[racket] distributed places - throwing dcgm-type contract violation on *channel-get

Thanks, but ssh is set up correctly. If not, racket typically complains 
that it cannot connect to the remote node, rather than throwing the 
contract violation.  In fact, with both the remote and the localhost, I 
can see the new spawned racket process running.   I get the error on 
*channel-get and only when the remote process has already put something 
on the channel.

On 12/16/2012 11:46 AM, Michael Wilber wrote:
> This is just a shot in the dark, but do you have your SSH keys set up?
> If you get a password prompt when you 'ssh remote-node-name', I think it
> might not work.
>
> (From the looks of things, since you're spawning a node on localhost, I
> think you might have to get 'ssh localhost' working the same way. Maybe
> something like cat .ssh/id_rsa >> .ssh/authorized_keys might help?)
>
> Matthew Eric Bassett <mebassett at gegn.net> writes:
>> Kevin,
>>
>> Thanks again for your time looking into this - hope the dissertation
>> edits are going well. :)
>>
>> Some clarification after I tried it this morning:  Invoking racket (with
>> "-W debug", thanks for the tip!) on your hello-world-place.rkt hangs at
>> the following:
>>
>> SPAWNED-PROCESS:2865 (/usr/bin/ssh localhost /usr/local/bin/racket -lm
>> racket/place/distributed/launch spawn 7000)
>> try 0 waiting 1 sec to retry connection to localhost:7000
>>
>>   From the racket repl I tried the following:
>>
>>   >(define-values (node pl) (spawn-node-supervise-place-at "localhost"
>> #:listen-port 7000 "hello-world-place.rkt" 'hello-world))
>>   >(*channel-put pl "hello")
>>   >(*channel-get pl)
>> ; dcgm-type: contract violation
>> ; expected: dcgm?
>> ; context...: ;
>> /usr/local/lib/racket/collects/racket/place/distributed.rkt:436:8: loop
>> ; /usr/local/lib/racket/collects/xrepl/xrepl.rkt:1342:0
>> ; /usr/local/lib/racket/collects/racket/private/misc.rkt:87:7
>>
>> Thanks,
>>
>> Matthew
>>
>>
>>
>> On 12/15/2012 10:22 PM, Matthew Eric Bassett wrote:
>>> Kevin,
>>>
>>> Many thanks for your response.
>>>
>>> The only significant difference between your code and mine is the use
>>> of localhost (which makes distributed places a lot less distributed)
>>> and the port specification.  In any case, I've tried your code
>>> verbatim on two machines now.  It also throws the same dcgm contract
>>> violation.
>>>
>>> What OS are you running?  Perhaps there's something funny about my
>>> build?  I don't know anything about distributed/places internals here,
>>> I'm just guessing.
>>>
>>> I've tested this on Fedora 17 x64, and on an amazon stock x64 ec2
>>> machine.
>>>
>>> Regards,
>>>
>>> Matthew Eric
>>>
>>> On 12/15/2012 04:05 AM, Kevin Tew wrote:
>>>> The following thunk example works for me.
>>>> Uncommenting the message-router line will pump back stdout and stderr
>>>> from the remote node so you can see any errors that may be occurring
>>>> at the remote-node.
>>>> You will have to kill the message router by hitting CTRL-C when you
>>>> want to end the program.
>>>>
>>>>
>>>> EXAMPLE 1
>>>> -----------------------------------------
>>>> #lang racket
>>>> (require racket/place/distributed)
>>>> (define (hello-world)
>>>>    (place ch
>>>>      (printf/f "hello-world received: ~a\n" (place-channel-get ch))
>>>>      (place-channel-put ch "Hello World\n")
>>>>      (printf/f "hello-world sent: Hello World\n")))
>>>> (provide hello-world)
>>>>
>>>> (module+ main
>>>>    (define-values (node pl) (spawn-node-supervise-place-at "localhost"
>>>> #:listen-port 7000 "hello-world-place.rkt" 'hello-world #:thunk #t))
>>>>    (*channel-put pl "Hello bozo")
>>>>    (*channel-get pl)
>>>>    #;(message-router node)
>>>>    )
>>>>
>>>>
>>>> Example 2 show how I would normally write distributed places code
>>>> without using the #:thunk keyword argument.
