01 Oct 2010 18:03

It's not a secret Wikidot uses Lighttpd web server to serve its service. We also use X-Sendfile mechanism to deliver files more intelligently.

Instead of having a PHP process copying file through FastCGI to Lighttpd (which would copy it again to the client) we send a special header to Lighttpd naming the file it should serve to the client. This means PHP processes are terminated quicker, which result in overall better performance.

When working on a Wikidot bug (some uploaded files with some special characters in their names are not accessible using links generated by Wikidot itself), I discovered Wikidot also doesn't serve files whose name end with a space.

The problem disappeared when I (just for test) disabled X-Sendfile mechanism. Pure PHP has no problems in reading such files and sending them through Lighttpd to browser, so it seemed there's a problem with Lighttpd.

Lighttpd v1.4.24 introduced a second X-Sendfile header: X-Sendfile2, which asks Lighttpd to send a chunk of a file (from byte X^th, to Y^th), but also a whole file (from byte 0^th to the last one). The syntax is:

X-Sendfile2: PATH RANGE

Where PATH is URL-encoded file path (PHP's rawurlencode, not the non-standard urlencode), RANGE is X-Y (or "0-" for whole file), so changing:

header("X-Sendfile: " . $path);

to

header("X-Sendfile2: " . rawurlencode($path) . " 0-");

fixes the problem.

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