[Translation] Make http requests synchronous when reading the Loco API

[Kocal]

Q	A
Branch?	5.3
Bug fix?	yes
New feature?	no
Deprecations?	no
Tickets	Fix #...
License	MIT
Doc PR	symfony/symfony-docs#...

Hi!

Since we migrated from the PHP Translation's Loco Adapter to the Symfony's Loco Translation Provider, we started to have 429 errors from the Loco API when running our CI or deploying our code on review apps/staging/production environments:

Some screenshots

We have asked to the Loco support and this is their response:

Hello.

You will never get a 429 if you make single threaded requests. i.e. waiting for a response before dispatching another requests. As noted in the API usage limits: parallel requests burst the response speed limit. This is currently the only thing that would invoke a 429. I can provide more detail on the implementation if you would like.

This measure is in lieu of quota based rate limiting which will one day be added, but currently no other limits are in place in terms of number of requests.

Which makes sense. AFAIK, the PHP Translation's Loco Adapter makes synchronous requests to get translations from Loco.

Some Blackfire traces, it does not impact performances:

• before: https://blackfire.io/profiles/315f0748-76f8-4817-b59d-54ea482e1558/graph
• after: https://blackfire.io/profiles/a6779b3e-b2ae-4870-b67f-667fe2016c0b/graph
• delta: https://blackfire.io/profiles/compare/406d1f86-d9d8-45f1-9f8b-5c371d0973a3/graph

I consider this PR as a bug-fix and not a feature, that's why I've targeted 5.3.

WDYT?

ping @welcoMattic

[Kocal]

Checks failures are unrelated I think.

[welcoMattic]

It is legitimate, as you profiled it and there is no big difference I'm ok to merge it. Thank you @Kocal

[nicolas-grekas]

BTW, is anyone in touch with Loco, because so far they didn't answer to our ping to back the bridge.

(Crowdin and Lokalise did, so you know which bridge you'd better use ;) )

[Kocal]

The two foreach have been merged!

[stof]

I suggest adding a comment in the code mentioning that the Loco API forbids concurrent requests, to explain why this provider does not take advantage of the request concurrency allowed by http-client (so that it does not get refactored in the opposite way by someone not knowing about this API limitation).

[Kern046]

BTW, is anyone in touch with Loco, because so far they didn't answer to our ping to back the bridge.

They answered us quite quickly about this issue, I contacted them via their contact form 🤷

[Kocal]

A comment has been added, thanks for your reviews.

[fabpot]

Thank you @Kocal.