Custom History backend and Historical queries

Camunda 7 Topics Discussion & Questions
1

Hello,

I am attempting to create a new custom history backend by implementing HistoryEventHandler.
HistoryXXXQueries stops working since the History is no longer in the RDBMS. How do I point the historical queries to query the new backend instead of History RDBMS tables?

https://github.com/zalando-incubator/camunda-meets-cassandra and https://github.com/camunda/camunda-engine-hazelcast both changes the entire persistence engine.
We just want all the history data and queries in a separate backend, the runtime data stays as is.
Is there a way to just change the Historical queries interface to fetch data from the new backend?

We are using History queries to show the end-user the tasks that are already completed. We are specially interested in task instance history, Case instance history and CaseActInstance History.
The system creates around 6K cases per day leading to a 2 million+ cases per year.
Each case has around 500 business variables and 200+ human tasks, that are captured at various stages of the case-resolution process.

Please guide and advise how we can achieve this.

Thanks,
Subhro.

2

Do you want the history tables to be backed by another RDBMS server/instance or are you looking into other persistence models?

I think implementing a separate query infrastructure to access your custom backend may be possible but impractical. After adding a HistoryEventHandler it would probably include implementing

I haven’t done this, it’s just an idea of how it may work.

It may be more practical to introduce your history backend via a composite history event handler and reduce the history level of the default implementation to a level that is actually needed via the default query infrastructure.

To access your custom backend you’ll need to add your own query logic of course.

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