Cloudflare Developers•4mo ago

`fetch(this.url, { method: 'HEAD' });` returns -1 for `content-length`

I have a file on cloudflare pages with a size of a bit more than 5.5MB. I normally retrieve the file in chunks, but to do so, I need to know the file size. The normal way to obtain the file size is is to do a fetch(this.url, { method: 'HEAD' }); and then retrieve the property content-length. Unfortunately this returns -1. Here's the kicker, if I open another tab and enter the URL to the file to download it, the next time I try repeat the fetch, the content-length is correct. If anyone know what's going on, my page is at https://mnm-guide.pages.dev/free The data file is https://mnm-guide.pages.dev/madeira.pmtiles Loading the page will fail to load the map, but if you download the file first, it will succeed. Any way to fix this problem?

4 Replies

Erisa•4mo ago

and then retrieve the property content-length.

whats the code you use to do this?

funmiles.OP•4mo ago

Here are the lines:

const reply = await fetch(this.url, { method: 'HEAD' });
console.log('Fetch got a header info for', this.url, 'of', reply);
const clString = reply.headers.get('content-length') || '-1';
size = Number.parseInt(clString);
console.log('Length is', size, 'from', clString);

const reply = await fetch(this.url, { method: 'HEAD' });
console.log('Fetch got a header info for', this.url, 'of', reply);
const clString = reply.headers.get('content-length') || '-1';
size = Number.parseInt(clString);
console.log('Length is', size, 'from', clString);

You can see the log prints @Erisa It works from the development server but not once deployed. The file is there and readable, since it can be downloaded and once downloaded, reloading the page reruns the above code and it works. So it feels as if maybe the file is compressed on cloudflare and they do not give the size, but once it's been downloaded, it caches the size?

Erisa•4mo ago

const clString = reply.headers.get('content-length') || '-1';

this sounds like cloudflare isnt the one returning -1, but rather cloudflare isnt giving any header and you are just defaulting to -1? cache would make sense - if there wasnt a length from the upstream but then it was put into cache and now it has a length

funmiles.OP•4mo ago

@Erisa I saw that after pasting. So it does not return a size at all. Which is still not the desired result. What other way is there to obtain the size of a file without downloading it? Stranger behavior still: If I try to fetch a range of the file for the first 1MB, fetch succeeds but the ArrayBuffer has the length of the whole file. Asking for a range starting from 1MB down gives the same thing. It looks like until a download is initiated, the headers are totally ignored.

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`fetch(this.url, { method: 'HEAD' });` returns -1 for `content-length`