GoodJob – a Postgres-based ActiveJob back end for Ruby on Rails

https://island94.org/2020/07/introducing-goodjob-1-0

by another-dave • 6 years ago

178 92 6 years ago

island94.org

simplify3• 6 years ago

This is the exact sort of thing I love about the Rails community. Always innovating to keep things simple.

another-dave• 6 years ago

It would be nice to have one less dependency in the tech stack but honestly have no complaints with Sidekiq so far.

I'm quite new to Ruby/Rails though — would be interesting to hear from others how they think it stacks up (unfortunately the author doesn't compare in the blog post)

dyeje• 6 years ago

Yea I agree, a comparison to sidekiq would be helpful in evaluating and was what I was expecting to be covered on the page.

simplify3• 6 years ago

Agreed, Sidekiq is great and I don't imagine anyone switching away from it for existing projects.

But I can see GoodJob being better for spinning up new projects, as there are fewer moving parts to worry about, and it's easy to upgrade to Sidekiq, etc. when you need to (thanks to ActiveJob's standard abstraction).

cactus20932• 6 years ago

The standard advice used to be that neither Redis or Postgres are very good for using as a queue.

The creator and former maintainer of Redis was up until a few years ago discouraging its use as a queue, I think mainly because of its lack of durability and high availability at the time. He built a prototype Disque[0] to address the issues but it never became production ready. The other downside is that Redis is in-memory which means the queues have less capacity/are more expensive for the same capacity than an on-disk solution, but as memory gets cheaper over the years this becomes less and less of an issue. The upside is the throughput of Redis is very high.

I have personally worked on rails apps using redis-based queues like resque (and to a lesser extent sidekiq), and actually haven't run into any redis crashes or downtime in years of runtime, redis is very solid in general. You can also snapshot the redis instance periodically, to limit the number of jobs you would lose if it did crash.

In terms of using a primary db like postgres or mysql as a queue, I have personally run into issues with this multiple times. I would recommend never to do it, except on the smallest of side projects.

The issue is that eventually your queues will back up, whether it's due to a bug, surge of traffic, or just complex interaction of behavior in your app that cascades a ton of jobs at once when you run a backfill or something. When your app starts to get overloaded it's pretty trivial to increase the number of web instances running, so your bottleneck in these situations is going to be the db performance. As your queues get backed up, your queue workers are running at full speed processing jobs nonstop, which puts strain on your DB. Additionally, the act of enqueueing and dequeuing a job itself also puts strain on the db, so you can easily get into an unstable situation where each job that gets added to the queue makes every other job take longer.

If you allocate a separate DB instance that is only running your queue, that is much safer. Still, a DB like postgres is not great at doing constant writes and deletes, it creates additional auto-vacuum pressure for instance. But this will manifest as just getting worse throughput on the same hardware than you could get from a dedicated queue like rabbit mq, so if you're not at large scale it's a fine option.

Edit: And one other thing to add, for a lot of web apps the scope of what is needed from a queue these days is a lot less now than it was in the past. It used to be, and in large enterprise systems it often still is, the case that when people talked about a message queue they wanted something to facilitate passing messages between many completely separate apps. Now most apps just use a rest api for that (or perhaps protobufs or graphql or something but still over http). So I think historically an additional reason against using a simple datastore as a queue was that it didn't have enough features so you'd end up re-inventing the wheel with things like brokers, fan out and broadcast patterns, at-most-once vs at-least-once semantics, etc. But here I'm just considering the very limited usecase of a sidekiq-like queue, for processing jobs in the background for a single web app.

tl;dr: Never use your primary DB as a queue. Using a separate Postgres instance can work if you over-provision capacity and don't need to maximize throughput, and a Redis-based solution can work if you don't need high availability and can tolerate some messages lost if something goes wrong.

[0] https://github.com/antirez/disque

learc833• 6 years ago

That completely depends on the amount of items you plan on adding to the queue. I’ve used the primary DB as a queue often over the last 10 years for things like sending notifications.

Sure there’s a point where this doesn’t make sense, but for the majority of cases there are ways to mitigate the positive reinforcement loop you’re taking about.

The easiest is to limit the number of workers to some number that won’t impact DB performance if they are running full tilt. You can even use an enum on existing records to determine the background job status if you have few enough rows (we do this for a table with a few hundred thousand job applicants).

I’ve found that in most cases we want a record that the background job was performed, so we were often updating the database anyway when a job was complete.

