Fix missing commit() flag in postgres savepoint class

[mediawiki.git] / includes / libs / filebackend / fileop / FileOp.php

<?php
/**
 * Helper class for representing operations with transaction support.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup FileBackend
 * @author Aaron Schulz
 */
use Psr\Log\LoggerInterface;

/**
 * FileBackend helper class for representing operations.
 * Do not use this class from places outside FileBackend.
 *
 * Methods called from FileOpBatch::attempt() should avoid throwing
 * exceptions at all costs. FileOp objects should be lightweight in order
 * to support large arrays in memory and serialization.
 *
 * @ingroup FileBackend
 * @since 1.19
 */
abstract class FileOp {
        /** @var array */
        protected $params = [];

        /** @var FileBackendStore */
        protected $backend;
        /** @var LoggerInterface */
        protected $logger;

        /** @var int */
        protected $state = self::STATE_NEW;

        /** @var bool */
        protected $failed = false;

        /** @var bool */
        protected $async = false;

        /** @var string */
        protected $batchId;

        /** @var bool Operation is not a no-op */
        protected $doOperation = true;

        /** @var string */
        protected $sourceSha1;

        /** @var bool */
        protected $overwriteSameCase;

        /** @var bool */
        protected $destExists;

        /* Object life-cycle */
        const STATE_NEW = 1;
        const STATE_CHECKED = 2;
        const STATE_ATTEMPTED = 3;

        /**
         * Build a new batch file operation transaction
         *
         * @param FileBackendStore $backend
         * @param array $params
         * @param LoggerInterface $logger PSR logger instance
         * @throws FileBackendError
         */
        final public function __construct(
                FileBackendStore $backend, array $params, LoggerInterface $logger
        ) {
                $this->backend = $backend;
                $this->logger = $logger;
                list( $required, $optional, $paths ) = $this->allowedParams();
                foreach ( $required as $name ) {
                        if ( isset( $params[$name] ) ) {
                                $this->params[$name] = $params[$name];
                        } else {
                                throw new InvalidArgumentException( "File operation missing parameter '$name'." );
                        }
                }
                foreach ( $optional as $name ) {
                        if ( isset( $params[$name] ) ) {
                                $this->params[$name] = $params[$name];
                        }
                }
                foreach ( $paths as $name ) {
                        if ( isset( $this->params[$name] ) ) {
                                // Normalize paths so the paths to the same file have the same string
                                $this->params[$name] = self::normalizeIfValidStoragePath( $this->params[$name] );
                        }
                }
        }

        /**
         * Normalize a string if it is a valid storage path
         *
         * @param string $path
         * @return string
         */
        protected static function normalizeIfValidStoragePath( $path ) {
                if ( FileBackend::isStoragePath( $path ) ) {
                        $res = FileBackend::normalizeStoragePath( $path );

                        return ( $res !== null ) ? $res : $path;
                }

                return $path;
        }

        /**
         * Set the batch UUID this operation belongs to
         *
         * @param string $batchId
         */
        final public function setBatchId( $batchId ) {
                $this->batchId = $batchId;
        }

        /**
         * Get the value of the parameter with the given name
         *
         * @param string $name
         * @return mixed Returns null if the parameter is not set
         */
        final public function getParam( $name ) {
                return isset( $this->params[$name] ) ? $this->params[$name] : null;
        }

        /**
         * Check if this operation failed precheck() or attempt()
         *
         * @return bool
         */
        final public function failed() {
                return $this->failed;
        }

        /**
         * Get a new empty predicates array for precheck()
         *
         * @return array
         */
        final public static function newPredicates() {
                return [ 'exists' => [], 'sha1' => [] ];
        }

        /**
         * Get a new empty dependency tracking array for paths read/written to
         *
         * @return array
         */
        final public static function newDependencies() {
                return [ 'read' => [], 'write' => [] ];
        }

