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diff --git a/README b/README new file mode 100644 index 0000000..5917c37 --- a/dev/null +++ b/ README |
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1 | Cache algorithm |
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2 | =============== |
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3 | |
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4 | Cgit normally returns cached pages when invoked. If there is no cache file, or |
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5 | the cache file has expired, it is regenerated. Finally, the cache file is |
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6 | printed on stdout. |
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7 | |
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8 | When it is decided that a cache file needs to be regenerated, an attempt is |
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9 | made to create a corresponding lockfile. If this fails, the process gives up |
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10 | and uses the expired cache file instead. |
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11 | |
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12 | When there is no cache file for a request, an attempt is made to create a |
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13 | corresponding lockfile. If this fails, the process calls sched_yield(2) before |
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14 | restarting the request handling. |
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15 | |
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16 | In pseudocode: |
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17 | |
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18 | name = generate_cache_name(request); |
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19 | top: |
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20 | if (!exists(name)) { |
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21 | if (lock_cache(name)) { |
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22 | generate_cache(request, name); |
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23 | unlock_cache(name); |
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24 | } else { |
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25 | sched_yield(); |
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26 | goto top; |
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27 | } |
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28 | } else if (expired(name)) { |
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29 | if (lock_cache(name)) { |
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30 | generate_cache(request, name); |
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31 | unlock_cache(name); |
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32 | } |
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33 | } |
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34 | print_file(name); |
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35 | |
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36 | |
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37 | The following options can be set in /etc/cgitrc to control cache behaviour: |
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38 | cache-root: root directory for cache files |
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39 | cache-root-ttl: TTL for the repo listing page |
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40 | cache-repo-ttl: TTL for any repos summary page |
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41 | cache-dynamic-ttl: TTL for pages with symbolic references (not SHA1) |
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42 | cache-static-ttl: TTL for pages with sha1 references |
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43 | |
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44 | TTL is specified in minutes, -1 meaning "infinite caching". |
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45 | |
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46 | |
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47 | Naming of cache files |
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48 | --------------------- |
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49 | Repository listing: <cachedir>/index.html |
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50 | Repository summary: <cachedir>/<repo>/index.html |
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51 | Repository subpage: <cachedir>/<repo>/<page>/<querystring>.html |
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52 | |
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53 | The corresponding lock files have a ".lock" suffix. |
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54 | |
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