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| -rw-r--r-- | README | 87 |
1 files changed, 34 insertions, 53 deletions
@@ -1,54 +1,35 @@ -Cache algorithm -=============== - -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. - -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. - -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. - -In pseudocode: - - 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); - - -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 - -TTL is specified in minutes, -1 meaning "infinite caching". - - -Naming of cache files ---------------------- -Repository listing: <cachedir>/index.html -Repository summary: <cachedir>/<repo>/index.html -Repository subpage: <cachedir>/<repo>/<page>/<querystring>.html - -The corresponding lock files have a ".lock" suffix. + cgit - cgi for git + + +This is an attempt to create a fast web interface for the git scm, using a +frontside cache to decrease server io-pressure. + +When cgit is invoked, it looks for a cached page matching the request. If no +such cachefile exist (or it has expired), it is (re)generated. Finally, the +cachefile is returned to the client. + +If the cachefile has expired, but cgit is unable to lock the cachefile, the +client will get the stale cachefile after all. This is done to favour page +throughput over page freshness. + +Also, when a cachefile is generated, a few cache-related http-headers are +created: "Modified" is set to current time(2), while "Expires" is set to +time(2) + <cachefile TTL> * 60 (unless the TTL is negative, in which case it +is read as "60 * 60 * 24 * 365"). This is done to avoid repeated requests for +already visited pages. + +The following cache-related options can be set in /etc/cgitrc: + + cache-root=<path> root directory for cache files + cache-root-ttl=<min> TTL for the repo listing page + cache-repo-ttl=<min> TTL for repo summary pages + cache-dynamic-ttl=<min> TTL for pages with symbolic references + cache-static-ttl=<min> TTL for pages with sha1 references + +The cachefiles are split into different directories, based on the requested +repository and page: + + Repo listing: <cachedir>/index.html + Repo summary: <cachedir>/<repo>/index.html + Repo subpage: <cachedir>/<repo>/<page>/<querystring>.html |