Sure if you are firing off so many events that PG can’t keep up with writing them, then PG isn’t a good option.

pselbert• 6 years ago

Never use your primary DB as a queue. Using a separate Postgres instance can work if you over-provision capacity and don't need to maximize throughput, and a Redis-based solution can work if you don't need high availability and can tolerate some messages lost if something goes wrong.

That is a broad generalization that assumes most applications are operating at mega scale. The benefits of simplified dependencies (a single database instance), transactional guarantees (a single database instance) and persistence (not using Redis) far outweigh the eventual possibility that the queue will place too large a load on your database.

As the author of Oban[0] (an PG backed persistent queue in Elixir) I'm definitely biased. However, the level of adoption in the Elixir community seems to signal that a lot of companies favor simplicity and safety over a possible scale issue down the road. The primary application I work on processes ~500k-1m jobs a day and the queue overhead is virtually invisible.

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

debaserab22• 6 years ago

In terms of using a primary db like postgres or mysql as a queue, I have personally run into issues with this multiple times. I would recommend never to do it, except on the smallest of side projects.

Postgres is fine as a queue for medium to large sized projects as it depends completely on your workload and what sort of performance characteristics you need. Thinking about it in terms of project size is the wrong way to evaluate it.

philwelch2• 6 years ago

I have experienced this lifecycle many times:

1. Ah, we’re using the database as a queue.

2. Database is running hot, I wonder where all the load is coming from?

3. Oh, it’s all the queue tables.

It’s not even a scale/load issue. Even at smaller scales you’re introducing some major lock contention.

chriszhu12• 6 years ago

Another small thing to consider: Adding redis to your stack adds a new failure mode. A service I built a while ago was running on Heroku where Redis add-ons aren't cheap, and our Redis would always running against memory limits, which would cause our entire service to fail.

Meanwhile, 250GB Postgres server has been churning along no problem.

Also, conceptually, architecture where state = DB, and business logic = web server is generally easier to reason about during service migrations and such.

If you don't use ActionCable which I think is the other core feature that relies on Redis, being able to remove it would've saved me a lot of early morning firefighting.

debaserab22• 6 years ago

This is exactly why I stuck with DelayedJob after all of these years. The community seemed to flock to Resque or Sidekiq, but I always felt my needs were met just fine with Delayed Job. I never was interested in adding more unnecessary complexity to our dev and staging environments for a trade-off I didn't need (there wouldn't be a significant performance increase for my needs).

I've seen this pattern happen with a lot of Ruby projects: there's a popular Gem that people use that grows over time, then someone writes a blog post about why that package isn't suitable for their needs due to a design trade-off (often introducing a new Gem that is advertised as superior to the previous one) and then suddenly the old Gem stagnates, causing the maintainer to lose interest and updates stop pacing Rails versions. Sometimes the old Gem gets deprecated altogether and maintainers stick a big DO NOT USE sign at the top of the github README, all but guaranteeing there is no further community traction or organization for the project.

Meanwhile those of us using the old project chug along with a forked Gem that we cobble a bunch of patches into to meet our needs because there's no longer a centralized place to contribute to anymore. In some ways it's the double-edged sword of OSS. Maintainers aren't obligated to stay as maintainers of course, but it does get frustrating how quickly the community is willing to drop support of things that a lot people are using in production systems.

It definitely makes me reconsider the "don't reinvent the wheel" advice that is so adamantly thought of as a common sense convention in our craft.

mberning• 6 years ago

Sidekiq is one of the best pieces of software I have ever used.

bmn__• 6 years ago

Also see: https://news.ycombinator.com/item?id=9576864 Postgres Job Queues and Failure by MVCC

block_dagger• 6 years ago

Keeping your jobs in Redis (like Sidekiq does) seems to be a good feature to me. I’m curious how GoodJob compares when it comes to UI and queue management.

shay_ker• 6 years ago

I'm excited about ActiveJob because, finally, people will be able to build background jobs on things that aren't Redis. No hate on Redis - I'm a huge fan of it - but sometimes you have stronger consistency reqs that Redis does not have, and stronger availability reqs that SQS or PG don't have (aka multi-region jobs).

If the concurrency in ActiveJob become as good or better than Sidekiq, we can really get a lot of interesting stuff out there.

scruple• 6 years ago

I used Que [0] in a number of projects in the last few years that had stronger consistency demands. It can plug into ActiveJob. Those projects are still humming along without trouble today.

