-Disposition: attachment; filename="bogus-service.lisp"
> Content-Transfer-Encoding: 7bit
>
> ;;; -*- Mode: LISP; Package: :cl-user; BASE: 10; Syntax: ANSI-Common-Lisp; -*-
> ;;;
> ;;;   Touched: Fri Mar 02 20:17:37 2007 -0700 <[email protected]>
> ;;;   Time-stamp: <07/03/02 20:37:41 madhu>
> ;;;
> ;;;   UNTESTED Sample skeleton code for providing a TCP service with
> ;;;   CMUCL MP. (Loosely based on Douglas Crosher's CL-HTTP port)
> ;;;
> (in-package "CL-USER")
>
> (defvar *bogus-service-invocation-count* 0)
>
> (defun bogus-service (stream &aux n)
>   (sleep 5)
>   (write-string "End of bogus service. You are our " stream)
>   (write (setq n (incf *bogus-service-invocation-count*))
>          :base 10 :stream stream)
>   (write-string (if (<= 11 (setq n (abs (nth-value 1 (truncate n 100)))) 20)
>                     "th"
>                     (case (nth-value 1 (truncate n 10))
>                       (1 "st") (2 "nd") (3 "rd") (t "th")))
>                 stream)
>   (write-string " satisified customer!" stream)
>   (terpri stream)
>   (finish-output stream)
>   (close stream))
>
> (defun make-bogus-tcp-stream (fd)
>   (sys:make-fd-stream fd :output t :input t :element-type 'character))
>
> (defun handle-connection (fd)
>   (multiple-value-bind (client-address port)
>       (ext:get-peer-host-and-port fd)
>     (warn "handle-connection: port=~d client-address=~S" port client-address)
>     (let ((stream (make-bogus-tcp-stream fd)))
>       (mp:make-process (lambda () (bogus-service stream))))))
>
> (defun listen-for-connections (&optional (port 8128) (interface "127.0.0.1"))
>   (flet ((listener ()
>            (let (fd)
>              (unwind-protect
>                   (progn
>                     (setq fd (ext:create-inet-listener
>                               port :stream :host interface ; misnamed in doc
>                               :reuse-address t :backlog 1))
>                     (warn "listening on ~S:~D fd=~D" interface port fd)
>                     (loop (mp:process-wait-until-fd-usable fd :input)
>                           (let ((new-fd (ext:accept-tcp-connection fd)))
>                             (warn "accepted new-fd=~D" new-fd)
>                             (unix:unix-fcntl new-fd unix:f-setfl unix:fndelay)
>                             (handle-connection new-fd))))
>                (when fd (unix:unix-close fd))))))
>     (mp:make-process #'listener
>                      :name (format nil "Listener on port ~D" port))))
>
>
> #||
> (setq $l1 (listen-for-connections))
> ;; clients connect to localhost 3128
> (mp::destroy-process $l1)
> ||#
>
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>
>