Hello!
Just want to share my experience with you.
Maybe it will save some hours for somebody.
I have 2 applications in umbrella application:
- Secutity
- Store
Application Security can be used in other projects.
Each application has its own repository, configured to the same database (Store is sharing Security functional):
repo_transaction_umbrella/config/dev.exs:
use Mix.Config
config :security, Security.Repo,
adapter: Ecto.Adapters.Postgres,
username: "postgres",
password: "postgres",
database: "repo_transaction_umbrella_dev",
hostname: "localhost",
pool_size: 10
config :store, Store.Repo,
adapter: Ecto.Adapters.Postgres,
username: "postgres",
password: "postgres",
database: "repo_transaction_umbrella_dev",
hostname: "localhost",
pool_size: 10
repo_transaction_umbrella/apps/security/lib/security/contexts/user.ex:
defmodule Security.User do
alias Security.{Repo, UserSchema}
def add(params) do
changeset = UserSchema.build_changeset(%UserSchema{}, params)
Repo.insert(changeset)
end
end
repo_transaction_umbrella/apps/store/lib/store/contexts/profile.ex:
defmodule Store.Profile do
alias Store.{Repo, ProfileSchema}
def add(params) do
changeset = ProfileSchema.build_changeset(%ProfileSchema{}, params)
Repo.insert(changeset)
end
end
repo_transaction_umbrella/apps/store/lib/store/contexts/customer.ex:
defmodule Store.Customer do
alias Ecto.Multi
alias Store.{Repo, Profile}
alias Security.User
def add(params) when is_map(params) do
multi =
Multi.new
|> Multi.run(:user, fn _ -> User.add(params) end)
|> Multi.run(:profile, fn %{user: user} ->
params
|> Map.put_new("user_id", user.id)
|> Profile.add()
end)
case Repo.transaction(multi) do
{:ok, result} -> {:ok, result}
{:error, :user, changeset, %{}} -> {:error, :user, changeset}
{:error, :profile, changeset, %{}} -> {:error, :profile, changeset}
end
end
end
I try to add new customer with Store.Customer.add/1 and incorrect parameters (name is empty):
iex(1)> params = %{"username" => "user_1", "name" => ""}
%{"name" => "", "username" => "user_1"}
iex(2)> alias Store.Customer
Store.Customer
iex(3)> Customer.add(params)
19:16:00.727 [debug] QUERY OK db=0.3ms
begin []
19:16:00.765 [debug] QUERY OK db=3.6ms
INSERT INTO "security"."users" ("username","inserted_at","updated_at") VALUES ($1,$2,$3) RETURNING "id" ["user_1", {{2017, 1, 27}, {16, 16, 0, 745833}}, {{2017, 1, 27}, {16, 16, 0, 753016}}]
19:16:00.768 [debug] QUERY OK db=0.4ms
rollback []
{:error, :profile,
#Ecto.Changeset<action: :insert, changes: %{user_id: 110},
errors: [name: {"can't be blank", [validation: :required]}],
data: #Store.ProfileSchema<>, valid?: false>}
Looks ok - transaction started, insert ok, then rollback (because second insert failed).
But, in fact, ROLLBACK did nothing with this INSERT.
Reason - separate Repo configuration, separate sessions in PostgreSQL.
Log statement from postgresql.conf helped to figure it out:
repo_transaction_umbrella_dev_(postgres)_[BEGIN]_{00000}_14/6LOG: execute POSTGREX_BEGIN: BEGIN
repo_transaction_umbrella_dev_(postgres)_[INSERT]_{00000}_30/6LOG: execute <unnamed>: INSERT INTO "security"."users" ("username","inserted_at","updated_at") VALUES ($1,$2,$3) RETURNING "id"
repo_transaction_umbrella_dev_(postgres)_[INSERT]_{00000}_30/6DETAIL: parameters: $1 = 'user_1', $2 = '2017-01-27 15:56:00.280901', $3 = '2017-01-27 15:56:00.287823'
repo_transaction_umbrella_dev_(postgres)_[ROLLBACK]_{00000}_14/6LOG: execute POSTGREX_ROLLBACK: ROLLBACK
We started transaction with BEGIN in session 14, then did INSERT in session 30, then ROLLBACK in session 14.
Because Store.Customer.add/1 executes Security.User.add/1 (Security.Repo) and Store.Profile.add/1 (Store.Repo) in transaction from Store.Repo.
The solution is simple - pass the same Repo as you are using for Repo.transaction to functions as parameter if there are functions with different repo configurations in your transaction:
repo_transaction_umbrella/apps/security/lib/security/contexts/user.ex:
defmodule Security.User do
alias Security.{Repo, UserSchema}
def add(params) do
changeset = UserSchema.build_changeset(%UserSchema{}, params)
Repo.insert(changeset)
end
def add(params, repo) do
changeset = UserSchema.build_changeset(%UserSchema{}, params)
repo.insert(changeset)
end
end
repo_transaction_umbrella/apps/store/lib/store/contexts/profile.ex:
defmodule Store.Profile do
alias Store.{Repo, ProfileSchema}
def add(params) do
changeset = ProfileSchema.build_changeset(%ProfileSchema{}, params)
Repo.insert(changeset)
end
def add(params, repo) do
changeset = ProfileSchema.build_changeset(%ProfileSchema{}, params)
repo.insert(changeset)
end
end
repo_transaction_umbrella/apps/store/lib/store/contexts/customer.ex:
defmodule Store.Customer do
alias Ecto.Multi
alias Store.{Repo, Profile}
alias Security.User
def add(params) when is_map(params) do
multi =
Multi.new
|> Multi.run(:user, fn _ -> User.add(params, Repo) end)
|> Multi.run(:profile, fn %{user: user} ->
params
|> Map.put_new("user_id", user.id)
|> Profile.add(Repo)
end)
case Repo.transaction(multi) do
{:ok, result} -> {:ok, result}
{:error, :user, changeset, %{}} -> {:error, :user, changeset}
{:error, :profile, changeset, %{}} -> {:error, :profile, changeset}
end
end
end
I have loaded this test umbrella application to GitHub.
I don’t think we can warn as you can do anything you want in the anonymous function. You could even call the repository dynamically. An implementation would be quite complex and require an unecessary central coordination for repos.
