Multitenancy

[mat9819]

Hi Castore team !

Thank you for your great work on the library.

Is your feature request related to a problem? Please describe.
I am looking for a multitenancy event sourcing library.
How would you approach this in Castore ?

Describe the solution you'd like
I am not an expert of event sourcing but I would like to add to all events a tenantId property and modify the dynamodb event-storage-adapter in order to partition data by tenants.

Describe alternatives you've considered
One alternative is to create everything from scratch but I'd rather use your library.

Thank you very much for your help !

[ThomasAribart]

Hi @mat9819 and thanks for your interest !

I think that's an interesting feature so I'll add it to the roadmap. We could create a TenantizedEventStore that follows the EventStore interface while adding a tenantId argument for each method. And maybe modify the event storage adapter to expose a listTenants method ?

That's a lot of work and you're the only person having this need. We're a small team so we won't prioritize it for the next 6 months I think (we have more frequently asked subjects like snapshots and read models).

Two solutions that could do the trick right now:

1: Keep one event store and prefix your aggregate ids by a tenant id:

await eventStore.getAggregate(`${tenantId}#{aggregateId}`)

It will work but will degrade the performance of the listAggregateIds method for one tenant as you would have to list all the aggregate ids and filter manually the ones that begin by your tenantId. It should an acceptable tradeoff as listAggregateIds is mainly there for maintenance / migration jobs.

2: Suffix your event store by a tenant id

const tenantEventStore = new EventStore({
  eventStoreId: `POKEMONS#${tenantId}`
  ...
})

This solves the problem of the listAggregateIds but means that:

• You need a custom method outside of Castore to save/retrieve all your tenantIds
• In your code, you will construct an event store class each time you want to interact with one of your tenant data. So it will impact your backend performances.

I would rather go with the first solution.

Hope it helped ! Thanks for the issue !

[ThomasAribart]

@mat9819 there's actually a 3rd solution which is to create a new event store called tenant and join your data with message groups. See this page for an example: https://castore-dev.github.io/castore/docs/event-sourcing/joining-data/

[ThomasAribart]

Closing this as there's no plan to implement this in the near future.

[mat9819]

Hi Thomas,

Thank you very much for your answer !
I will look into your first solution.