Lighttpd

This feature is important if you have a load-balanced farm of lighttpd servers, serving the same files, on each request from each server, the Etags are different using the same file.

I have used stable web servers packages from your PPA. Tested this on Ubuntu 9.10 and 8.04.

I get this on dmesg: lighttpd¹³⁶³⁵: segfault at 00000000 eip 08063bd2 esp bfb7b080 error 4

Also, i have all etags disabled and enable compress is when it getss broken, disabling compress.* options it does not segfault's.

compress.cache-dir = "/var/cache/lighttpd/compress/"
compress.filetype = ("text/plain", "text/html", "application/x-javascript", "application/javascript", "text/css", "text/xml", "application/xhtml+xml")
compress.max-filesize = 5120

Now i understand. But some file get generated locally on each machine for faster local reading, so mtimes will not be the same on every machine, reading mod_compress.c, i don't understand why it has to use ETag and Last-Modified if it's configured to not use it ?, I use mod_expire to configure the expire time. Also Last-Modified should be allowed to be disabled.

Also the failure is related due to an integer underflow:

(gdb) p
$4 = {ptr = 0x0, used = 0, size = 0}
(gdb) bt
#0  0x08063ce0 in etag_mutate (mut=0x80c6678, etag=0x812d0d0) at etag.c:43
#1  0x00705d28 in ?? () from /usr/lib/lighttpd/mod_compress.so
#2  0x080632f8 in plugins_call_handle_subrequest_start (srv=0x6, con=0x80c6330) at plugin.c:265
#3  0x08050b56 in http_response_prepare (srv=0x8074008, con=0x80c6330) at response.c:722
#4  0x08054572 in connection_state_machine (srv=0x8074008, con=0x80c6330) at connections.c:1435
#5  0x0805581c in network_server_handle_fdevent (s=0x8074008, context=0x80b5c70, revents=1) at network.c:52
#6  0x0804f87a in main (argc=4, argv=0xbffff7c4) at server.c:1446
(gdb) print etag
$5 = (buffer *) 0x812d0d0
(gdb) print *etag
$6 = {ptr = 0x0, used = 0, size = 0}
(gdb) print etag->used -1
$7 = 4294967295
(gdb) quit

mod_compress needs a way to know if the cached file is still valid, and it is using etag for this. so no etag => no cache in mod_compress (you can still use mod_compress, but not with the cache).
And i don't recommend using the size alone for etag, as you perhaps sometimes change your files without changing the size.

good job on the backtrace; that is always a good start to fix problems with segfauls and aborts.

I think cache can be used, but internally, on the server, ETag should not be transfered to the user accesing the page (Since i set the Expires to be "access plus 10 years" or something like that. But if i configure to remove Etags, i mean from the server response not if used for cache internally.