Hi,

first of all, a shout out to all ZuriHac2014 folks, thanks for the gentle introduction to the deeper trenches of Haskell infrastructure!

I spent a bit of time looking into why "cabal update" always redownloads the entire package list even though the code has explicit support for etags, and it looks like etags are broken on the server side. The server does serve "Etag" headers, but does not react to If-None-Match:

$ curl -I --header 'If-None-Match: "1ea6c9a3168b9c186d5bbafd065ce5ec"' hackage.haskell.org/packages/index.tar.gz

HTTP/1.1 200 OK

Server: nginx/1.6.0

Date: Mon, 09 Jun 2014 23:22:49 GMT

Content-Type: application/x-gzip

Content-Length: 7193838

Connection: keep-alive

Content-MD5: 1ea6c9a3168b9c186d5bbafd065ce5ec

ETag: "1ea6c9a3168b9c186d5bbafd065ce5ec"

Last-modified: Mon, 09 Jun 2014 23:10:44 GMT

In this case the server is supposed to return a 304 code because the ETag matches, but it returns the usual 200.

Here's a well-behaved server for comparison:

$ curl -I --header 'If-None-Match: f89ef04efbcb1bbd413c9170523beeb1' http://upload.wikimedia.org/

HTTP/1.1 304 Not Modified

Last-Modified: Thu, 03 Oct 2013 22:29:34 GMT

Etag: f89ef04efbcb1bbd413c9170523beeb1

X-Timestamp: 1380839374.33426

X-Object-Meta-Mtime: 1366745378.0

Content-Type: text/html

X-Varnish: 2552484147 2541352860, 2937266545 2853346814, 523731362

Via: 1.1 varnish, 1.1 varnish, 1.1 varnish

Accept-Ranges: bytes

Date: Mon, 09 Jun 2014 23:29:36 GMT

Age: 38954

Connection: keep-alive

X-Cache: cp1064 hit (336), cp3010 hit (1791), cp3007 frontend miss (0)

Access-Control-Allow-Origin: *

Access-Control-Expose-Headers: Age, Content-Length, Date, X-Cache, X-Varnish

Note the 304 return code.

I do not know about the configuration in use on the server, but something seems to be wrong there. There are some nginx bug reports [1] about similar issues, not sure if they are relevant here.

[1] https://github.com/rgrove/rawgit/issues/13

Best regards,

--
Gintautas Miliauskas

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