Why DispatcherServlet Loading at first api call?

Flowable Engine
1

Why dispatcherServlet loading is not happening on application startup , instead it is getting loaded on first api call ?

2

Hi,

Lazy initialisation (on first request) is the default behaviour of Spring Boot for this Servlet.
If you want to change this behaviour you can control this with the property;

spring.mvc.servlet.load-on-startup=1

Why would you want to change this default behaviour?

This is all Spring related. Please check the Spring documentation for more info.

Regards,

Yvo

3

Reading your question again I need some more info.
There are several servlets that get initialized. For example; REST API dispatch servlets. And dispatch servlets for the UI APP itself.
Can you indicate what servlet(s) you are referring too? As the configuration can be different.

Yvo

4

There is class called FlowableServlet whose loadOnStartup is -1 meaning , intentionally made it to execute on first api call . I want to know what is benefit of making it on first api call and if the servlet loading happen through first api call , then it will be performance impact and overall average of api response will change

5

Hi,

You can configure the initialisation behaviour of the REST dispatch servlets by setting this property;

flowable.<engine>.servlet.load-on-startup

so for example;

flowable.process.servlet.load-on-startup=1

will initialise the BPMN REST API eagerly.

Have a look here for the available properties;

But; I’m not convinced of the fact this will give a noticeable performance benefit. The lazy init of the servlet dispatcher will add a minor performance impact on the first API request. But only the first. In my opinion a negligible impact looking at the total execution time when executing multiple requests.

Yvo

6

Thanks @yvo for the quick response.
Please help me in one of another doubt ,
If i make changes suggested by you , after that, is there will be issue in future ?
Or Is there any benefit of default behavhour that is loading servlet at the first api call ?
Or both behaviour is fine (eager and lazy)?

Mohit

7

With changes you mean setting certain properties?
I don’t see any issues now or in the foreseeable future.
Both behaviour is fine. There are marginal differences. Which approach is best depends on your use case.

8

Thank you @yvo for clarifying doubts , it will help me