I love how Django just keeps slowly improving at every release. 6.0 is especially cool, including lots of really useful new features. Who said dependable tech was dull - this is the way is should be done. Well done all who contribute.
Any code or blog written by Adam is worth spending some time on.
It will be interesting to see how the tasks framework develops and expands. I am sad to see the great Django-Q2 lumped in with the awful Celery though.
Celery is the worst background task framework, except for all the others.
There are bugs and issues, but because so many people are using it, you’re rarely the first to stumble upon a problem. We processed double-digit millions of messages daily with Celery + RabbitMQ without major obstacles. Regardless of what people say, it should be your first go-to.
It's okay till it's not. Everyone I know who had Celery in production was looking for a substitution (custom or third-party) on a regular basis. Too many moving pieces and nuances (config × logic × backend), too many unresolved problems deep in its core (we've seen some ghosts you can't debug), too much of a codebase to understand or hack. At some point we were able to stabilize it (a bunch of magic tricks and patches) and froze every related piece; it worked well under pressure (thanks, RabbitMQ).
Because it’s a seducer. It does what you need to do and you two are happy together. So you shower more tasks on Celery and it becomes cold and non-responsive at random times.
And debugging is a pain in the ass. Most places I’ve been that have it, I’ve tried to sell them on adding Flower to give better insight and everyone thinks that’s a very good idea but there isn’t time because we need to debug these inscrutable Celery issues.
Celery is great and awful at the same time. In particular, because it is many Python folks' first introduction to distributed task processing and all the things that can go wrong with it. Not to mention, debugging can be a nightmare. Some examples:
- your function arguments aren't serializable
- your side effects (e.g. database writes) aren't idempotent
- discovering what backpressure is and that you need it
- losing queued tasks during deployment / non-compatible code changes
There's also some stuff particular to celery's runtime model that makes it incredibly prone to memory leaks and other fun stuff.
> your side effects (e.g. database writes) aren't idempotent
What does idempotent mean in this context, or did you mean atomic/rollback on error?
I'm confused because how could a database write be idempotent in Django? Maybe if it introduced a version on each entity and used that for crdt on writes? But that'd be a significant performance impact, as it couldn't just be a single write anymore, instead they'd have to do it via multiple round trips
In my experience async job idempotency is implemented as upserts. Insert all job outputs on the first run. Do (mostly) nothing on subsequent runs. Maybe increment a counter or timestamp.
I tried django-q and I thought it was pretty terrible. The worst was that I couldn't get it to stop retrying stuff that was broken. Sometimes you ship code that does something unexpected, and being able to stop something fast is critical imo.
Fundamentally I think the entire idea behind celery and django-q is mostly misguided. People normally actually need a good scheduler and a bring-your-own queue in tables that you poll. I wrote Urd to cover my use cases and it's been rock solid.
I'm of the opinion that django task apps should only support a single backend. For example, django-rq for redis only. There's too many differences in backends to make a good app that can handle multiple. That said, I've only used celery in production before, and I'm willing to change my mind.
Template partials look good, which is one of the key reasons frameworks like React are as good and popular as they are, because you can reuse small segments of code.
I do a check for `request.htmx` in my views and conditionally return a template partial as needed. This reduced my need for one-off view functions that were only returning partials for htmx. Works pretty well from my experience.
Partialdef inline is the real win. Lets you define parts of a page without needing to place them in another file. Reduces the mental overhead of imagining how the inclusion will look because it’s already there.
The use case is mainly driven by htmx where you will have lots of these partials and the view code renders them as individual responses.
It's just syntactic sugar, making life a bit easier for HTMX users (cf. "htmx was the main motivation for this feature").
I'm using Unpoly and I just render the whole page and let Unpoly swap the content according to the target selectors, so no need for this. Not much difference in perf if you dont generate gigantic pages with heavy header/footer.
Yeah, but I was doing the same thing 10 years ago with include mixed with extends and blocks. I can just include a file inside a template or render it directly.
you're kinda right, {% partial ... %} vs {% include ... %} is not a big difference, but my mind was vaguely thinking that "includes" have often been seen as large templates, whereas partial have been after the component era with the idea of making small blocks. (my 2 cents)
Dude, I used Django at 1.x - before they even had an ORM. The fact that it is adding a way to run tasks, almost a quarter of a century later, is wild to me.
I am not roasting it or anything, go Django, but just an observation.
Correct. Django 6.0 comes with a standardised API, with 2 testing backends (ImmediateBackend and DummyBackend). You need a third-party backend to store and execute tasks.
Given that Python tends to produce fewer hallucinations when generated by LLMs I wonder if former Django developers using AI tools are secretly having a blast right now.
Whenever I saw people complain about LLMs writing code, I never really understood why they were so adamant that it just didn’t work at all for them.
The moment I did try to use LLMs outside of Django, it became clear that some frameworks are just much easier to work with LLMs than others. I immediately understood their frustrations.
I think another ace up Django's sleeve is that it has had a remarkable stable API for a long time with very few breaking changes, so almost all blogposts about Django that the LLM has gobbled up will still be mostly correct whether they are a year or a decade old.
I get remarkably good and correct LLM output for Django projects compared to what I get in project with more fast moving and frequently API breaking frameworks.
After the move away from the use of 'master' in programming parlance (understandably IMHO), as a Brit I'm always slightly surprised to see 'nonce' still being acceptable.
It makes me sad when a secondary meaning, which does not even overcome the main meaning in usage, becomes an obstacle for the normal use of a word. It's like seeing a rainbow as a sexualized symbol not fit for children, because it also happens to be used by LGBTQ+ community. (BTW, since you're a Brit: did people stop using the word "fag" to refer to a cigarette?)
I mean, it is sad. But unfortunately that is what happened with "master", "slave", "whitelist", and "blacklist". No reasonable person construed these as offensive or having any implications about the wider world. But there are people in our profession who are determined to take offense where none is given, and unfortunately they got their way.
Well, "slave" has a pretty direct main meaning of an oppressed person doing forced labor. The word "master" is much milder in this regard (compare "master's degree" and "slave's degree"). The word "nonce" in normal usage seems even more removed from any pejorative secondary meanings.
That didn't stop people from throwing a fit over master-slave terminology in software (having nothing to do with slavery), going so far as to rename long-standing development branch names, as well as put significant effort into removing such terms from the code itself and any documentation.
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