I’d like to queue the mailing of an email via Bamboo but this code results in a Protocol.UndefinedError because it seems that Oban doesn’t know how to encode the %Bamboo.Email{} struct that contains the email body etc. Am I doing this correctly? If I am, I don’t understand why if Oban needs to encode the data which it’s about to queue. Wouldn’t every struct be unique and therefore there should be a way to handle this in the general case?
caller code:
defmodule Elijah.Emails do
import Bamboo.Email
use Bamboo.Phoenix, view: ElijahWeb.EmailView
alias Elijah.Accounts.Jobs.WelcomeEmail
@sender_no_reply {"Elijah", "no-reply@elijah.app"}
@supported_locales ~w(en)
def welcome_email(%{user: user, url: url}) do
base_email()
|> subject("Elijah - Welcome!")
|> to(user.email)
|> assign(:user, user)
|> assign(:url, url)
|> render_i18n(:welcome_email)
|> premail()
|> WelcomeEmail.new()
|> Oban.insert()
end
...
Oban job:
defmodule Elijah.Accounts.Jobs.WelcomeEmail do
use Oban.Worker, queue: :mailer, max_attempts: 4
@impl Oban.Worker
def perform(email, _job) do
# IO.inspect(email)
email
|> Elijah.Mailer.deliver_now()
:ok
end
end
Oban stores the job args in the db as json - so that job worker can retrieve them later
Jason rejects to converts a struct to json.
So just need to convert the struct to the map. Please note that if your struct is from ecto schema, the struct has more internal state and metadata for ecto…
There are two approaches
Pass minimal information to background job, and do the all thing in the background job
Pre-process as much as possible, and then pass only background job info to the queue
In most cases I prefer the former for following reasons
all work is in one function
your oban worker is very simple - just convert job args to value (with error handling, such as user is removed in the meantime) and call the function
it’s often easier to scale workers than the caller side (e.g. api side)
Here is a pattern I’m using:
defmodule MyEmails do
def welcome_email(%User{} = user, url) do
# actual job
end
end
defmodule MyEmailJob do
use Oban.Worker, queue: :email
def build(%User{id: user_id}, url), do: new(%{user_id: user_id, url: url})
def perform(%Oban.Job{args: %{"user_id" => user_id, "url" => url}}) do
user = MyApp.find_user!(user_id) # better to handle when user is already gone :)
MyEmails.welcome_email(user, url)
end
end
MyEmailJob.build(user, url) |> Oban.insert()
You can see:
context module does not need to know anything about oban
oban worker module is responsible to transfrom args between elixir app and oban
Whether to pass only reference or the full args - it really depends. For example, if you need the exact information when job is placed - then you should pass that information as job args, instead of delaying fetching them by job worker.
Yeah thanks for the detailed explanation. I get it now, Oban should be treated like a “pass-through”. I wasn’t quite understanding it’s design/usage but your reply helped a lot. The email worked.
For others with similar problems, here is my code.
def deliver_confirmation_instructions(user, url) do
WelcomeEmail.build(user.email, url) |> Oban.insert()
{:ok, %{to: user.email, url: url}}
end
defmodule Elijah.Accounts.Jobs.WelcomeEmail do
alias Elijah.Emails
use Oban.Worker, queue: :mailers, max_attempts: 4
def build(email, url), do: new(%{email: email, url: url})
def perform(%Oban.Job{args: %{"email" => email, "url" => url}}) do
Emails.welcome_email(%{email: email, url: url})
end
end
I have a Property struct with some nested structures with some tuples in them. It is, I think, cleaner to do this than to do a custom JSON encoder / decoder.
Note, that am pulling out the property.id and property.address for the Oban args so I can unique the job on property ID and inspect the address if something goes wrong.
I could store what I have of the property in the db first and reference it with the id, but I was unable to do that because of some other requirements. With this I’m able to just pass it around in Oban, and finally store it when I’m ready.
Not sure where this breaks down but it’s working for me for now.
