[Glass] Debugging a multiple process system ... ?

[Mariano Martinez Peck via Glass]

On Mon, Jan 22, 2018 at 3:14 PM, Marten Feldtmann via Glass <
glass at lists.gemtalksystems.com> wrote:

> Hmm,
>
> honestly I simply do not understand how this works :-(((((
>
> If I have an exception within my REST API calls I normally have to abort
> the transaction, so that nothing has changed ...  therefore how can I save
> a continuation into the database ??
>
> Its a shame I know, but I simply do not get it ...
>
>
> It's not a shame. I think the word "continuation" has been confusing since
several years already. And I think its confusing because of its association
with Seaside and the back button etc.
Let's talk about what it is for GemStone (well, at least what I understand
from it):

When an exception is signaled, and you read to an exception handler, from
the exception you can get the signaler context, right? That means that
somehow you have access the the stack that triggered that error (stack of
method context instances).  As far as I understand, the #callCC does
something *like* a deep copy of the stack. Its not a full 100% deep copy as
you might end up copying the whole extent. I guess there is a treshold
somewhere.

Once the continuation has been created (imageine you now have a kind of a
deep copy of the stack), then you are able to persist it as any other
persistent object. The object log is just one persistent object that makes
it easy to store this but it could be anywhere.

Then, you can simply open a debugger on a persisted continuation.

So... I imagine you can do something like this:



[

 " Your rest code here"
 ]
on: Error do: [ :ex |

   System abortTransaction.
Sytem beginTransaction.
    FaSmalltalkPlatform current saveExceptionContinuation: ex.
System commitTransaction.
]



Hope this is clearer...if not let me know. And maybe GemStone people may
have something to correct from what I said.


Best,




> Mariano Martinez Peck via Glass <glass at lists.gemtalksystems.com> hat am
> 22. Januar 2018 um 13:05 geschrieben:
>
>
> On Sun, Jan 21, 2018 at 1:35 PM, Dale Henrichs via Glass <
> glass at lists.gemtalksystems.com> wrote:
>
> Marten,
>
> Did you know that you should be able to open a debugger on a continuation
> - it is possible with tODE and GemTools. I think that most folks find this
> a reasonable solution.
>
>
>
> That's what I do. I do it at Seaside error handler as well as in some
> other error handlers (like background jobs).
>
> What I do is basically:
>
> -----
>
> [ self codeThatCouldTriggerErrorAndIWantToSaveAContinuationForLaterDebugging
> ]
> on: Error do: [ :ex |
>
>     FaSmalltalkPlatform current saveExceptionContinuation: exception.
> ]
>
> ----
>
> FaGemStonePlatform class >> saveExceptionContinuation: anException
>   | continuation action |
>   GRPlatform current canDebugInteractively
>     ifTrue: [ anException pass ].
>   GRPlatform current
>     logError: anException description
>     title: 'Continuation saved to object log'.
>   action := [ :cont |
>   continuation := cont.
>   #'create' ] callCC.
>   action == #'create'
>     ifTrue: [
>       | logEntry |
>       logEntry := WAObjectLogEntry
>         error: anException description
>         continuation: continuation. "the continuation is not resumable"
>       logEntry resumeContinuation.
>       logEntry addToLog.
>       ^ continuation ].
>   action == #'debug'
>     ifTrue: [ self halt ]
>
>
> That uses Grease which I would expect you have it loaded. WAObjectLogEntry
> is from Seaside but it's a very stupid subclass. so if you are not using
> Seaside you could just copy that class and give it whatever name and put it
> in your code.
>
> Once the continuation has been created and stored in the ObjectLog all you
> have to do is to connect with tODE and open a debugger on it.
>
> BTW, be sure to cleanup the object log as continuations are heavy:
> http://ws.stfx.eu/2LSEXBAMZT23
>
>
>
> --
> Mariano
> http://marianopeck.wordpress.com
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-- 
Mariano
http://marianopeck.wordpress.com
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