Ash Elixir•3y ago

Setting Tenant when using Context Multitenancy

So I have configure my resources to use context multitenancy (Postgres Schemas). Migrations are working fine and creating an org creates an org schema as well. My question is how can I set the tenant, assuming am getting the tenant from the subdomain, which can the be used in Ash queries? I have seen Ash.set_tenant/1 which takes a map as argument, what does the map look like? How is it different from Ash.Query.set_tenant/2? An also there what's called Process Context is Ash, what is it and assuming it's a data structure stored in the Process dictionary, how does it look like? Examples or pseudo code will help. Hopefully my questions are making sense 😁

14 Replies

ZachDaniel•3y ago

You essentially have two options. 1. Provide the tenant when creating changesets (this is what I typically advise, but its a matter of preference). That looks like this:

Ash.Changeset.for_create(Resource, :create, .., tenant: "tenant_name")
Ash.Query.for_read(Resource, :read, .., tenant: "tenant_name")
Resource.code_interface_function(tenant: "tenant_name"

Ash.Changeset.for_create(Resource, :create, .., tenant: "tenant_name")
Ash.Query.for_read(Resource, :read, .., tenant: "tenant_name")
Resource.code_interface_function(tenant: "tenant_name"

2. Set the tenant into process context using Ash.set_tenant/1

Ash.set_tenant("tenant_name")
Ash.Changeset.for_create(Resource, :create, ..)
Ash.Query.for_read(Resource, :read, ..)
Resource.code_interface_function()

Ash.set_tenant("tenant_name")
Ash.Changeset.for_create(Resource, :create, ..)
Ash.Query.for_read(Resource, :read, ..)
Resource.code_interface_function()

The main thing about using the process dictionary is that you'll have to make sure you call Ash.set_tenant("tenant_name") in any processes you start

JmandaOP•3y ago

Thank you @Zach Daniel

ZachDaniel•3y ago

My pleasure 🙂

zimt28•3y ago

If I remember correctly set_tenant/1 expects a map, even though it should be a string It still works but ElixirLS will complain

ZachDaniel•3y ago

...weird

zimt28•3y ago

I think the typespec is wrong, but I cannot check right now

ZachDaniel•3y ago

fixed 🙂

zimt28•3y ago

But it would still be nice to have a callback somewhere that allows passing an actual tenant and converting it to a string in the callback

ZachDaniel•3y ago

Yeah, agreed that would be nice That would be a good first issue actually I'll make a ticket for it soon It would really just be a protocol you can implement, i.e

defimpl Ash.ToTenant do
  def to_tenant(%Org{short_name: name}), do: name
end

defimpl Ash.ToTenant do
  def to_tenant(%Org{short_name: name}), do: name
end

JmandaOP•3y ago

What's the equivalent of Triplex.exists?("tenant1") and Triplex.to_prefix(tenant) in Ash? And also if my resource is configured likes this:

postgres do
    ...
    manage_tenant do
      template ["org_", :id]
    end
  end

postgres do
    ...
    manage_tenant do
      template ["org_", :id]
    end
  end

it would nice if calling Ash.set_tenant/1 automatically adds the set prefix, for example Ash.set_tenant("tenant_1") results in {:tenant, org_tenant_1} instead of {:tenant, tenant_1}

ZachDaniel•3y ago

We don't actually have our own versions of those functions, you'll have to handroll them But to check if a tenant exists, you could either 1. lookup the org with that id, or 2. check if the schema exists using your ecto repo We could implement the to_tenant protocol automatically if you use manage_tenant in ash_postgres, which would solve for a lot of this. Just need to write the protocol.

JmandaOP•3y ago

That would be awesome

ZachDaniel•3y ago

I probably won't get to it soon though really. its a good first issue for someone else to tackle though, will write it up in a bit

JmandaOP•3y ago

In the meantime will just "handroll" my own, shouldn't be hard I have done it before 😁

Gaming

Programming

Setting Tenant when using Context Multitenancy

Did you find this page helpful?