ExternalStoreAccess.php

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<?php
use MediaWiki\Exception\ReadOnlyError;
use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use Wikimedia\RequestTimeout\TimeoutException;
 
class ExternalStoreAccess implements LoggerAwareInterface {
    private $storeFactory;
    private $logger;
 
    public function __construct( ExternalStoreFactory $factory, ?LoggerInterface $logger = null ) {
        $this->storeFactory = $factory;
        $this->logger = $logger ?: new NullLogger();
    }
 
    public function setLogger( LoggerInterface $logger ) {
        $this->logger = $logger;
    }
 
    public function fetchFromURL( $url, array $params = [] ) {
        return $this->storeFactory->getStoreForUrl( $url, $params )->fetchFromURL( $url );
    }
 
    public function fetchFromURLs( array $urls, array $params = [] ) {
        $batches = $this->storeFactory->getUrlsByProtocol( $urls );
        $retval = [];
        foreach ( $batches as $proto => $batchedUrls ) {
            $store = $this->storeFactory->getStore( $proto, $params );
            $retval += $store->batchFetchFromURLs( $batchedUrls );
        }
        // invalid, not found, db dead, etc.
        $missing = array_diff( $urls, array_keys( $retval ) );
        foreach ( $missing as $url ) {
            $retval[$url] = false;
        }
 
        return $retval;
    }
 
    public function insert( $data, array $params = [], ?array $tryStores = null ) {
        $tryStores ??= $this->storeFactory->getWriteBaseUrls();
        if ( !$tryStores ) {
            throw new ExternalStoreException( "List of external stores provided is empty." );
        }
 
        $error = false;      // track the last exception thrown
        $readOnlyCount = 0;  // track if a store was read-only
        while ( count( $tryStores ) > 0 ) {
            $index = mt_rand( 0, count( $tryStores ) - 1 );
            $storeUrl = $tryStores[$index];
 
            $this->logger->debug( __METHOD__ . ": trying $storeUrl" );
 
            $store = $this->storeFactory->getStoreForUrl( $storeUrl, $params );
            if ( $store === false ) {
                throw new ExternalStoreException( "Invalid external storage protocol - $storeUrl" );
            }
 
            $location = $this->storeFactory->getStoreLocationFromUrl( $storeUrl );
            try {
                if ( $store->isReadOnly( $location ) ) {
                    $readOnlyCount++;
                    $msg = 'read only';
                } else {
                    $url = $store->store( $location, $data );
                    if ( $url !== false && $url !== '' ) {
                        // A store accepted the write; done!
                        return $url;
                    }
                    throw new ExternalStoreException(
                        "No URL returned by storage medium ($storeUrl)"
                    );
                }
            } catch ( TimeoutException $e ) {
                throw $e;
            } catch ( Exception $ex ) {
                $error = $ex;
                $msg = 'caught ' . get_class( $error ) . ' exception: ' . $error->getMessage();
            }
 
            unset( $tryStores[$index] ); // Don't try this one again!
            $tryStores = array_values( $tryStores ); // Must have consecutive keys
            $this->logger->error(
                "Unable to store text to external storage {store_path} ({failure})",
                [ 'store_path' => $storeUrl, 'failure' => $msg ]
            );
        }
 
        // We only get here when all stores failed.
        if ( $error ) {
            // At least one store threw an exception. Re-throw the most recent one.
            throw $error;
        } elseif ( $readOnlyCount ) {
            // If no exceptions where thrown and we get here,
            // this should mean that all stores were in read-only mode.
            throw new ReadOnlyError();
        } else {
            // We shouldn't get here. If there were no failures, this method should have returned
            // from inside the body of the loop.
            throw new LogicException( "Unexpected failure to store text to external store" );
        }
    }
 
    public function isReadOnly( $storeUrls = null ) {
        if ( $storeUrls === null ) {
            $storeUrls = $this->storeFactory->getWriteBaseUrls();
        } else {
            $storeUrls = is_array( $storeUrls ) ? $storeUrls : [ $storeUrls ];
        }
 
        if ( !$storeUrls ) {
            return false; // no stores exists which can be "read only"
        }
 
        foreach ( $storeUrls as $storeUrl ) {
            $store = $this->storeFactory->getStoreForUrl( $storeUrl );
            $location = $this->storeFactory->getStoreLocationFromUrl( $storeUrl );
            if ( $store !== false && !$store->isReadOnly( $location ) ) {
                return false; // at least one store is not read-only
            }
        }
 
        return true; // all stores are read-only
    }
}