----- Original Message ----- > > Am 06.10.2011 19:03, schrieb Amila Liyanaarachchi: > > Hi Dev, > > > > I'm working on a caching protocol similar to HTTP on a different > > research. I have the following question regarding > > the e-tags. > > When does exactly apache computes the e-tag for a certain resource? > > Does it compute that when there is a request for that particular > > resource or is it computed by the server whenever > > a resource get modified in the server? > > request time because it normally contains the inode
Which makes it quite useless in a farm with multiple servers as the same files will have different inodes. My recomendation is to use size and mtime: http://httpd.apache.org/docs/current/mod/core.html#fileetag ETag is then an MD5 sum of a combination of all values considered. Be wary that the calculation of the ETag can sometimes take more effort than just delivering the ETag. See Theo Schlossnagle's performance talks for reference: http://omniti.com/seeds/yslow-to-yfast-in-45-minutes http://lethargy.org/~jesus/writes/web-performance-boot-camp i -- Igor Galić Tel: +43 (0) 664 886 22 883 Mail: [email protected] URL: http://brainsware.org/ GPG: 571B 8B8A FC97 266D BDA3 EF6F 43AD 80A4 5779 3257
