Taskmanager: rethink implementation

[henning-gerhardt]

Current taskmanager (2.x and 3.x) implementation is a self written, in parts non error free (see #4135 ) or need some improvements (see #4136 ) and did not have any kind of unit or integration tests. Maybe ReactiveX/RxJava could be a possible replacement for a future and more advantage usage.

[matthias-ronge]

Production 3 uses the Camunda workflow editor. Perhaps it would make sense to also use the Camunda workflow engine instead of the existing code.

[henning-gerhardt]

Please do not mix up different things. If internal workflow engine should be replaced then open a new issue for this!

[matthias-ronge]

I see the automatic tasks and their display in the task manager as part of the workflow engine. It's just the question of whether you just rewrite the task manager (with ReactiveX/RxJava you would also have to write your own code, as I understand it) or whether you replace the entire workflow engine, which then also brings its own automatic task processor with it. I think we have to think about that, if we approach this topic.

[henning-gerhardt]

As in the past the Camunda workflow editor was evaluated even the Camunda workflow engine was evaluated and this engine could not provide all needed features and a migration from own to Camunda engine was not possible without to lost everything. Replacing the workflow engine is a different discussion and effects only the taskmanager. This could mean that an other engine deliver a taskmanager like tool and so this tool can replace the current taskmanager.

[matthias-ronge]

If the Camunda workflow engine cannot do that, then you are certainly right. It would have been great if there had been a ready-made package that could process the workflow file. So we have to write code again with the new framework.

By the way, I could well imagine a separation here, that the workflow engine runs independently as a daemon on the system. Then you could also restart Tomcat without compromising the processing. We would have to think again in detail, I just wanted to leave the thought here.

[BartChris]

Maybe worth a look: https://github.com/jobrunr/jobrunr