Diffstat (limited to 'README')
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1 files changed, 41 insertions, 86 deletions
@@ -1,99 +1,54 @@ -cgit - CGI for Git -================== +Cache algorithm +=============== -This is an attempt to create a fast web interface for the Git SCM, using a -built-in cache to decrease server I/O pressure. +Cgit normally returns cached pages when invoked. If there is no cache file, or +the cache file has expired, it is regenerated. Finally, the cache file is +printed on stdout. -Installation ------------- +When it is decided that a cache file needs to be regenerated, an attempt is +made to create a corresponding lockfile. If this fails, the process gives up +and uses the expired cache file instead. -Building cgit involves building a proper version of Git. How to do this -depends on how you obtained the cgit sources: +When there is no cache file for a request, an attempt is made to create a +corresponding lockfile. If this fails, the process calls sched_yield(2) before +restarting the request handling. -a) If you're working in a cloned cgit repository, you first need to -initialize and update the Git submodule: +In pseudocode: - $ git submodule init # register the Git submodule in .git/config - $ $EDITOR .git/config # if you want to specify a different url for git - $ git submodule update # clone/fetch and checkout correct git version + name = generate_cache_name(request); +top: + if (!exists(name)) { + if (lock_cache(name)) { + generate_cache(request, name); + unlock_cache(name); + } else { + sched_yield(); + goto top; + } + } else if (expired(name)) { + if (lock_cache(name)) { + generate_cache(request, name); + unlock_cache(name); + } + } + print_file(name); -b) If you're building from a cgit tarball, you can download a proper git -version like this: - $ make get-git +The following options can be set in /etc/cgitrc to control cache behaviour: + cache-root: root directory for cache files + cache-root-ttl: TTL for the repo listing page + cache-repo-ttl: TTL for any repos summary page + cache-dynamic-ttl: TTL for pages with symbolic references (not SHA1) + cache-static-ttl: TTL for pages with sha1 references -When either a) or b) has been performed, you can build and install cgit like -this: +TTL is specified in minutes, -1 meaning "infinite caching". - $ make - $ sudo make install -This will install `cgit.cgi` and `cgit.css` into `/var/www/htdocs/cgit`. You -can configure this location (and a few other things) by providing a `cgit.conf` -file (see the Makefile for details). - -If you'd like to compile without Lua support, you may use: - - $ make NO_LUA=1 - -And if you'd like to specify a Lua implementation, you may use: - - $ make LUA_PKGCONFIG=lua5.1 - -If this is not specified, the Lua implementation will be auto-detected, -preferring LuaJIT if many are present. Acceptable values are generally "lua", -"luajit", "lua5.1", and "lua5.2". - - -Dependencies ------------- - -* libzip -* libcrypto (OpenSSL) -* libssl (OpenSSL) -* optional: luajit or lua, most reliably used when pkg-config is available - -Apache configuration --------------------- - -A new `Directory` section must probably be added for cgit, possibly something -like this: - - <Directory "/var/www/htdocs/cgit/"> - AllowOverride None - Options +ExecCGI - Order allow,deny - Allow from all - </Directory> - - -Runtime configuration +Naming of cache files --------------------- +Repository listing: <cachedir>/index.html +Repository summary: <cachedir>/<repo>/index.html +Repository subpage: <cachedir>/<repo>/<page>/<querystring>.html -The file `/etc/cgitrc` is read by cgit before handling a request. In addition -to runtime parameters, this file may also contain a list of repositories -displayed by cgit (see `cgitrc.5.txt` for further details). - -The cache ---------- - -When cgit is invoked it looks for a cache file matching the request and -returns it to the client. If no such cache file exists (or if it has expired), -the content for the request is written into the proper cache file before the -file is returned. - -If the cache file has expired but cgit is unable to obtain a lock for it, the -stale cache file is returned to the client. This is done to favour page -throughput over page freshness. - -The generated content contains the complete response to the client, including -the HTTP headers `Modified` and `Expires`. - -Online presence ---------------- - -* The cgit homepage is hosted by cgit at <https://git.zx2c4.com/cgit/about/> +The corresponding lock files have a ".lock" suffix. -* Patches, bug reports, discussions and support should go to the cgit - mailing list: <cgit@lists.zx2c4.com>. To sign up, visit - <https://lists.zx2c4.com/mailman/listinfo/cgit> |