[GemStone-Smalltalk] [GBS] How often does this error affect you?

Dennis Smith dennis at cherniaksoftware.com
Wed May 14 09:15:15 PDT 2014

If I understand correctly, the problem occurs if the old class is 
connected to the class on the client side?
Then migrate generates an error?

We have a tool UI with a migrate button which logs out and in THEN does 
the migrate.

On 2014-05-14 11:44 AM, Richard Sargent wrote:
> If you have a class in your client image mapped to the latest (or only)
> version of a server class, creating a new version of the server class will
> result in replication errors until you reconnect the client class to the new
> server class version.
> GBS is designed to automatically migrate instances of older versions of a
> server class to the version that the client is connected to when you
> replicate such an instance. This is the "skew" case.
> The problem case is the anti-skew, in which the automatic migration - if it
> were to happen - would have migrated instances of newer versions of the
> class to older versions. GBS throws an error. This error can arise as soon
> as you change the class definition and agree to "commit and migrate", if you
> already have an instance of the class replicated into the client image. It
> can also occur at any point following this event, if any subsequent
> replication tries to bring back an object graph referencing an instances of
> the new class version.
> The error is a GbsClassGenerationError. It will occur more frequently
> starting with server version 3.2, since we corrected the problem of #become:
> not notifying the GCI client (GBS in this case) of the change. Migration of
> instances to the new class version uses #become:.
> There are two workarounds to the error. One is to log out and back in again.
> The second is to use the Connector Browser and reconnect the class to the
> server. (The browser would show the class as disconnected, since the class
> is mapped to an older version, rather than the latest version of the named
> class.)
> We would appreciate your feedback on how much of a problem this has been for
> you in the past, and if you have started to upgrade to 3.2, how much it
> impacts you now. Additionally, feedback on how you would like GBS to handle
> this case (other than "don't throw an error") would help us determine what
> we need to do.
> Thank you,
> Richard Sargent
> --
> View this message in context: http://forum.world.st/GBS-How-often-does-this-error-affect-you-tp4759041.html
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Dennis Smith
Cherniak Software Development Corporation
416.798.7948  x208

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