hexpm VS oban

I was thinking of porting this library to Elixir. But first, I searched on hex.pm and Surprising. I found two packages that support merging tailwind classes: twix and tails

I often reference https://github.com/hexpm/hexpm which is the code behind hex.pm.

Feel free to take a look at the package manager and let me know if there are any libraries that you need that are missing. https://hex.pm/

I can assure you I'm not spending my time inventing new libraries. In the past 3 or so years of working in Elixir there have been maybe 2 or 3 cases where I was looking for a library and couldn't find a suitable one. Writing my own code to cover those cases took a few hours. This should hardly be a deal breaker for anyone if you take into account dozens, maybe even hundreds of hours the ecosystem could save you in the long run if your project is a good fit for it.

Before getting started you need to have both Elixir, the Hex package manager, the PostgreSQL relational database server and Node.js installed on your local computer to be able to follow through this guide.

We can then look at that function and see that ultimately it calls Supervisor.start_link(...) on a bunch of children. That means that one process's only job is to start up all those child processes and "supervise" them, meaning if any of them crash it will be notified and be able to handle that. I note that one of the processes runs the code in the module Hexpm.RepoBase which means it's in charge of managing database connections, and one runs the code in the module HexpmWeb.Endpoint which is the process in charge of managing the Phoenix side of things, handling incoming requests, spinning up new processes to handle each one, and directing them to the right controllers and stuff. Then there's a bunch of other modules listed, for things like rate limiting, billing reports, and other stuff. You can look in the codebase for those listed modules if you're interested, but the thing to note is that by putting the module name there, what happens is the supervisor will spawn a new process and run the start_link function of that module within that new process.

I was looking for a solution to run tests automatically every time I save any changes. The best way so far for me is the following hex package:

API server and website for Hex https://github.com/hexpm/hexpm

Dependency Current Latest Status bunt 0.2.0 0.2.0 Up-to-date cowlib 2.11.0 2.11.0 Up-to-date credo 1.6.1 1.6.3 Update possible db_connection 2.4.1 2.4.1 Up-to-date decimal 2.0.0 2.0.0 Up-to-date earmark_parser 1.4.19 1.4.20 Update possible postgrex 0.15.13 0.16.2 Update not possible To view the diffs in each available update, visit: https://hex.pm/l/AsY7q

Now it’s time to decide on a name for your package. In this guide I will be creating a new Ueberauth package. If you were to go on http://hex.pm and look at other Ueberauth packages, you notice there is a certain pattern followed. This will make the decision easy for us on what to call our Uberauth package that will implement the Patreon OAuth flow.

Go to the website https://hex.pm and search for the faker library to grab the latest version, so you can copy that to your mix config file, at the time of the making of this tutorial the latest version is 0.17.0, add the following to your project dependencies inside your mix.exs file:

Oban, backed by PostgreSQL or SQLite, also provides a queue-based job processing system. Exq, on the other hand, is backed by Redis. It provides features similar to Flume, but without built-in rate limiting and batch processing capabilities.

In Elixir land Oban[0] uses Postgres as queue and seems to work quite well.

[0] - https://github.com/sorentwo/oban

I hear you on that, and can say that Postgres is incredibly capable at going beyond typical relational database workloads. One example are durable queues that are transactionally consistent with the rest of the database play a unique role in our architecture that would otherwise require more ceremony. More details here: https://getoban.pro

We are also working on shifting some workloads off of Postgres on to more appropriate systems as we scale, like logging. But we intentionally chose to minimize dependencies by pushing Postgres further to move faster, with migration plans ready as we continue to reach new levels of scale (e.g. using a dedicated log storage solution like elastic search or clickhouse).

You can actually have "background jobs" in very different ways in Elixir.

> I want background work to live on different compute capacity than http requests, both because they have very different resources usage

In Elixir, because of the way the BEAM works (the unit of parallelism is much cheaper and consume a low amount of memory), "incoming http requests" and related "workers" are not as expensive (a lot less actually) compared to other stacks (for instance Ruby and Python), where it is quite critical to release "http workers" and not hold the connection (which is what lead to the creation of background job tools like Resque, DelayedJob, Sidekiq, Celery...).