        /**
         * Update a dependency tracking array to account for this operation
         *
         * @param array $deps Prior path reads/writes; format of FileOp::newPredicates()
         * @return array
         */
        final public function applyDependencies( array $deps ) {
                $deps['read'] += array_fill_keys( $this->storagePathsRead(), 1 );
                $deps['write'] += array_fill_keys( $this->storagePathsChanged(), 1 );

                return $deps;
        }

        /**
         * Check if this operation changes files listed in $paths
         *
         * @param array $deps Prior path reads/writes; format of FileOp::newPredicates()
         * @return bool
         */
        final public function dependsOn( array $deps ) {
                foreach ( $this->storagePathsChanged() as $path ) {
                        if ( isset( $deps['read'][$path] ) || isset( $deps['write'][$path] ) ) {
                                return true; // "output" or "anti" dependency
                        }
                }
                foreach ( $this->storagePathsRead() as $path ) {
                        if ( isset( $deps['write'][$path] ) ) {
                                return true; // "flow" dependency
                        }
                }

                return false;
        }

        /**
         * Get the file journal entries for this file operation
         *
         * @param array $oPredicates Pre-op info about files (format of FileOp::newPredicates)
         * @param array $nPredicates Post-op info about files (format of FileOp::newPredicates)
         * @return array
         */
        final public function getJournalEntries( array $oPredicates, array $nPredicates ) {
                if ( !$this->doOperation ) {
                        return []; // this is a no-op
                }
                $nullEntries = [];
                $updateEntries = [];
                $deleteEntries = [];
                $pathsUsed = array_merge( $this->storagePathsRead(), $this->storagePathsChanged() );
                foreach ( array_unique( $pathsUsed ) as $path ) {
                        $nullEntries[] = [ // assertion for recovery
                                'op' => 'null',
                                'path' => $path,
                                'newSha1' => $this->fileSha1( $path, $oPredicates )
                        ];
                }
                foreach ( $this->storagePathsChanged() as $path ) {
                        if ( $nPredicates['sha1'][$path] === false ) { // deleted
                                $deleteEntries[] = [
                                        'op' => 'delete',
                                        'path' => $path,
                                        'newSha1' => ''
                                ];
                        } else { // created/updated
                                $updateEntries[] = [
                                        'op' => $this->fileExists( $path, $oPredicates ) ? 'update' : 'create',
                                        'path' => $path,
                                        'newSha1' => $nPredicates['sha1'][$path]
                                ];
                        }
                }

                return array_merge( $nullEntries, $updateEntries, $deleteEntries );
        }

        /**
         * Check preconditions of the operation without writing anything.
         * This must update $predicates for each path that the op can change
         * except when a failing StatusValue object is returned.
         *
         * @param array $predicates
         * @return StatusValue
         */
        final public function precheck( array &$predicates ) {
                if ( $this->state !== self::STATE_NEW ) {
                        return StatusValue::newFatal( 'fileop-fail-state', self::STATE_NEW, $this->state );
                }
                $this->state = self::STATE_CHECKED;
                $status = $this->doPrecheck( $predicates );
                if ( !$status->isOK() ) {
                        $this->failed = true;
                }

                return $status;
        }

        /**
         * @param array $predicates
         * @return StatusValue
         */
        protected function doPrecheck( array &$predicates ) {
                return StatusValue::newGood();
        }

        /**
         * Attempt the operation
         *
         * @return StatusValue
         */
        final public function attempt() {
                if ( $this->state !== self::STATE_CHECKED ) {
                        return StatusValue::newFatal( 'fileop-fail-state', self::STATE_CHECKED, $this->state );
                } elseif ( $this->failed ) { // failed precheck
                        return StatusValue::newFatal( 'fileop-fail-attempt-precheck' );
                }
                $this->state = self::STATE_ATTEMPTED;
                if ( $this->doOperation ) {
                        $status = $this->doAttempt();
                        if ( !$status->isOK() ) {
                                $this->failed = true;
                                $this->logFailure( 'attempt' );
                        }
                } else { // no-op
                        $status = StatusValue::newGood();
                }

                return $status;
        }

        /**
         * @return StatusValue
         */
        protected function doAttempt() {
                return StatusValue::newGood();
        }

        /**
         * Attempt the operation in the background
         *
         * @return StatusValue
         */
        final public function attemptAsync() {
                $this->async = true;
                $result = $this->attempt();
                $this->async = false;

                return $result;
        }

        /**
         * Get the file operation parameters
         *
         * @return array (required params list, optional params list, list of params that are paths)
         */
        protected function allowedParams() {
                return [ [], [], [] ];
        }

