f37cee996e
Modules now track their version via getVersionHash() instead of getModifiedTime(). == Background == While some resources have observeable timestamps (e.g. files stored on disk), many other resources do not. E.g. config variables, and module definitions. For static file modules, one can e.g. revert one of more files in a module to a previous version and not affect the max timestamp. Wiki modules include pages only if they exist. The user module supports common.js and skin.js. By default neither exists. If a user has both, and then the less-recently modified one is deleted, the max-timestamp remains unchanged. For client-side caching, batch requests use "Math.max" on the relevant timestamps. Again, if a module changes but another module is more recent (e.g. out-of-order deployment, or out-of-order discovery), the change would not result in a cache miss. More scenarios can be found in the associated Phabricator tasks. == Version hash == Previously we virtually mapped these variables to a timestamp by storing the current time alongside a hash of the value in ObjectCache. Considering the number of possible request contexts (wikis * modules * users * skins * languages) this doesn't work well. It results in needless cache invalidation when the first time observation is purged due to LRU algorithms. It also has other minor bugs leading to fewer cache hits. All modules automatically get the benefits of version hashing with this change. The old getDefinitionMtime() and getHashMtime() have been replaced with dummies that return 1. These functions are often called from getModifiedTime() in subclasses. For backward-compatibility, their respective values (definition summary and hash) are now included in getVersionHash directly. As examples, the following modules have been updated to use getVersionHash directly. Other modules still work fine and can be updated later. * ResourceLoaderFileModule * ResourceLoaderEditToolbarModule * ResourceLoaderStartUpModule * ResourceLoaderWikiModule The presence of hashes in place of timestamps increases the startup module size on a default MediaWiki install from 4.4k to 5.8k (after gzip and minification). == ETag == Since timestamps are no longer tracked, we need a different way to implement caching for cache proxies (e.g. Varnish) and web browsers. Previously we used the Last-Modified header (in combination with Cache-Control and Expires). Instead of Last-Modified (and If-Modified-Since), we use ETag (and If-None-Match). Entity tags (new in HTTP/1.1) are much stricter than Last-Modified by default. They instruct browsers to allow usage of partial Range requests. Since our responses are dynamically generated, we need to use the Weak version of ETag. While this sounds bad, it's no different than Last-Modified. As reassured by RFC 2616 <http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.3.3> the specified behaviour behind Last-Modified follows the same "Weak" caching logic as Entity tags. It's just that entity tags are capable of a stricter mode (whereas Last-Modified is inherently weak). == File cache == If $wgUseFileCache is enabled, ResourceLoader uses ResourceFileCache to cache load.php responses. While the blind TTL handling (during the allowed expiry period) is still maxage/timestamp based, tryRespondNotModified() now requires the caller to know the expected ETag. For this to work, the FileCache handling had to be moved from the top of ResoureLoader::respond() to after the expected ETag is computed. This also allows us to remove the duplicate tryRespondNotModified() handling since that's is already handled by ResourceLoader::respond() meanwhile. == Misc == * Remove redundant modifiedTime cache in ResourceLoaderFileModule. * Change bugzilla references to Phabricator. * Centralised inclusion of wgCacheEpoch using getDefinitionSummary. Previously this logic was duplicated in each place the modified timestamp was used. * It's easy to forget calling the parent class in getDefinitionSummary(). Previously this method only tracked 'class' by default. As such, various extensions hardcoded that one value instead of calling the parent and extending the array. To better prevent this in the future, getVersionHash() now asserts that the '_cacheEpoch' property made it through. * tests: Don't use getDefinitionSummary() as an API. Fix ResourceLoaderWikiModuleTest to call getPages properly. * In tests, the default timestamp used to be 1388534400000 (which is the unix time of 20140101000000; the unit tests' CacheEpoch). The new version hash of these modules is "XyCC+PSK", which is the base64 encoded prefix of the SHA1 digest of: '{"_class":"ResourceLoaderTestModule","_cacheEpoch":"20140101000000"}' * Add sha1.js library for client-side hash generation. Compared various different implementations for code size (after minfication/gzip), and speed (when used for short hexidecimal strings). https://jsperf.com/sha1-implementations - CryptoJS <https://code.google.com/p/crypto-js/#SHA-1> (min+gzip: 2.5k) http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/sha1.js Chrome: 45k, Firefox: 89k, Safari: 92k - jsSHA <https://github.com/Caligatio/jsSHA> https://github.com/Caligatio/jsSHA/blob/3c1d4f2e/src/sha1.js (min+gzip: 1.8k) Chrome: 65k, Firefox: 53k, Safari: 69k - phpjs-sha1 <https://github.com/kvz/phpjs> (RL min+gzip: 0.8k) https://github.com/kvz/phpjs/blob/1eaab15d/functions/strings/sha1.js Chrome: 200k, Firefox: 280k, Safari: 78k Modern browsers implement the HTML5 Crypto API. However, this API is asynchronous, only enabled when on HTTPS in Chromium, and is quite low-level. It requires boilerplate code to actually use with TextEncoder, ArrayBuffer and Uint32Array. Due this being needed in the module loader, we'd have to load the fallback regardless. Considering this is not used in a critical path for performance, it's not worth shipping two implementations for this optimisation. May also resolve: * T44094 * T90411 * T94810 Bug: T94074 Change-Id: Ibb292d2416839327d1807a66c78fd96dac0637d0 |
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| .. | ||
| data | ||
| docs | ||
| includes | ||
| languages | ||
| maintenance | ||
| mocks | ||
| skins | ||
| structure | ||
| suites | ||
| tests | ||
| bootstrap.php | ||
| LessFileCompilationTest.php | ||
| Makefile | ||
| MediaWikiLangTestCase.php | ||
| MediaWikiPHPUnitTestListener.php | ||
| MediaWikiTestCase.php | ||
| phpunit.php | ||
| README | ||
| ResourceLoaderTestCase.php | ||
| run-tests.bat | ||
| suite.xml | ||
| TODO | ||
== MediaWiki PHPUnit Tests == The unit tests for MediaWiki are implemented using the PHPUnit testing framework and require PHPUnit to run. === WARNING === Some of the unit tests are DESTRUCTIVE and WILL ALTER YOUR WIKI'S CONTENTS. DO NOT RUN THESE TESTS ON A PRODUCTION SYSTEM OR ON ANY SYSTEM WHERE YOU NEED TO RETAIN YOUR DATA. == Installation == If PHPUnit is not installed, follow the installation instructions in the PHPUnit Manual at: http://www.phpunit.de/manual/current/en/installation.html - or - On Unix-like operating systems, run: make install == Running tests == The tests are run from your operating system's command line. Ensure that you are in the tests/phpunit directory of your MediaWiki installation. On Unix-like operating systems, the tests runs are controlled with a makefile. Run command: make help for a full list of options for running tests. On Windows-family operating systems, run the 'run-tests.bat' batch file. === Writing tests === A guide to writing unit tests for MediaWiki can be found at: http://mediawiki.org/wiki/Unit_Testing