When to use Stateful and Stateless sessions in drools?

[Nilima Gawade]

When to use Stateful and Stateless sessions in drools? How to use it in Microservices Architecture?

[Toshiya Kobayashi]

If an application (or a REST endpoint) recieves a request, evaluates it with drools and send a response, so it doesn't need to maintain drools session state, you can use a stateless session.

If an application (or a REST endpoint) recieves multiple requests and evaluates them together with drools, so it needs to maintain drools session state across requests, you need to use a stateful session.

Stateless session is recommended if possible, because it's easier to manage.

Microservices Architecture is generally based on stateless architecture, so stateless session.

Toshiya

2025年4月6日日曜日 15:36:25 UTC+9 nilima...@ebixcash.com:

[Nilima Gawade]

Thank you Toshiya.

Any thoughts on how to handle large data sets in case of of stateless session in microservices?

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[Toshiya Kobayashi]

> Any thoughts on how to handle large data sets in case of of stateless session in microservices?

Could you provide some more details? (e.g. One request has too large data which causes OutOfMemory. or Many concurrent requests etc.)

2025年4月9日水曜日 14:46:32 UTC+9 nilima...@ebixcash.com:

[Nilima Gawade]

1.If there are many concurrent requests?

2.Same rule will execute for say 1 million accounts lets say.

Thanks,

Nilima

To view this discussion visit https://groups.google.com/d/msgid/drools-usage/ef27990e-3317-495e-869d-348988b72040n%40googlegroups.com.

[Toshiya Kobayashi]

> 1.If there are many concurrent requests?

In stateless use case, each request is isolated, so you can easily scale your microservice (e.g. increase pods) depending on the load.

> 2.Same rule will execute for say 1 million accounts lets say.

It would be the same as the above case.

Cheers,
Toshiya

2025年4月14日月曜日 19:14:41 UTC+9 nilima...@ebixcash.com:

[Steven Chou]

Hi Toshiya,

When using the Rule Unit API, does it use Stateless or Stateful KIE session under the hood?

Thanks,

Steven

toshiyak...@gmail.com 在 2025年4月15日 星期二晚上9:36:01 [UTC-7] 的信中寫道：

[Ajay Chowdary Kandula]

• Rule Unit API uses a stateful KIE session model under the hood.
• It is designed for scenarios where rules need to react to changes in data over time, maintaining state and supporting inference, which are core features of stateful sessions.

If you need stateless, function-like rule execution, use the traditional `StatelessKieSession`. For encapsulated, stateful business logic, use Rule Units.

Thanks and Regards!!!
Ajay C. Kandula

maila...@gmail.com
+1-614-329-9276

To view this discussion visit https://groups.google.com/d/msgid/drools-usage/eeb7a40a-3dc9-4040-b08f-1f99584024afn%40googlegroups.com.

[Toshiya Kobayashi]

> When using the Rule Unit API, does it use Stateless or Stateful KIE session under the hood?

RuleUnitInstance is not exactly the same as StatefulKieSession, but similar to StatefulKieSession. You need to call "close" for RuleUnitInstance when your work is done.

If you close a RuleUnitInstance on every request, it would work as the same as the stateless use case.

2025年4月25日金曜日 3:27:48 UTC+9 chouc...@gmail.com: