Multiple sagas (of same type) across different JVM using Axon

Yoann CAPLAIN :

How to actually manage sagas with multiple JVM of same app running

Should each JVM of this app use same database? Otherwise tracking tokens will not "be shared" across the same app?

How are events split among same app running for sagas? Does one saga type or saga instance always handled on same app (until it is shutdown so another instance take charge of it) ?

Or is each JVM receives events and each saga of same type will run? (and result in duplicate commands sent and errors)

Any other thing to care of?

Example of scenario: 3 same app on 3 different PC/VM. Saga of name "SagaA" which can start with EventA and end with EventB. Both events have a field "id", saga has 2 event handler to handle to events in the saga.

How will events be handled for example 3 events EventA and EventB, each with "id" of different value

Etc. Many more questions.

Steven :

A Saga in Axon terms is nothing more than a specific type of Event Handler. As such, Axon will use an Event Processor to give a Saga instance its events.

Event Processors come in two flavors:

SubscribingEventProcessor
TrackingEventProcessor

You should describe a subscribing processor as "receiving the events from the EventBus within the same JVM". A tracking processor should be described as "pulling events from the EventStore, keeping track of the progress through as shareable token.

The nature of your question now highly depends on which Event Processor is being used. With a SubscribingEventProcessor you would by definition not share the event load between different instances of the same app. Thus, a given Saga would be loaded on any live instance, given both receive events associated to the same saga. Needless to say, using the subscribing processor for Sagas does no work well if you are going to distributed the application running those Saga instances.

Instead, it is highly recommended to use a TrackingEventProcessor to be the source of events for a specific Saga instance. In doing so, any load sharing follows from the requirement that a TrackingToken must be claimed by such a processor to be able to do any work (aka, handling events). Thus, to share the workload of providing events from the event store to your Saga instances in Axon, you would have to do the following:

Set up a TrackingEventProcessor for said saga type
Set up a TokenStore, where the underlying storage mechanism is shared among all app instances
[Optional] If you want parallel processing of the event stream, you will have to segment the TrackingToken for the given saga type. [EDIT] On top of this, the saga_entry table used by the SagaStore should also be shared among among all app instances running the given Saga type

Hope this answer suffices for the "many more questions" you have @Yoann!

Guess you like

Origin http://43.154.161.224:23101/article/api/json?id=358516&siteId=1

Multiple sagas (of same type) across different JVM using Axon

Using global variables across multiple files in Python

Using Generic Type for same functionality

Database_SQL Knowledge_Update multiple records at the same time in a statement, using CASE WHEN (each record is updated to a different result)

RMarkdown: Multiple ggplots in same chunk using loop

Plusieurs sagas (de même type) entre les différentes JVM en utilisant Axon

[Spinning Up] python starts multiple scripts with different parameters at the same time

halcon template matching - matching multiple different objects at the same time

Multiple git accounts access different git repositories at the same time

[Solution] Add multiple directories in different parts of the same word document

CSS style - multiple identical tags at the same level with different styles

Is the performance of frequently adjusting an http request the same as that of multiple different http requests?

SpringBoot names but the same type of injection to achieve different Bean Spring container

Restful style, using the same address, different access methods

A different object with the same identifier using Spring data jpa with Hibernate

Solve the problem of using/displaying in different places on the same page if else

Dagger 2: Provide same instance between multiple Component with same Scope on different library modules

Axios requests the same interface multiple times at the same time (with different parameters), resulting in confusion in the returned data

How to configure multiple view resolvers of the same type in springmvc

py merges multiple nc files of the same type with regular names

springboot rabbitMq using multiple queues bound to the same switch

Is there a way to write multiple pandas dataframes to the same sheet using openpyxl engine?

In the test environment, the solution to conflicts caused by multiple users using the same environment

Multiple iterators (using enumerate) for the same iterable, what is going on?

Spring Boot with multiple data sources using same repositories and model classes?

Using a different host header name to set up multiple Web sites

Take different names from the same column using two different ID's from other table

Using DNS technology to map different domain names to different ports of the same IP

Why are two using clauses resolving to the same type seen as ambigious in gcc