[Glass] How to solve this problem - concurrency on one field/attribute

James Foster Smalltalk at JGFoster.net
Tue Aug 23 00:45:11 PDT 2022


Could you clarify your use of the word “session”? Is this an application session that crosses several Gems or is it a GemStone session (a single Gem)?


> On Aug 23, 2022, at 9:31 AM, Marten Feldtmann via Glass <glass at lists.gemtalksystems.com> wrote:
> I've face a problem for years now using Gemstone/S and I did several attempts to solve this, but I would like to ask, if there is a hidden trick to get rid of concurrency in this case using Gemstone/s.
> Think about a session object holding an attribute with a timestamp - a timestamp, where the last successful commit has been done in this session. Its a rough index about how the session hasn't done anything (regarding the read-only user case).
> This session object is shared in a Javascript ui frontend-application (actually the gop to the session) - and now whenever this ui calls an API function on the   server (resulting in a commit), the session object in the server gets updated. But if the UI now opens several windows and would like to do sevral independent stuff with the same session in  a concurrency way - you will notice, that the API calls might fail - due to concurrency of updating the same timestamp from different "logical" threads.
> How can this be solved in Gemstone/S ? Retry of the transaction just due to this field might be pretty cost intensive.
> How did I try to solve that in the past ?
> a) I added an update object in a work queue and and independent topaz process worked on that work queue
> In a newer attempt I introduced RabbitMQ in our solutions and use RabbitMQ for holding the information formerly stored in the work queue in Gemstone/S and now the topaz process receives information from RabbitMQ and updates the data in an optimized way. The good thing here is, that  I get session updates in an transaction with or without commit.
> Any ideas ?
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