This means that you can actually hold incoming HTTP connections a lot longer without troubles.

A consequence of this is that implementing "reverse proxies", or anything calling third party servers _right in the middle_ of your own HTTP call, is usually perfectly acceptable (something I've done more than a couple of times, the latest one powering the reverse proxy behind https://transport.data.gouv.fr - code available at https://github.com/etalab/transport-site/tree/master/apps/un...).

As a consequence, what would be a bad pattern in Python or Ruby (holding the incoming HTTP connection) is not a problem with Elixir.

> because I want to have state or queues in front of background work so there's a well-defined process for retry, error handling, and back-pressure.

Unless you deal with immediate stuff like reverse proxying or cheap "one off async tasks" (like recording a metric), there also are solutions to have more "stateful" background works in Elixir, too.

A popular background job queue is https://github.com/sorentwo/oban (roughly similar to Sidekiq at al), which uses Postgres.

It handles retries, errors etc.

But it's not the only solution, as you have other tools dedicated to processing, such as Broadway (https://github.com/dashbitco/broadway), which handles back-pressure, fault-tolerance, batching etc natively.

You also have more simple options, such as flow (https://github.com/dashbitco/flow), gen_stage (https://github.com/elixir-lang/gen_stage), Task.async_stream (https://hexdocs.pm/elixir/1.12/Task.html#async_stream/5) etc.

It allows to use the "right tool for the job" quite easily.

It is also interesting to note there is no need to "go evented" if you need to fetch data from multiple HTTP servers: it can happen in the exact same process (even: in a background task attached to your HTTP server), as done here https://transport.data.gouv.fr/explore (if you zoom you will see vehicle moving in realtime, and ~80 data sources are being polled every 10 seconds & broadcasted to the visitors via pubsub & websockets).

Hi HN!

This is something I've been tinkering on for the past couple months. It's basically just an API/CLI for scheduling delayed or recurring jobs as HTTP requests.

I initially built it as a personal tool to save myself a bit of time on little side projects where I've needed scheduled/recurring alerts, but decided it could be a good opportunity to practice building out a nice landing page [0] and documentation [1]. And who knows, maybe someone else will find it useful ¯\_(ツ)_/¯

The tool relies heavily on Elixir's Oban [2] library for managing jobs, and Mintlify [3] for documentation. I also shamelessly stole most of the frontend design from Resend [4] because I'm a fan of the aesthetic and thought it would be good for my design chops to use their design as a guide. I also discovered Radix [5] UI while working on this, which ended up being immensely helpful for moving quickly on the frontend.

Anyways, I almost certainly spent a bit too much time on small UX details that are most likely utterly inconsequential, but it was a fun exercise in polish :)

All feedback is welcome!

[0] https://www.booper.dev/

[1] https://docs.booper.dev/

[2] https://github.com/sorentwo/oban

[3] https://mintlify.com/

[4] https://resend.com/

[5] https://www.radix-ui.com/

Idk about pgagent but any table is a resilient queue with the multiple locks available in pg along with some SELECT pg_advisory_lock or SELECT FOR UPDATE queries, and/or LISTEN/NOTIFY.

Several bg job libs are built around native locking functionality

> Relies upon Postgres integrity, session-level Advisory Locks to provide run-once safety and stay within the limits of schema.rb, and LISTEN/NOTIFY to reduce queuing latency.

https://github.com/bensheldon/good_job

> |> lock("FOR UPDATE SKIP LOCKED")

https://github.com/sorentwo/oban/blob/8acfe4dcfb3e55bbf233aa...

> Bad code in a specific part of the codebase bringing down the whole app, as in our November incident.

This is a non-issue if you're using a Elixir/Erlang monolith given its fault tolerant nature.

The noisy neighbour issue (resource hogging) is still something you need to manage though. If you use something like Oban[1] (for background job queues and cron jobs), you can set both local and global limits. Local being the current node, and global the cluster.

Operating in a shared cluster (vs split workload deployments) give you the benefit of being much more efficient with your hardware. I've heard many stories of massive infra savings due to moving to an Elixir/Erlang system.

1. https://github.com/sorentwo/oban