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
This makes it easier for subclasses to use ResourceLoaderWikiModule. Currently
many subclasses of this simply need to override the getPages() method.
UserModule and SiteModule keep their getPages override due to the set of pages
being dependent on context.
Change-Id: I388531398671afacfec36c6c5746d72267b5bdac
Mock calls to ResourceLoaderContext::getDirection(), which creates
Language objects to get the directionality of a language.
Change-Id: Ibe6da3013e658aa7cf596c1da2f8ca1314b7cdd3
Follows-up 9272bc6c47, 03c503da22, 1e063f6078.
One can't wrap arbitrary JavaScript in an if-statement and have
its inner-body mean exactly the same.
Certain statements are only allowed in the top of a scope (such
as hoisted function declarations). These are not allowed inside
a block. They're fine in both global scope and local function
scope, but not inside an if-block of any scope.
The ECMAScript spec only describes what is an allowed token.
Any unexpected token should result in a SyntaxError.
Chrome's implementation (V8) allows function declarations in
blocks and hoists them to *outside* the condition. Firefox's
SpiderMonkey silently ignores the statement. Neither throw a
SyntaxError.
Rgular ResourceLoader responses only contain mw.loader.implement()
and mw.loader.state() call which could be wrapped without issues.
However such responses don't need wrapping as they're only made
by mediawiki.js (in which case mw is obviously loaded). The
wrapping is for legacy scripts that execute in the global scope.
For those, let's wrap the script tag itself (instead of the
response). That seems like the most water-tight and semantically
correct solution.
Had to bring in $isRaw from ResourceLoader.php, else the startup
module would have been wrapped as well (added regression test).
Bug: 69924
Change-Id: Iedda0464f734ba5f7a884726487f6c7e07d444f1
In most cases, we just check whether the pages exist before saying
the module is not empty to avoid generating cached HTML without
the appropriate <script> or <link> tags.
However, for modules in the 'user' group, normal users cannot
delete their personal JavaScript/CSS pages, causing needless
extra requests, even though we know the pages are empty.
ResourceLoader::isKnownEmpty() now checks the page_len field
for modules in the 'user' group to check that there is
some actual content.
Bug: 68488
Change-Id: I0570f62887fd4642fd60367ae0b51d7dc19488ca
Given that we have entirely separate code for handling one and the
other, and given the nature of code comments stuffed inside other
structures, this isn't really obvious that they work.
And indeed, "/*@noflip*/ /*@embed*/" doesn't work (filed bug 69698).
Amazingly, all other combinations do.
Change-Id: Ie30bab251eb4abee122c783d057de4102e53d1fc
A module can be registered with a skip function. Such function,
if provided, will be invoked by the client when a module is
queued for loading. If the function returns true, the client will
bypass any further loading action and mark the module as 'ready'.
This can be used to implement a feature test for a module
providing a shim or polyfill.
* Change visibility of method ResourceLoader::filter to public.
So that it can be invoked by ResourceLoaderStartupModule.
* Add option to suppress the cache key report in ResourceLoader::filter.
We usually only call the minifier once on an entire request
reponse (because it's all concatenated javascript or embedded
javascript in various different closures, still valid as one
large script) and only add a little bottom line for the cache
key. When embedding the skip function we have to run the minifier
on them separately as they're output as strings (not actual
functions). These strings are typically quite small and blowing
up the response with loads of cache keys is not desirable in
production.
* Add method to clear the static cache of ResourceLoader::inDebugMode.
Global static state is evil but, as long as we have it, we at
least need to clear it after switching contexts in the test suite.
Also:
* Remove obsolete setting of 'debug=true' in the FauxRequest in
ResourceLoaderTestCase. It already sets global wgResourceLoaderDebug
in the setUp() method.
Bug: 66390
Change-Id: I87a0ea888d791ad39f114380c42e2daeca470961
Still quite a few were being minified unconditinally. This is in
preparation for adding unit tests for the startup module where
it'll make reading the unit tests (and looking at the diff in case
of a failure) a lot easier if the strings aren't minified.
Change-Id: Ia06787e0ce608fcafac4596c980606d06107f517