[0] https://github.com/que-rb/que

nthj• 6 years ago

Que also has a Golang port [1], which can be a tool to get towards The Citadel [2] for performance or dependency-heavy jobs without going full SOA

[1] https://github.com/bgentry/que-go

[2] https://m.signalvnoise.com/the-majestic-monolith-can-become-...

arcticfox• 6 years ago

As a fellow Que user, I'm happy to see this line in the README:

For example, GoodJob is currently ~600 lines of code, whereas Que is ~1,200 lines,

I've tried to dig into the Que internals before (looking into deadlocks) and they were gnarly; skimming through the GoodJob internals, it looks a lot more like what I'd hope for.

Exuma2• 6 years ago

Unfortunately its no longer maintained and his 2.0 branch is completely broken for me. I've been very stressed trying to find a que replacement, as almost all of my needs for job need ACID guarantees, and Sidekiq/Redis "best effort" is nowhere near what I need. I also refuse to pay $xxxx for Sidekiq pro just to get those guarantees.

Good job looks pretty awesome, I'll have to give it a shot at some point.

dorianmariefr• 6 years ago

i'm not sure why i should use this instead of delayed job for instance

pqdbr• 6 years ago

If you're using delayedjob, I strongly suggest you check out the Performance table in Sidekiq's readme. 465 seconds for DelayedJob against 14 seconds for Sidekiq for the same workload.

It's 7100 jobs/sec x 215 jobs/sec.

I wonder how GoodJob will compare.

https://github.com/mperham/sidekiq#performance

mbell• 6 years ago

That benchmark is just showing job overhead. That Sidekiq can do nothing 7100 times a second only matters when overhead is significant, i.e. when your jobs do almost nothing.

thibaut_barrere3• 6 years ago

delayed_job hasn't seen a release in 1 year, if that matters to you https://rubygems.org/gems/delayed_job/

joemclarke• 6 years ago

This is awesome, thanks for sharing! Sidekiq works well for me but it’s good to have an option that doesn’t require Redis.

jbverschoor• 6 years ago

Hm. Got falsely excited. No listen/notify etc? This really is just delayed_job

sideofbacon7• 6 years ago

GoodJob author here. I'm curious why you're specifically looking for listen/notify? I'm trying to prioritize that in the backlog.

juandazapata• 6 years ago

Hi, sorry to hijack this thread, but since you mentioned you're the author, I just wanted to ask you something. Do you have any plans to use a different locking mechanism other than the advisory lock? I'm asking because eventually every postgres-backed app that reaches a certain scale, requires a connection pooler (pgbouncer being the de-facto standard nowadays). We usually run pgbouncer in transaction mode, which doesn't support advisory locks. Any thoughts?

bdcravens• 6 years ago

In this post, I noticed comparison with other job libraries, but not Sidekiq, the most popular one. Why?

geoffharcourt• 6 years ago

I think they specifically wanted to compare themselves to queue systems that use the database as the storage for queued jobs.

sideofbacon7• 6 years ago

GoodJob author here. The reason is that I don't have any production experience with Sidekiq.

My target right now is someone, like myself, who would typically spin up a new project with delayed_job or que, and provide a better alternative with GoodJob.

Maybe in the future I'll do some more research on understanding why someone might switch from a Sidekiq/Redis to not-Redis.

mhoad3• 6 years ago

I feel like Rails is really starting to see some new life that has felt a bit absent from it for a while now. It almost seems like there is a new generation of people extremely burned out from the constant churn of the “JS-all-the-things” movement that just took over most of web development for the past several years.

There is a lot of exciting stuff landing in Rails and it’s surrounding ecosystems at the moment and I think it’s still probably the best choice for many new SAAS / web app based companies and startups.

WrtCdEvrydy3• 6 years ago

Rails was always great, JS just paid a lot more...

It felt great to get back into it having people pay to migrate their Rails apps to React and Node.

gav• 6 years ago

It's funny you say that, I've seen people pick a tech stack based on developer cost.

Maybe five years back I had a client in NYC who had a predominantly Java stack, but due to internal politics, wouldn't pay more than 135k for a senior developer when the market was wanting at least 25-30k more than that. Everyone they hired was pretty terrible.

At the time, Node developers were cheaper, so we split the application in two, wrapped all the old Java code with APIs, which was then able to be maintained by a small team while the front-end and any new features were all re-written with Node. It was architectural a better system--but the driving factor was really developer cost (the business hated to make any investments in technology).

The problem was that Node got popular and it got harder and harder to hire good Node developers at what the company wanted to pay. They had a big re-org and fired everyone I knew, so I don't know what they are doing now, but I often wonder if they just repeated the process with whatever up-and-coming language was more hip.

sanderjd2• 6 years ago

I've been out of this world for awhile so it's super interesting to see that JS was paying more than Rails. It was the opposite back in my day :)

rubber_duck2• 6 years ago

What's great about Rails ? Serious question from someone who landed into a mature Rails app and is now decidedly running away from that ecosystem after a year working in it.

