Lars Hjemli [Tue, 12 Dec 2006 09:16:41 +0000 (10:16 +0100)]
cache_lock: do xstrdup/free on lockfile
Since fmt() uses 8 alternating static buffers, and cache_lock might call
cache_create_dirs() multiple times, which in turn might call fmt() twice,
after four iterations lockfile would be overwritten by a cachedirectory
path.
In worst case, this could cause the cachedirectory to be unlinked and replaced
by a cachefile.
Fix: use xstrdup() on the result from fmt() before assigning to lockfile, and
call free(lockfile) before exit.
Lars Hjemli [Mon, 11 Dec 2006 21:53:50 +0000 (22:53 +0100)]
Don't truncate valid cachefiles
An embarrassing thinko in cgit_check_cache() would truncate valid cachefiles
in the following situation:
1) process A notices a missing/expired cachefile
2) process B gets scheduled, locks, fills and unlocks the cachefile
3) process A gets scheduled, locks the cachefile, notices that the cachefile
now exist/is not expired anymore, and continues to overwrite it with an
empty lockfile.
Lars Hjemli [Mon, 11 Dec 2006 11:10:12 +0000 (12:10 +0100)]
Avoid infinite loops in caching layer
Add a global variable, cgit_max_lock_attemps, to avoid the possibility of
infinite loops when failing to acquire a lockfile. This could happen on
broken setups or under crazy server load.
Incidentally, this also fixes a lurking bug in cache_lock() where an
uninitialized returnvalue was used.
Lars Hjemli [Sun, 10 Dec 2006 21:31:36 +0000 (22:31 +0100)]
Add caching infrastructure
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.
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