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Cache Busting a React App

Dinesh Pandiyan on April 14, 2019

TL;DR - SemVer your app and generate a meta.json file on each build that won't be cached by the browser. Invalidate cache and hard reload the app w... [Read Full]
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I think it should be noted the window.location.reload(true) will only disable the cache for the current page. Any subsequent requests (async js/css, other pages, images, etc.) will not be cache busted. It's also very dependant on the browser. Chrome for example hangs on to cache for dear life unless instructed by headers to do otherwise. The best way to ensure cache is busted is to fingerprint filenames based on the files content and to never cache pages (e.g. index) so references remain fresh.

 

James — That's very true. Browsers sometime decide to ignore window.location.reload(true).

But caches.delete() will always delete the cache. So reloading synchronously after cache.delete() should clear the cache for the user.

 

You mention reloading synchronously... I was having issues with infinite looping when our app updated and it seems due to window.location.reload firing before our caches had time to clear, in the code you shared for CacheBuster. Simply adding aPromise.all() on the caches.delete() promises solved the issue in our case.

Thank you for taking the time to share this!

Hi Matt,

We are facing the same issue, can you please let me know the exact code you have used to solve this issue?

Something like this? Please correct me if I am wrong.

caches.keys().then(async function(names) {
await Promise.all(names.map(name => caches.delete(name)));
});

Yep, I used promises but that's pretty much exactly what I did, then do the window.location.reload after your await

Thanks, I got it now.

Hi a-ssassi-n,
I'm having the same issue and I tried to do it the same way as this:
refreshCacheAndReload: () => {
if (caches) {
caches.keys().then(async function(names) {
await Promise.all(names.map(name => caches.delete(name)))
})
}
window.location.reload(true)
},
And it keeps happening did I miss something?, can you please give me any guide?

if (caches) {
  const names = await caches.keys();
  await Promise.all(names.map(name => caches.delete(name)));
}
window.location.reload();
 

Hi Dinesh, good article.

I was wondering though, why would you need a cache-invalidation mechanism. We are developing with angular, but I believe, you can setup things in the same way with React.

We have also been struggling with browser caching, because SEO loves resources cached for as long as possible. So here is our current setup:

  • js and css files all have a hash part in their filename, so we cache them forever (366 days to be precise), but if they change, the filename changes, so no trouble there.
  • index.html - never cache it. Here we have references to js and css files.
  • fonts, images - we cache them forever (366 days again), but we version them all. Therefore, when we update them, we just bump up the version and cache invalidation solved.

This way, SEO performance score is happy that we cache everything forever, but also, we never have to deal with invalid data.

I am not trying to sell my approach here, I am just honestly curious what is your use case for such cache invalidation mechanism? Thanks.

 

Hey Eddy — Good question.

We definitely need to leverage browser and server cache (PWA service worker implementation for cache control is a lot better).

But there are still a few gotchas we haven't solved yet. These "recommended" ways work most of the time but in some rare cases, they won't as I highlighted at the beginning of the post.

So this technique is more of taking control of cache "within your app code" and use this as a fallback approach when all else fails.

We have a peculiar case where I work — safari web app pinned to the home screen and users won't quit it for a few months (restaurant iPads). We simulated native app behavior with PWAs but cache busting instantly after a new deploy was tricky. This technique eventually helped us.

 

The service worker that comes with react does cause scenarios where the cache is not busted that feel a bit weird. For that reason it was removed from create-react-app a while ago, as discussed here github.com/facebook/create-react-a...

The mechanism @eddyp23 mentions works perfectly and it's supported by default by create-react-app create-react-app.dev/docs/producti...

 

This is a really great solution and very well explained in this article! There's just one problem: location.reload(true) is deprecated! Calling location.reload() is still in the spec, but passing true to force the browser to get the page again and bypass the cache is deprecated. And because it's deprecated, some browsers are starting to ignore it. As a result, we are seeing an infinite loop where our browser keeps reloading the same page from cache. Have you thought about an alternative that will achieve the same result?

