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zalando / tailor

A streaming layout service for front-end microservices
http://www.mosaic9.org
MIT License
1.73k stars 140 forks source link

Obligatory fragments #251

Open shilangyu opened 6 years ago

shilangyu commented 6 years ago

Currently only a primary attribute makes a <fragment /> obligatory (if fails to load, creates an error). But it means we are limited to 1 obligatory <fragment /> per page.

reason

Sometimes there are pages that need more than one microfrontend to work properly, therefore if any fails i'd like Tailor to create an error just like with not working primary fragment.

proposition

maybe an obligatory attribute (shouldnt be a breaking change)

<fragment obligatory src="cart.microfrontends.io"></fragment>
<fragment obligatory src="products.microfrontends.io"></fragment>

if any of the two fails -> produce error

vigneshshanmugam commented 6 years ago

The reason primary fragment exists in the first place is for the SEO (to generate a valid status code of the page) and not send 200/500 all the time to the client.

I am not sure how will you deal with status codes when two fragments have influence on the page, do you still mean to keep primary and introduce the obligatory attribute?

The way we deal with this problem is to have a fallback-src attribute for the fragment, which can still render a usable page with most of the functionality.

shilangyu commented 6 years ago

do you still mean to keep primary and introduce the obligatory attribute?

Yes.

The way we deal with this problem is to have a fallback-src attribute for the fragment, which can still render a usable page with most of the functionality.

Let's say the fallback-src also fails. Tailor currently will ignore it, thats where obligatory comes in, makes sure to raise an error so that we can act accordingly.

vigneshshanmugam commented 5 years ago

@shilangyu yeah got it, raise an error in the sense of returning 500 page?

shilangyu commented 5 years ago

500 sounds good, would the tailor.on('error', () => {}) be called after such error?

vigneshshanmugam commented 5 years ago

After having some thought process, I started to feel like this would mean we have to hold on to the response stream till all the obligatory fragments respond (normal src and also fallback-src) which will have a huge performance impact on time to first byte time.