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0 pointssimonw14y ago0 comments

I disagree on one point there... if you're building both an API and a website, there's no reason at all to use both Flask and Django. I can't imagine that the benefits would outweigh the disadvantages of having to deal with two frameworks instead of one.

I'd also argue in favour of ditching Django's auth. It's fine if your project has very simple auth requirements, but these days very few interesting projects have simple auth requirements - plus it's much easier to extend the functionality of your own Account models than to try and hook extra stuff on to Django's.

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buro914y ago· 2 in thread

> I can't imagine that the benefits would outweigh the disadvantages of having to deal with two frameworks instead of one.

Separation of concerns, loose coupling.

I tended to find (in the few Django projects I worked on), that models were frequently accessed outside the app that created and owned the model. The subsequent dependency diagram would be spaghetti.

We had apps for each significant feature area, and when we wanted to drop a feature it was my desire to just remove an app.

It may well have been our implementation that was the problem (poorly separated concerns across apps), but we made great strides at solving these problems by using APIs to both force the de-coupling and to increase our confidence that our mobile clients (using the API) had the same capabilities available to them as the website (because no Django dev could cheat and make a call without the API existing).

Why Flask and not just Django again? That came down to personal preference over how clean it is to handle headers correctly (Accept headers, CORS and other things were fun), layout of the code and project, simplicity of testing, etc.

Mostly it was just subjective and personal preference, once we saw that the Django projects we had tended not to follow loose coupling, we used APIs as a way to increase our own discipline. Preferring that the architecture helped ensure the way we wanted to work on (and maintain) the code.

Auth we had already externalised (into the edge of the network, implemented within Varnish, similar to Flickr's GodAuth).

clarkevans14y ago

How do you handle "foreign key references" between modules in your new approach (using APIs to decouple?).

buro914y ago

That's one of the fun issues with service oriented architecture.

You either choose high-chatter and low complexity, or low-chatter and high complexity. As high-chatter is also a decrease in performance (mostly due to JSON serialisation/deserialisation and HTTP requests), we opted for low-chatter.

Resources that were a composite of other resources had their own knowledge of how they were composed, and generated their own IDs to save that knowledge. Each new composition resource got it's own Accept header identifier as a result.

Within that composition resource, there wasn't just knowledge of "I'm composed of x:17 and y:3", but also knowledge of how to search across the underlying services. This could be to call search on the underlying service if one side of the composition was dominant in applying the filter to the dataset.

Where it was trivial, a search index belonging to the composed service was used. And because this duplicates data from the underlying resources, messaging was put into the underlying service to notify the composed service of changes that affect searches.

For simplicity you can just imagine that we had some kind of table in the composed service, with ID on each row that because the ID of the composed resource, and that we could search that table, and that messaging magic kept that table in sync.

We could do all of this because we owned all of the services. If we didn't, then I imagine we would have followed a similar path to http://ql.io/

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