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<?php
/**
* @file
* @ingroup FileBackend
* @author Aaron Schulz
*/
/**
* Helper class for representing operations with transaction support.
* Do not use this class from places outside FileBackend.
*
* Methods called from attemptBatch() should avoid throwing exceptions at all costs.
* FileOp objects should be lightweight in order to support large arrays in memory.
*
* @ingroup FileBackend
* @since 1.19
*/
abstract class FileOp {
/** @var Array */
protected $params = array();
/** @var FileBackendStore */
protected $backend;
protected $state = self::STATE_NEW; // integer
protected $failed = false; // boolean
protected $useLatest = true; // boolean
protected $sourceSha1; // string
protected $destSameAsSource; // boolean
/* Object life-cycle */
const STATE_NEW = 1;
const STATE_CHECKED = 2;
const STATE_ATTEMPTED = 3;
/* Timeout related parameters */
const MAX_BATCH_SIZE = 1000;
const TIME_LIMIT_SEC = 300; // 5 minutes
/**
* Build a new file operation transaction
*
* @params $backend FileBackendStore
* @params $params Array
* @throws MWException
*/
final public function __construct( FileBackendStore $backend, array $params ) {
$this->backend = $backend;
list( $required, $optional ) = $this->allowedParams();
foreach ( $required as $name ) {
if ( isset( $params[$name] ) ) {
$this->params[$name] = $params[$name];
} else {
throw new MWException( "File operation missing parameter '$name'." );
}
}
foreach ( $optional as $name ) {
if ( isset( $params[$name] ) ) {
$this->params[$name] = $params[$name];
}
}
$this->params = $params;
}
/**
* Allow stale data for file reads and existence checks
*
* @return void
*/
final protected function allowStaleReads() {
$this->useLatest = false;
}
/**
* Attempt a series of file operations.
* Callers are responsible for handling file locking.
*
* $opts is an array of options, including:
* 'force' : Errors that would normally cause a rollback do not.
* The remaining operations are still attempted if any fail.
* 'allowStale' : Don't require the latest available data.
* This can increase performance for non-critical writes.
* This has no effect unless the 'force' flag is set.
*
* The resulting Status will be "OK" unless:
* a) unexpected operation errors occurred (network partitions, disk full...)
* b) significant operation errors occured and 'force' was not set
*
* @param $performOps Array List of FileOp operations
* @param $opts Array Batch operation options
* @return Status
*/
final public static function attemptBatch( array $performOps, array $opts ) {
$status = Status::newGood();
$allowStale = !empty( $opts['allowStale'] );
$ignoreErrors = !empty( $opts['force'] );
$n = count( $performOps );
if ( $n > self::MAX_BATCH_SIZE ) {
$status->fatal( 'backend-fail-batchsize', $n, self::MAX_BATCH_SIZE );
return $status;
}
$predicates = FileOp::newPredicates(); // account for previous op in prechecks
// Do pre-checks for each operation; abort on failure...
foreach ( $performOps as $index => $fileOp ) {
if ( $allowStale ) {
$fileOp->allowStaleReads(); // allow potentially stale reads
}
$subStatus = $fileOp->precheck( $predicates );
$status->merge( $subStatus );
if ( !$subStatus->isOK() ) { // operation failed?
$status->success[$index] = false;
++$status->failCount;
if ( !$ignoreErrors ) {
return $status; // abort
}
}
}
if ( $ignoreErrors ) {
# Treat all precheck() fatals as merely warnings
$status->setResult( true, $status->value );
}
// Restart PHP's execution timer and set the timeout to safe amount.
// This handles cases where the operations take a long time or where we are
// already running low on time left. The old timeout is restored afterwards.
# @TODO: re-enable this for when the number of batches is high.
#$scopedTimeLimit = new FileOpScopedPHPTimeout( self::TIME_LIMIT_SEC );
// Attempt each operation...
foreach ( $performOps as $index => $fileOp ) {
if ( $fileOp->failed() ) {
continue; // nothing to do
}
$subStatus = $fileOp->attempt();
$status->merge( $subStatus );
if ( $subStatus->isOK() ) {
$status->success[$index] = true;
++$status->successCount;
} else {
$status->success[$index] = false;
++$status->failCount;
// We can't continue (even with $ignoreErrors) as $predicates is wrong.
