Foreign key based multi-tenancy, allowing all the tenanted data to live in the same database.




Multi Tenancy Library - based on foreign key relationship


  • The package can be installed by adding ex_tenant to your list of dependencies in mix.exs:
def deps do
    {:ex_tenant, "~> 0.1.1"}
  • Run: mix deps.get && mix deps.compile to retrieve dependencies & compile

How to use the library

  • Call the use ExTenant macro to inject all the required behaviour into your
  • Application Repo module to enable all multi-tenancy functions.


In the application Config file the repo and tenanted_field settings need to be configured. ExTenant will default the tenanted_field setting to be tenant_id.


  config :ex_tenant,
    tenant_repo: MyAppRepo,
    tenanted_field: "tenant_id",
    get_tenant_from_subdomain_func: &your_application_get_tenant_from_subdomain_function/1
  • If the repo is not configured ExTenant will raise an exception.
  • the get_tenant_from_subdomain_func is optional if you decide to use the Plug - see example below


  • In your application Repo file call the use macro as per this example
  def YourApplication.Repo do
    use ExTenant,
      config: [
        otp_app: :name_of_your_elixir_phoenix_app_as_atom,
        adapter: Ecto.Adapters.Postgres,
        tenanted_field: "tenant_id"

In order to get the tenant_id into the progress dictionary in Phoenix we recommend to use a plug - there you should retrieve the tenant name from something like the sub domain in the url. Then using the tenant name retrieve the tenant, and call:

  • Repo.put_tenant_id(tenant_id)

To insert the tenant_id into the process dictionary.


  • An example of how a Plug can be used to insert the tenant_id into the process dictionary

  • Take a look at the module ExTenant.SubdomainPlug

From here all your Repo callbacks (Repo.get/ etc) will have a where clause applied to them with the tenant_id injected into the clause.

In order to set the tenant_id on insert and update functions the tenant_id needs to be inserted into the attributes to be inserted. The tenanted_schema macro & the tenanted() function inserts the correct belongs_to tenanted foreign key based relationship.

Further the cast_tenant method overloads the standard Ecto.Changeset.cast function by injecting the tenant_id into the params and allowed keys. This function raises exceptions when the Repo was not configured correctly in config.exs and also if the tenant_id value is not set in the process_dictionary.

Ecto Schema/Changeset

  defmodule Post do
    use ExTenant.Schema
    use ExTenant.Changeset

    tenanted_schema "posts" do
      field(:name, :string)
      field(:body, :string)


    defp changeset(attrs) do
      |> cast_tenanted(params, [:name, :body])

NB: If the tenant_id is not set in the changeset, Repo.insert/update callbacks will raise a Postgrex.Error (not_null_violation)


  • documentation to be added.

Features for Querying the database

  • Overrides the Ecto callback default_options to inject the tenant_id
  • Overrides the Ecto callback prepare_query to inject the tenant_id into a where clause