cgit with patches for sandboxing using qssb
25105d7eca
This enables internal caching of page output. Page requests are split into four groups: 1) repo listing (front page) 2) repo summary 3) repo pages w/symbolic references in query string 4) repo pages w/constant sha1's in query string Each group has a TTL specified in minutes. When a page is requested, a cached filename is stat(2)'ed and st_mtime is compared to time(2). If TTL has expired (or the file didn't exist), the cached file is regenerated. When generating a cached file, locking is used to avoid parallell processing of the request. If multiple processes tries to aquire the same lock, the ones who fail to get the lock serves the (expired) cached file. If the cached file don't exist, the process instead calls sched_yield(2) before restarting the request processing. Signed-off-by: Lars Hjemli <hjemli@gmail.com> |
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|---|---|---|
| .gitignore | ||
| cache.c | ||
| cgit.c | ||
| cgit.css | ||
| cgit.h | ||
| config.c | ||
| git.h | ||
| html.c | ||
| Makefile | ||
| README | ||
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.