Rails looks like an early take on MVC that was setup around fast project creation and encourages unmaintainable code - concerns are straight out retarded (a design pattern that encourages breaking encapsulation and makes dependencies impossible to trace) and fat models encourage coupling things that don't need to be coupled.

Then there's Ruby which in my opinion goes against Zen of Python which I'm a fan of - aliases all over the place for same thing, pointless name shortening and stuff to sacrifice readability, rails breaking conventions of standard library...

In the context of when it got popular I understand why it got the hype - replacing the PHP SQL in views garbage and Java 6 verbosity with XML configure everything, and the horrible ASP monstrosity.

These days I'd take Python as a more popular language, that I would say is better designed and has far better Windows support.

NPM/TypeScript and structural static typing is getting really good as well but is not as mature - but code sharing between client and server is a real thing.

Go emerged since the time of Rails hype.

.NET and JVM languages and frameworks got a lot better and scale far better with big code bases.

I don't really see where Rails is great compared to alternatives, it feels like legacy at this point. I'm not saying you can't write good maintainable apps in Rails either - I'm just saying other frameworks and languages will make it easier IMO.

techscruggs3• 6 years ago

What are some of the other exciting things happening in the Rails world these days?

czbond• 6 years ago

Thanks for asking - was curious the same. Always loved Rails, but then got into the "JS" toolset - which has been a cluster of extra required work.

mhoad3• 6 years ago

There’s a new release about to drop which is Rails 6.1 that covers some interesting developments.

GitHub took all of their code associated with running “web scale” applications that need to talk to multiple databases at the same time and put that into a dead simple native Rails framework.

Basecamp have spent the last couple of years (I think?) working in secret on what they claim is an entirely new way of doing all things front end. There isn’t a LOT of details on that at the moment and it’s kind of built up as a big surprise. But everyone who has had a behind the scenes look seems unusually excited.

There’s a kind of interesting web based interface for describing and developing all kinds of boilerplate parts of your application that could really speed up development time https://github.com/rails/rails/pull/35489

Some cool security stuff like this https://twitter.com/dhh/status/1268236728134889475?s=21 and promoting things like WebAuthn to be first class citizens.

But basically at this stage you have 3 major contributors of Shopify, Basecamp / Hey and Github extracting huge parts of their internal systems and rewriting them as mini Rails frameworks with famously simple APIs for people to use.

That’s obviously in addition to everyone / everything else. I think the future looks bright.

thibaut_barrere3• 6 years ago

Here are a few interesting pieces in Rails specifically:

- https://github.com/hopsoft/stimulus_reflex is inspired by Phoenix LiveView and is getting a bit of traction around me

- https://github.com/hopsoft/cable_ready is a companion project

- https://github.com/discourse/message_bus by Sam Saffron from Discourse is a nice way to implement live updates too, quite easily (video demo at https://twitter.com/thibaut_barrere/status/12565974431075860...)

- https://lamby.custominktech.com is a Rails + AWS Lambda integration which is also gaining a bit of traction

I also see interesting stuff in Ruby more generally these days:

- my own https://www.kiba-etl.org (data processing framework) is growing nicely

- https://sidekiq.org is very solid and used in most Rails app I've seen

- https://github.com/contribsys/faktory allows interop-jobs (e.g. create from Ruby, consume from something else), which is also interesting

- https://github.com/oracle/truffleruby is making very good progress

Just a few cherry-picked links, but I definitely think there are some nice evolutions going on in the Ruby world (speaking as someone also using Elixir in production!).

bbbobbb• 6 years ago

I am one of those "refugees", although not related to JS specifically. I think the last nudge way Hey releasing which made me consider RoR after all these years.

The motivation on my part is simple - I am getting really tired of microservices everywhere.

I understand why they might make sense in large organizations but the endless splitting of stuff that works (or could work if the energy was invested in fixing existing code) to the point where you have 3-5 services per developer is tiring.

Anyways, ranting aside, I have been learning Rails on the weekends and it's fun, even if there aren't that many job opportunities. If I later end up working in an ecosystem where the majestic monolith is something to aspire to, even better.

dwheeler3• 6 years ago

This looks very promising! I'm currently using active job, so I will need to take a look at this. Thanks for letting me know.

rubyn00bie2• 6 years ago

Despite my username, I haven't written any serious Ruby is like 5+ years; that is to say, I'm fairly removed from a lot of the changes in the Rails world.

