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| 1 | <?php |
| 2 | |
| 3 | namespace GrowthExperiments; |
| 4 | |
| 5 | use MediaWiki\User\CentralId\CentralIdLookup; |
| 6 | use MediaWiki\User\UserIdentity; |
| 7 | use Psr\Log\LoggerInterface; |
| 8 | |
| 9 | /** |
| 10 | * Service for assigning experiment / variant to users using configured |
| 11 | * variants in conditional user options. |
| 12 | * @see https://www.mediawiki.org/wiki/Manual:$wgConditionalUserOptions |
| 13 | */ |
| 14 | class ExperimentUserDefaultsManager { |
| 15 | |
| 16 | public const CUCOND_BUCKET_BY_USER_ID = 'user-bucket-growth'; |
| 17 | |
| 18 | private LoggerInterface $logger; |
| 19 | |
| 20 | /** |
| 21 | * CentralIdLookup must be provided as a callback function to avoid circular dependency |
| 22 | * @var callable |
| 23 | */ |
| 24 | private $centralIdLookupCallback; |
| 25 | |
| 26 | public function __construct( LoggerInterface $logger, callable $centralIdLookupCallback ) { |
| 27 | $this->logger = $logger; |
| 28 | $this->centralIdLookupCallback = $centralIdLookupCallback; |
| 29 | } |
| 30 | |
| 31 | /** |
| 32 | * @param UserIdentity $userIdentity The user being evaluated |
| 33 | * @param string $experimentName The name of the experiment |
| 34 | * @param array $args An array with the condition arguments. |
| 35 | * @return bool Whether the user option being evaluated (bucket) should be returned as the default |
| 36 | */ |
| 37 | public function shouldAssignBucket( UserIdentity $userIdentity, string $experimentName, array $args ): bool { |
| 38 | $centralIdLookupCallback = $this->centralIdLookupCallback; |
| 39 | /** @var CentralIdLookup */ |
| 40 | $centralIdLookup = $centralIdLookupCallback(); |
| 41 | $userCentralId = $centralIdLookup->centralIdFromLocalUser( $userIdentity ); |
| 42 | if ( $userCentralId === 0 ) { |
| 43 | // CentralIdLookup is documented to return a zero on failure |
| 44 | // TODO: Increase severity back to error, once it stops happening so frequently (T380271) |
| 45 | $this->logger->debug( __METHOD__ . ' failed to get a central user ID', [ |
| 46 | 'exception' => new \RuntimeException, |
| 47 | 'userName' => $userIdentity->getName(), |
| 48 | ] ); |
| 49 | // No point in hashing an error code |
| 50 | return false; |
| 51 | } |
| 52 | $sample = $this->getSample( $userCentralId, $experimentName ); |
| 53 | return $this->isInSample( $args[0], $sample ); |
| 54 | } |
| 55 | |
| 56 | /** |
| 57 | * @param int $bucketRatio The probability rate for the bucket to be assigned |
| 58 | * @param int $sample The sample to test against |
| 59 | * @return bool Whether the sample is within the bucket ratio |
| 60 | */ |
| 61 | private function isInSample( int $bucketRatio, int $sample ): bool { |
| 62 | return $sample < $bucketRatio; |
| 63 | } |
| 64 | |
| 65 | private function getSample( int $userCentralId, string $experimentName ): int { |
| 66 | $floatHash = $this->getUserHash( $userCentralId, $experimentName ); |
| 67 | return (int)( fmod( $floatHash, 1 ) * 100 ); |
| 68 | } |
| 69 | |
| 70 | /** |
| 71 | * Get hash of a user ID as a float between 0.0 (inclusive) and 1.0 (non-inclusive) |
| 72 | * concatenated with an experiment name. |
| 73 | * |
| 74 | * Originally taken from MediaWiki\Extension\MetricsPlatform\UserSplitter\UserSplitterInstrumentation. |
| 75 | * |
| 76 | * @param int $userId The user's id to hash |
| 77 | * @param string $experimentName The name of the experiment the bucketing applies |
| 78 | * @return float Float between 0.0 (inclusive) and 1.0 (non-inclusive) representing a user's hash |
| 79 | */ |
| 80 | private function getUserHash( int $userId, string $experimentName ): float { |
| 81 | $userIdExperimentName = $userId . $experimentName; |
| 82 | return intval( substr( md5( $userIdExperimentName ), 0, 6 ), 16 ) / ( 0xffffff + 1 ); |
| 83 | } |
| 84 | |
| 85 | } |