WebDAV client returns 0 for the size of files as well as directories about chromeos-filesystems

[lavelle]

Wondering how to handle this. The S3 metadata response doesn't provide the file size either, so instead I download the whole file and check its length. This is very inefficient for big files! Inefficient and incorrect are both bad, but we should at least pick one so its consistent across providers. Which one should we use?

Another option is to return -1 or another invalid value as an error code for backends that don't support efficient retrieval of the size, and only have a valid value present for backends that do provide the size efficiently as a number in the metadata response. I'm inclined to go with this.

Thoughts @jmuk @mtomasz-chromium?

[lavelle]

Or the provider could have a method like hasCorrectSize that the FSP API can call to check if it will be returning a valid size, and use this to determine whether to show the size in the browser.

[mtomasz-chromium]

The current file system implementation requires a file size, and bad things may happen if we don't provide it.

Can we get the file size from the Content-Length field using a HEAD HTTP request? That's still inefficient, but at least we wouldn't need to download the entire file. Would it work?

[mtomasz-chromium]

According to http://docs.aws.amazon.com/AmazonS3/latest/API/RESTBucketGET.html, AWS S3 does provide the size.

[lavelle]

That would probably work for WebDAV (although might depend on the server implementation). It might be in the AWS raw REST API but I don't think it's in the JS library - the response of headObject doesn't return a size, and that uses HTTP HEAD.

Even if we can get it working for the current two, we should still plan for the eventuality of a provider coming along whose API does not provide an efficient way to get the size of a file, and a way for them to handle it.

[mtomasz-chromium]

I'm not sure if I understand. The AWS API returns the size according to the link you provided:
"ContentLength — (Integer) Size of the body in bytes."

[mtomasz-chromium]

As for WebDAV, did you consider specifying the "getcontentlength" field in the request? http://msdn.microsoft.com/en-us/library/ms879496(v=exchg.65).aspx

[lavelle]

Huh okay I totally skipped over that property. I guess I was just looking for something called size. I will try working with custom requests for WebDAV. Currently it just fetches the default response (sends no data in the request) but I guess it won't be too hard to customise.

[lavelle]

WebDAV is fixed in #42 and S3 is fixed in #52. Closing.