>>>>
>>>> EXAMPLE 2
>>>> --------------------------------------------
>>>> #lang racket
>>>> (require racket/place/distributed)
>>>> (define (hello-world ch)
>>>>    (printf/f "hello-world received: ~a\n" (place-channel-get ch))
>>>>    (place-channel-put ch "Hello World\n")
>>>>    (printf/f "hello-world sent: Hello World\n"))
>>>> (provide hello-world)
>>>>
>>>> (module+ main
>>>>    (define-values (node pl) (spawn-node-supervise-place-at "localhost"
>>>> #:listen-port 7000 "hello-world-place.rkt" 'hello-world))
>>>>    (*channel-put pl "Hello bozo")
>>>>    (*channel-get pl)
>>>>    #;(message-router node)
>>>>    )
>>>>
>>>>
>>>> On 12/15/2012 02:16 AM, Matthew Eric Bassett wrote:
>>>>> Just to update, also tried this on v5.3.1 using
>>>>> spawn-node-supervise-place-at with #:thunk set. same result.
>>>>>
>>>>> On 12/14/2012 03:31 PM, Matthew Eric Bassett wrote:
>>>>>> Hey folks,
>>>>>>
>>>>>> I was playing around with distributed places and I ran into a some
>>>>>> problems.  I'm using racket v5.3 and am following the docs from the
>>>>>> racket reference
>>>>>> (http://docs.racket-lang.org/reference/distributed-places.html)
>>>>>>
>>>>>> Let's say we have an example just like the one in the reference.
>>>>>>
>>>>>> hello-world-place.rkt
>>>>>> ----------------------
>>>>>> (define (hello-world)
>>>>>>      (place ch (printf "hello-world received: ~a\n"
>>>>>> (place-channel-get ch))
>>>>>>      (place-channel-put ch "Hello World\n")
>>>>>>      (printf "hello-world sent: Hello World\n")))
>>>>>>
>>>>>> Then from the racket xrepl we do
>>>>>>
>>>>>>>> (define-values (node pl)
>>>>>>              (spawn-node-supervise-dynamic-place-at remote-node
>>>>>> "hello-world-place.rkt" 'hello-world))
>>>>>> ; there's now a racket process running on my remote-node
>>>>>>>> (*channel-put pl "hi")
>>>>>> ; the remote node shuts down as we expect, giving the
>>>>>> place-channel-get should have locked it until this point.
>>>>>>>> (*channel-get pl)
>>>>>> ; dcgm-type: contract violation
>>>>>> ;   expected: dcgm?
>>>>>> ;   given: #<eof>
>>>>>> ;   context...:
>>>>>> ;
>>>>>> /usr/local/lib/racket/collects/racket/place/distributed.rkt:442:8:
>>>>>> loop
>>>>>> ;    /usr/local/lib/racket/collects/xrepl/xrepl.rkt:1341:0
>>>>>> ; /usr/local/lib/racket/collects/racket/private/misc.rkt:87:7
>>>>>>
>>>>>> I've tried [naively] using place-channel-put/get instead of
>>>>>> *channel-put/get, same result.  Wrapping it in a message-router
>>>>>> makes no difference.
>>>>>>
>>>>>>>> (message-router node (after-seconds 2 (*channel-put pl "hi!")
>>>>>> (*channel-get pl)))
>>>>>> ; gives same result as above.
>>>>>>
>>>>>> Any ideas what I'm doing wrong or what I'm missing?
>>>>>>
>>>>>> Many thanks,
>>>>>>
>>>>>>
>>>>>
>>>
>>
>> --
>> Matthew Eric Bassett |http://mebassett.info
>>
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-- 
Matthew Eric Bassett | http://mebassett.info