 

Hi Dinesh, thanks for the great article. I found it very helpful and I use it for a project my team is working on. At a point, you say: "It won't be cached by the browser as browsers don't cache XHR requests." Well, for some reason my browser is catching it.
I will try
fetch(/meta.json?${new Date().getTime()}, { cache: 'no-cache' })
as @ppbraam suggested dev.to/ppbraam/comment/gdac
If you have any other idea that may help I would appreciate it. Thanks in advance.

 

Hi Dinesh,

Good work.

I am having an issue when the metal.json version not match package.json version it goes to infinit loop because the meta.json is not updated.

Any suggestion ?

Thanks

Nic

 

If you could create a sample repo that reproduces the problem I can take a look and see what's happening.

 

OK I will try.

I also got this error when i manually refresh the page after new version has been updated in server :

service-worker.js:1 Couldn't serve response for http Error: The cached response that was expected is missing.

 

This is stellar. Looking forward to giving this a shot. Thank you Dinesh!

 

I am new to caching and as per this article, this solution of deleting a stale cache can be achieved without a refresh? My understanding is EVEN with a refresh, some applications are cached, hence various solutions used to invalidate cache.

In my react app, if I refresh my app, the latest code is reflected. It's only IF the code is not refreshed and I go to another page, nothing is updated.

I am also using react router. Does an internal request need to be made for meta.json then?

 

I am facing issues implementing it. My application went into an infinite reloading state. Though I tried using Promise.all as suggested by @a-ssassi-n but it didn't work for. Can anybody help me with this?

 

Thank you for this solution!

If for some reason your cache still won't clear, maybe this will help:

fetch(`/meta.json?${new Date().getTime()}`, { cache: 'no-cache' })

 

I have same problem with rca, it don't work well. I always have same meta.jon version, is it normal?

 

Hi Dinesh,
In my case the fetch('/meta.json') does not work. How it will tyake the meta json from public folder.

 

Hi, are you able to figure out meta.json file, I am also facing the same issue ::

Failed to load resource: the server responded with a status of 404 (Not Found)

Cannot GET /meta.json

 

Nice one Dinesh, thanks for taking the time to prepare this.

 

Awesome work Dinesh, this really helped our project fix the caching issues we were having!

 

Hi Dinesh, My app is not being created using create-react-app, so Service Worker is missing there, so this approach may not work, but then I am not sure how can I clear the browser cache programmatically for user to see the updates, happy to share more information if any one willing to help, thanks in advance.

 

Amazing article. Worked like a charm.

caches.keys().then(async function(names) {
await Promise.all(names.map(name => caches.delete(name)));
});

This helped in the extension of the entire article. Thanks a lot, Dinesh.

 

How does this compare to using service workers for offline caching?

 

Leveraging Service workers for controlling your cache should be the de-facto first approach. Service workers are pretty great and hashing every new build is a life saver. But there are situations where we will need custom cache control within the code. This approach will help in such situations.

More info in this comment — dev.to/flexdinesh/comment/a79c

 

Just what I was looking for! Thanks Dinesh! 😁

 

Hey Dinesh

Thanks for this article, really helpful and clear, worked like a charm and easily slotted into the build process!

 

Hello Dinesh, amazing article.

 

Hi,
i am facing an issue on production. Unable to access /meta.json endpoint..working fine on local.
getting this error: SyntaxError: Unexpected token < in JSON at position
Regards
Abdullah Saud

 

I had the same issue, this change helped me

fetch('/meta.json',{
headers : {
'Content-Type': 'application/json',
'Accept': 'application/json'
}
})

 

@abdullah727 Did you ever manage to get the "Unexpected token

 

Dinesh, how do you handle the meta.json during development, with hotloading?

 

Remember to push your commit with --tag attribute — git push origin master --tags
what does this line means and why it is important?

 

I was wondering the same thing. Is it supposed to change anything?

 

it keeps rerendering

 

Remember to push your commit with --tag attribute — git push origin master --tags
what does this line means and why it is important

 

Its because with each version update the code will be tagged and you need to have these tags in the remote too, otherwise you might end up creating duplicate version

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