# Queuetopia
[](https://github.com/annatel/queuetopia/actions) [](https://github.com/annatel/queuetopia/issues) [](http://opensource.org/licenses/MIT) [](https://hex.pm/packages/queuetopia) [](https://hex.pm/packages/queuetopia)
A persistant blocking job queue built with Ecto.
#### Features
- Persistence — Jobs are stored in a DB and updated after each execution attempt.
- Blocking — A failing job blocks its queue until it is done.
- Dynamicity — Queues are dynamically defined. Once the first job is created
for the queue, the queue exists.
- Reactivity — Immediatly try to execute a job that has just been created.
- Retries — Failed jobs are retried with a configurable backoff.
- Persistence — Jobs are stored in a DB and updated after each execution attempt.
- Performance — At each poll, only one job per queue is run. Optionnaly, jobs can
avoid waiting unnecessarily. The performed job triggers an other polling.
- Isolated Queues — Jobs are stored in a single table but are executed in
distinct queues. Each queue runs in isolation, ensuring that a job in a single
slow queue can't back up other faster queues and that a failing job in a queue
don't block other queues.
- Handle Node Duplication — Queues are locked, preventing two nodes to perform
the same job at the same time.
## Installation
Queuetopia is published on [Hex](https://hex.pm/packages/queuetopia).
The package can be installed by adding `queuetopia` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:queuetopia, "~> 1.1.2"}
]
end
```
After the packages are installed you must create a database migration to
add the queuetopia tables to your database:
```bash
mix ecto.gen.migration create_queuetopia_tables
```
Open the generated migration in your editor and call the `up` and `down`
functions on `Queuetopia.Migrations`:
```elixir
defmodule MyApp.Repo.Migrations.CreateQueuetopiaTables do
use Ecto.Migration
def up do
Queuetopia.Migrations.V1.up
end
def down do
Queuetopia.Migrations.V1.down
end
end
```
Now, run the migration to create the table:
```sh
mix ecto.migrate
```
## Usage
### Defining the Queuetopia
A Queuetopia must be informed a repo to persist the jobs and a performer module,
responsible to execute the jobs.
Define a Queuetopia with a repo and a perfomer like this:
```elixir
defmodule MyApp.MailQueue do
use Queuetopia,
repo: MyApp.Repo,
performer: MyApp.MailQueue.Performer
end
```
Define the perfomer, adopting the Queuetopia.Jobs.Performer behaviour, like this:
```elixir
defmodule MyApp.MailQueue.Performer do
@behaviour Queuetopia.Jobs.Performer
@impl true
def perform(%Queuetopia.Jobs.Job{action: "do_x"}) do
do_x()
end
defp do_x(), do: {:ok, "done"}
end
```
### Start the Queuetopia
An instance Queuetopia is a supervision tree and can be started as a child of a supervisor.
For instance, in the application supervision tree:
```elixir
defmodule MyApp do
use Application
def start(_type, _args) do
children = [
MyApp.MailQueue
]
Supervisor.start_link(children, strategy: :one_for_one)
end
end
```
Or, it can be started directly like this:
```elixir
MyApp.MailQueue.start_link()
```
The configuration can be set as below:
```elixir
# config/config.exs
config :my_app, MyApp.MailQueue,
poll_interval: 60 * 1_000,
repoll_after_job_performed?: true,
disable?: true
```
Note that the polling interval is optionnal.
By default, it will be set to 60 seconds.
### Feeds your queues
To create a job defines its action and its params and configure its timeout and the max backoff for the retries.
By default, the job timeout is set to 60 seconds, the max backoff to 24 hours and the max attempts to 20.
```elixir
MyApp.MailQueue.create_job("mails_queue_1", "send_mail", %{email_address: "toto@mail.com", body: "Welcome"}, [timeout: 1_000, max_backoff: 60_000])
```
So, the mails_queue_1 was born and you can add it other jobs as we do above.
You can wake up the scheduler to run the next pending jobs by calling the `send_poll/0` function.
```elixir
MyApp.MailQueue.send_poll()
```
### One DB, many Queuetopia
Multiple Queuetopia can coexist in your project, e.g your project may own its Queuetopia and uses a library
shipping its Queuetopia. The both Queuetopia may run on the same DB and share the same repo. They will have a different scheduler,
may have a different polling interval. They will be defined a scope to reach only their own jobs,
so the won't interfer each other.
## Test
Rename env/test.env.example to env/test.env, set your params and source it.
```sh
MIX_ENV=test mix do ecto.drop, ecto.create, ecto.migrate
mix test
```
Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
be found at [https://hexdocs.pm/queuetopia](https://hexdocs.pm/queuetopia).
Thanks to [Oban] [https://github.com/sorentwo/oban] and elixir community who inspired the Queuetopia development.
