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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.

td>June McEnroe I'm going to recreate it from fresh sh sources for clean git history. 2020-03-08Add The Stone SkyJune McEnroe 2020-03-08Publish "How I Relay Chat"June McEnroe 2020-03-03Don't use $ inside $(())June McEnroe 2020-03-03Remove setoptJune McEnroe 2020-03-03Use getopts in shell scriptsJune McEnroe WTF why did no one tell me about this? 2020-02-27Style %T outside of Rs in italicJune McEnroe 2020-02-26Add Fierce Femmes and Notorious LiarsJune McEnroe 2020-02-23Add This Is How You Lose the Time WarJune McEnroe 2020-02-22Add See Ya LaterJune McEnroe 2020-02-20Remove wiki scriptJune McEnroe Wikipedia seems to have removed the one-sentence extracts from the opensearch results. Too bad. It's not a wiki script, what we need is a command that fetches single-sentence summaries of articles on Wikipedia. 2020-02-19Add The Obelisk GateJune McEnroe 2020-02-17Add Four Tet — HandsJune McEnroe One from the cafe that caught my attention. 2020-02-12Simplify macOS notify-sendJune McEnroe 2020-02-12Add imbox and notemap to pageJune McEnroe 2020-02-12Collapse simple linksJune McEnroe 2020-02-12Move catgirl up the pageJune McEnroe 2020-02-12Update catgirl pty grabJune McEnroe 2020-02-12Link to cgit /about pages where appropriateJune McEnroe 2020-02-11Separate LINKS from BINS for html to workJune McEnroe 2020-02-11Add margin to Bl-bullet itemsJune McEnroe 2020-02-10Match URLs inside parens or with paired parens insideJune McEnroe 2020-02-10Duplicate effective URL before passing it back to curlJune McEnroe Apparently sometimes it didn't like receiving its own internal storage to parse again. Understandable. 2020-02-09Add To Be Taught, If FortunateJune McEnroe 2020-02-04Add The Future of Another TimelineJune McEnroe Wow. One of the best I've read. 2020-01-31Reorganize the Makefile for the umpteenth timeJune McEnroe Broke out LDLIBS for each bin, and made everything more uniform. 2020-01-28Change scout sensitivity to 1.4June McEnroe idk it seems to work. 2020-01-28Import shows.txtJune McEnroe