Now, pardon me for my ignorance, but... isn't this just like Resque back in the day? Or like doesn't ActiveJob just support any ol' backend outta the box? What's the real use case for this? I'm genuinely curious not trying to be rude or diminish the work.

techscruggs3• 6 years ago

You can implement background processing with less operational complexity. This allows you to leverage activejob to get something up and running quickly and easily.

Granted, if you start having higher throughput, you want to move on from using postgres as your message bus.

why-el• 6 years ago

I didn't look into this one yet besides the home page, but I always thought Postgres would make a killer backend for ActiveJob, leveraging advisory locks for synchronizing jobs and such. Resque is Redis backed, but if you don't want to add that as a dependency and already have Postgres setup, then this would be a great fit.

paulryanrogers2• 6 years ago

Because of the MVCC implementation (needing VACUUM) it's not ideal without tuning.

thibaut_barrere3• 6 years ago

I believe Resque was fork based (at least initially, it may have changed, I haven't looked at it in a while!), while GoodJob appears to be multithreaded (like Sidekiq), so this is quite different in terms of performance & throughput.

sideofbacon7• 6 years ago

GoodJob author here.

The core reason I wrote it was to see how lean/simple I could write a database-backed ActiveJob adapter today. And hope

In practice any adapter should _just work_, but also all the other adapters pre-date ActiveJob (Rails 4.2) and Concurrent::Ruby (adopted in Rails 5.0 I think). The assumption is that building GoodJob on top of what already exists in Rails today, it can be performant (enough) and simple (easy to understand, maintain, keep compatible with new versions of Rails, etc). That's not a big claim, but maybe it's compelling.

rubyn00bie2• 6 years ago

Awesome! Thank you so much for the reasoning behind it. I haven't had a chance to look at Concurrent::Ruby but that _sounds_ like a pretty good reason all by itself!

As a big plus for a lot of folks who don't need absurd throughput, this makes for one less dependency by using the same db you already have. I'd be sold given the right use-case, thanks for sharing this, mate and _good job!_ ;)

techscruggs3• 6 years ago

This looks great. I'd love to remove Redis from my tech stack on applications with low throughput background jobs. Sadly, it doesn't appear to have a UI.

Resque and Sidekiq are both good enough solutions, but what makes them my defacto choice is the robust web UIs that comes with them.

samokhvalov• 6 years ago

To make it scale well, two things are required:

1. TRUNCATE if cleanup is needed (no DELETEs) + partitioning.

2. SELECT .. FOR UPDATE SKIP LOCKED or advisory locks.

It's worth learning from Skype's PgQ developed in 2000-s.

Update: found the work with advisory locks in the code, great.

SkyLinx• 6 years ago

Would this work with pgbouncer? I'm wondering because of the advisory locks.

sideofbacon7• 6 years ago

GoodJob author here. Excellent observation.

It should work if PgBouncer is using session-level pooling, but not transaction-level pooling. I made a ticket to document this: https://github.com/bensheldon/good_job/issues/52

I don't have much experience with PgBouncer. What's the scale/need when a team would use PgBouncer? That would help me prioritize supporting it better.

Exuma2• 6 years ago

The main reason I can think of would be when you have hundreds of workers accessing a DB but the DB only has a small connection limit, say 200 or something. You can have the workers access the connection through pgBouncer to bring that up into the thousands.

cpursley• 6 years ago

For a very nice library in the Elixir/Phoenix ecosystem have a look at https://github.com/sorentwo/oban

regulation_d• 6 years ago

I think one of my biggest annoyances, from a development perspective, with Sidekiq is that it typically moves you in the direction of running foreman or something like that, which makes using the pry a pain.

One thing I really like about Phoenix development is that I don't have to change my flow to use a REPL while still being able to run background jobs.

Jack_uio• 6 years ago

I was just assigned to a project based on zend 2.x php framework (2015 version) and angularjs(version1) (not angular.io). Just looking at the code, I just want to scream, because I was told to make changes and add features. I could re-implement everything in Rails in about a week's time but manager's opinions just drown me.

BilalBudhani• 6 years ago

This looks like a great library on the surface. I would very much like to have a simpler alternative to Sidekiq for projects which doesn't require that level of complexity. Also, not having to add Redis just to run background processing makes life so much easier. I would like to thank the author of the library for all their efforts.

GoodJob – a Postgres-based ActiveJob back end for Ruby on Rails

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