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-rw-r--r--README87
1 files changed, 34 insertions, 53 deletions
diff --git a/README b/README
index 5917c37..010dd5c 100644
--- a/README
+++ b/README
@@ -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