Faro keeps reporting cacheHitStatus=fullLoad

[fhalde]

We're using the ky library to handle API requests. Our setup relies on HTTP caching with ETag-based validation, where the server returns a 304 Not Modified to confirm cached content is still valid.

Since ky is built on top of the Fetch API, the faro.performance.resource events should, in theory, capture this correctly. However, we consistently see Faro reporting cacheHitStatus=fullLoad, even when the API responds with 304 Not Modified.

Any ideas on what might be causing this or what I should investigate further?

[codecapitano]

Thanks for the report @fhalde

• Is this happening for all browsers?
• If you look at the respective resource entries what are the values for:
  • transferSize
  • decodedBodySize
  • encodedBodySize
  • responseStatus

[fhalde]

Hi @codecapitano
I only tried this with Chrome

chrome
encodedBodySize=0
decodedBodySize=0
transferSize=0
responseStatus=200

on network tab

not sure why the response status was reported as 200 in the event

[fhalde]

just tried it on firefox and i got back cacheHitStatus=cache but response is still responseStatus=200

firefox
encodedBodySize=1954
decodedBodySize=1954
transferSize=0
responseStatus=200

[codecapitano]

Hmm responseStatus is directly taken from the browsers performance entry.

You can paste the following snippet to your browser console and double check the response data.
This directly hooks into the browsers perfoemance timeline API.
What status code do you see there?

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    if (entry.entryType === 'resource') {
      console.log(`URL: ${entry.name}`);
      console.log(`Respons Status: ${entry.responseStatus}`)
    }
  });
});

observer.observe({ type: 'resource', buffered: true });

[fhalde]

your script reported it as 'Respons Status: 200' even though the network tab had 304 , both on Chrome and Firefox

since the endpoint i'm hitting is cross origin, there is a OPTION (200) followed by GET (304) btw. Not sure if it is relevant

[fhalde]

faro sdk 1.19.0

[codecapitano]

your script reported it as 'Respons Status: 200' even though the network tab had 304 , both on Chrome and Firefox

This the vanilla response from the browsers performance timeline-api, no Faro involved at all.
So we don't have a Faro issue here.

So getting a 200 in your case might be caused by different things like:

• You have intermediate redirects and final response is 200
• Resource is served from cache (transferSize 0) and browser adds a 200 bc the retrieval from cache is successful