        /**
         * Adjust params to FileBackendStore internal file calls
         *
         * @param array $params
         * @return array (required params list, optional params list)
         */
        protected function setFlags( array $params ) {
                return [ 'async' => $this->async ] + $params;
        }

        /**
         * Get a list of storage paths read from for this operation
         *
         * @return array
         */
        public function storagePathsRead() {
                return [];
        }

        /**
         * Get a list of storage paths written to for this operation
         *
         * @return array
         */
        public function storagePathsChanged() {
                return [];
        }

        /**
         * Check for errors with regards to the destination file already existing.
         * Also set the destExists, overwriteSameCase and sourceSha1 member variables.
         * A bad StatusValue will be returned if there is no chance it can be overwritten.
         *
         * @param array $predicates
         * @return StatusValue
         */
        protected function precheckDestExistence( array $predicates ) {
                $status = StatusValue::newGood();
                // Get hash of source file/string and the destination file
                $this->sourceSha1 = $this->getSourceSha1Base36(); // FS file or data string
                if ( $this->sourceSha1 === null ) { // file in storage?
                        $this->sourceSha1 = $this->fileSha1( $this->params['src'], $predicates );
                }
                $this->overwriteSameCase = false;
                $this->destExists = $this->fileExists( $this->params['dst'], $predicates );
                if ( $this->destExists ) {
                        if ( $this->getParam( 'overwrite' ) ) {
                                return $status; // OK
                        } elseif ( $this->getParam( 'overwriteSame' ) ) {
                                $dhash = $this->fileSha1( $this->params['dst'], $predicates );
                                // Check if hashes are valid and match each other...
                                if ( !strlen( $this->sourceSha1 ) || !strlen( $dhash ) ) {
                                        $status->fatal( 'backend-fail-hashes' );
                                } elseif ( $this->sourceSha1 !== $dhash ) {
                                        // Give an error if the files are not identical
                                        $status->fatal( 'backend-fail-notsame', $this->params['dst'] );
                                } else {
                                        $this->overwriteSameCase = true; // OK
                                }

                                return $status; // do nothing; either OK or bad status
                        } else {
                                $status->fatal( 'backend-fail-alreadyexists', $this->params['dst'] );

                                return $status;
                        }
                }

                return $status;
        }

        /**
         * precheckDestExistence() helper function to get the source file SHA-1.
         * Subclasses should overwride this if the source is not in storage.
         *
         * @return string|bool Returns false on failure
         */
        protected function getSourceSha1Base36() {
                return null; // N/A
        }

        /**
         * Check if a file will exist in storage when this operation is attempted
         *
         * @param string $source Storage path
         * @param array $predicates
         * @return bool
         */
        final protected function fileExists( $source, array $predicates ) {
                if ( isset( $predicates['exists'][$source] ) ) {
                        return $predicates['exists'][$source]; // previous op assures this
                } else {
                        $params = [ 'src' => $source, 'latest' => true ];

                        return $this->backend->fileExists( $params );
                }
        }

        /**
         * Get the SHA-1 of a file in storage when this operation is attempted
         *
         * @param string $source Storage path
         * @param array $predicates
         * @return string|bool False on failure
         */
        final protected function fileSha1( $source, array $predicates ) {
                if ( isset( $predicates['sha1'][$source] ) ) {
                        return $predicates['sha1'][$source]; // previous op assures this
                } elseif ( isset( $predicates['exists'][$source] ) && !$predicates['exists'][$source] ) {
                        return false; // previous op assures this
                } else {
                        $params = [ 'src' => $source, 'latest' => true ];

                        return $this->backend->getFileSha1Base36( $params );
                }
        }

        /**
         * Get the backend this operation is for
         *
         * @return FileBackendStore
         */
        public function getBackend() {
                return $this->backend;
        }

        /**
         * Log a file operation failure and preserve any temp files
         *
         * @param string $action
         */
        final public function logFailure( $action ) {
                $params = $this->params;
                $params['failedAction'] = $action;
                try {
                        $this->logger->error( get_class( $this ) .
                                " failed (batch #{$this->batchId}): " . FormatJson::encode( $params ) );
                } catch ( Exception $e ) {
                        // bad config? debug log error?
                }
        }
}