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55 lines
1.6 KiB
55 lines
1.6 KiB
18 years ago
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Cache algorithm
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===============
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Cgit normally returns cached pages when invoked. If there is no cache file, or
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the cache file has expired, it is regenerated. Finally, the cache file is
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printed on stdout.
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When it is decided that a cache file needs to be regenerated, an attempt is
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made to create a corresponding lockfile. If this fails, the process gives up
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and uses the expired cache file instead.
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When there is no cache file for a request, an attempt is made to create a
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corresponding lockfile. If this fails, the process calls sched_yield(2) before
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restarting the request handling.
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In pseudocode:
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name = generate_cache_name(request);
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top:
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if (!exists(name)) {
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if (lock_cache(name)) {
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generate_cache(request, name);
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unlock_cache(name);
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} else {
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sched_yield();
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goto top;
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}
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} else if (expired(name)) {
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if (lock_cache(name)) {
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generate_cache(request, name);
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unlock_cache(name);
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}
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}
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print_file(name);
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The following options can be set in /etc/cgitrc to control cache behaviour:
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cache-root: root directory for cache files
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cache-root-ttl: TTL for the repo listing page
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cache-repo-ttl: TTL for any repos summary page
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cache-dynamic-ttl: TTL for pages with symbolic references (not SHA1)
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cache-static-ttl: TTL for pages with sha1 references
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TTL is specified in minutes, -1 meaning "infinite caching".
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Naming of cache files
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---------------------
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Repository listing: <cachedir>/index.html
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Repository summary: <cachedir>/<repo>/index.html
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Repository subpage: <cachedir>/<repo>/<page>/<querystring>.html
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The corresponding lock files have a ".lock" suffix.
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