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resourceloader: Shorten cache expiry if 'version' query doesn't match

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Versioned load.php requests (load.php?modules=..&version=..) are highly
cacheable due to being versioned. When a module changes, the startup module
delivers new metadata to the client which naturally results in a cache miss
by producing a different url.

However, during upgrades and other deployments it was possible for a
multi-server installation to pollute edge caches with outdated content
in the following scenario:

* Deployment starts for an upgrade from version A to version B.
* Server 1 (on version B) gets a request for the startup manifest.
  Client receives new manifest with version B information
  and makes a versioned request for version B.
* Server 2 (still on version A) responds to this request with the
  version it has (which is version A).
* Edge cache will store version A under the new url for version B.

This commit changes the last point by setting a low max-age when a request
has a 'version' hash mismatch.

Test plan:
* Look for a request in your browser like:
 '/load.php?..modules=jquery%2Cmediawiki..&version=..'
* Verify it has a high Cache-Control max-age.
* Manipulate the 'version' parameter and verify it gets a low max-age.

Bug: T117587
Change-Id: Iba89c09b7b71d9fd2a8ff3ebe2618e26ea9daddf
This commit is contained in:
Timo Tijhof 2016-09-02 15:44:59 -07:00 committed by Krinkle
parent a0c9fb59a9
commit 6fa1e56daa
1 changed files with 45 additions and 9 deletions
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54
includes/resourceloader/ResourceLoader.php
View file

@ -610,17 +610,49 @@ class ResourceLoader implements LoggerAwareInterface {
*
* @since 1.26
* @param ResourceLoaderContext $context
* @param array $modules List of ResourceLoaderModule objects
* @param string[] $modules List of known module names
* @return string Hash
*/
public function getCombinedVersion( ResourceLoaderContext $context, array $modules ) {
if ( !$modules ) {
public function getCombinedVersion( ResourceLoaderContext $context, array $moduleNames ) {
if ( !$moduleNames ) {
return '';
}
$hashes = array_map( function ( $module ) use ( $context ) {
return $this->getModule( $module )->getVersionHash( $context );
}, $modules );
return self::makeHash( implode( $hashes ) );
}, $moduleNames );
return self::makeHash( implode( '', $hashes ) );
}
/**
* Get the expected value of the 'version' query parameter.
*
* This is used by respond() to set a short Cache-Control header for requests with
* information newer than the current server has. This avoids pollution of edge caches.
* Typically during deployment. (T117587)
*
* This MUST match return value of `mw.loader#getCombinedVersion()` client-side.
*
* @since 1.28
* @param ResourceLoaderContext $context
* @param string[] $modules List of module names
* @return string Hash
*/
public function getExpectedVersionQuery( ResourceLoaderContext $context ) {
// As of MediaWiki 1.28, the server and client use the same algorithm for combining
// version hashes. There is no technical reason for this to be same, and for years the
// implementations differed. If getCombinedVersion in PHP (used for StartupModule and
// E-Tag headers) differs in the future from getCombinedVersion in JS (used for 'version'
// query parameter), then this method must continue to match the JS one.
$moduleNames = [];
foreach ( $context->getModules() as $name ) {
if ( !$this->getModule( $name ) ) {
// If a versioned request contains a missing module, the version is a mismatch
// as the client considered a module (and version) we don't have.
return '';
}
$moduleNames[] = $name;
}
return $this->getCombinedVersion( $context, $moduleNames );
}
/**
@ -759,10 +791,14 @@ class ResourceLoader implements LoggerAwareInterface {
*/
protected function sendResponseHeaders( ResourceLoaderContext $context, $etag, $errors ) {
$rlMaxage = $this->config->get( 'ResourceLoaderMaxage' );
// If a version wasn't specified we need a shorter expiry time for updates
// to propagate to clients quickly
// If there were errors, we also need a shorter expiry time so we can recover quickly
if ( is_null( $context->getVersion() ) || $errors ) {
// Use a short cache expiry so that updates propagate to clients quickly, if:
// - No version specified (shared resources, e.g. stylesheets)
// - There were errors (recover quickly)
// - Version mismatch (T117587, T47877)
if ( is_null( $context->getVersion() )
|| $errors
|| $context->getVersion() !== $this->getExpectedVersionQuery( $context )
) {
$maxage = $rlMaxage['unversioned']['client'];
$smaxage = $rlMaxage['unversioned']['server'];
// If a version was specified we can use a longer expiry time since changing