// Log the remaining ops as failed for recovery...
for ( $i = ($index + 1); $i < count( $performOps ); $i++ ) {
$performOps[$i]->logFailure( 'attempt_aborted' );
}
return $status; // bail out
}
}
return $status;
}
/**
* Get the value of the parameter with the given name
*
* @param $name string
* @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 array( 'exists' => array(), 'sha1' => array() );
}
/**
* Check preconditions of the operation without writing anything
*
* @param $predicates Array
* @return Status
*/
final public function precheck( array &$predicates ) {
if ( $this->state !== self::STATE_NEW ) {
return Status::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;
}
/**
* Attempt the operation, backing up files as needed; this must be reversible
*
* @return Status
*/
final public function attempt() {
if ( $this->state !== self::STATE_CHECKED ) {
return Status::newFatal( 'fileop-fail-state', self::STATE_CHECKED, $this->state );
} elseif ( $this->failed ) { // failed precheck
return Status::newFatal( 'fileop-fail-attempt-precheck' );
}
$this->state = self::STATE_ATTEMPTED;
$status = $this->doAttempt();
if ( !$status->isOK() ) {
$this->failed = true;
$this->logFailure( 'attempt' );
}
return $status;
}
/**
* Get the file operation parameters
*
* @return Array (required params list, optional params list)
*/
protected function allowedParams() {
return array( array(), array() );
}
/**
* Get a list of storage paths read from for this operation
*
* @return Array
*/
public function storagePathsRead() {
return array();
}
/**
* Get a list of storage paths written to for this operation
*
* @return Array
*/
public function storagePathsChanged() {
return array();
}
/**
* @return Status
*/
protected function doPrecheck( array &$predicates ) {
return Status::newGood();
}
/**
* @return Status
*/
protected function doAttempt() {
return Status::newGood();
}
/**
* Check for errors with regards to the destination file already existing.
* This also updates the destSameAsSource and sourceSha1 member variables.
* A bad status will be returned if there is no chance it can be overwritten.
*
* @param $predicates Array
* @return Status
*/
protected function precheckDestExistence( array $predicates ) {
$status = Status::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->destSameAsSource = false;
if ( $this->fileExists( $this->params['dst'], $predicates ) ) {
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->destSameAsSource = 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 iff the source is not in storage.
*
* @return string|false 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 $source string Storage path
* @param $predicates Array
* @return bool
*/
final protected function fileExists( $source, array $predicates ) {
if ( isset( $predicates['exists'][$source] ) ) {
return $predicates['exists'][$source]; // previous op assures this
} else {
$params = array( 'src' => $source, 'latest' => $this->useLatest );
return $this->backend->fileExists( $params );
}
}
/**
* Get the SHA-1 of a file in storage when this operation is attempted
*
* @param $source string Storage path
* @param $predicates Array
* @return string|false
*/
final protected function fileSha1( $source, array $predicates ) {
if ( isset( $predicates['sha1'][$source] ) ) {
return $predicates['sha1'][$source]; // previous op assures this
} else {
$params = array( 'src' => $source, 'latest' => $this->useLatest );
return $this->backend->getFileSha1Base36( $params );
}
}
/**
* Log a file operation failure and preserve any temp files
*
* @param $action string
* @return void
*/
final protected function logFailure( $action ) {
$params = $this->params;
$params['failedAction'] = $action;
try {
wfDebugLog( 'FileOperation',
get_class( $this ) . ' failed:' . serialize( $params ) );
} catch ( Exception $e ) {
// bad config? debug log error?
}
}
}
/**
* FileOp helper class to expand PHP execution time for a function.
* On construction, set_time_limit() is called and set to $seconds.
* When the object goes out of scope, the timer is restarted, with
* the original time limit minus the time the object existed.
*/
class FileOpScopedPHPTimeout {
protected $startTime; // float; seconds
protected $oldTimeout; // integer; seconds
protected static $stackDepth = 0; // integer
protected static $totalCalls = 0; // integer
protected static $totalElapsed = 0; // float; seconds
/* Prevent callers in infinite loops from running forever */
const MAX_TOTAL_CALLS = 1000000;
const MAX_TOTAL_TIME = 300; // seconds
/**
* @param $seconds integer
*/
public function __construct( $seconds ) {
if ( ini_get( 'max_execution_time' ) > 0 ) { // CLI uses 0
if ( self::$totalCalls >= self::MAX_TOTAL_CALLS ) {
trigger_error( "Maximum invocations of " . __CLASS__ . " exceeded." );
} elseif ( self::$totalElapsed >= self::MAX_TOTAL_TIME ) {
trigger_error( "Time limit within invocations of " . __CLASS__ . " exceeded." );
} elseif ( self::$stackDepth > 0 ) { // recursion guard
trigger_error( "Resursive invocation of " . __CLASS__ . " attempted." );
} else {
$this->oldTimeout = ini_set( 'max_execution_time', $seconds );
$this->startTime = microtime( true );
++self::$stackDepth;
++self::$totalCalls; // proof against < 1us scopes
}
}
}
/**
* Restore the original timeout.
* This does not account for the timer value on __construct().
*/
public function __destruct() {
if ( $this->oldTimeout ) {
$elapsed = microtime( true ) - $this->startTime;
// Note: a limit of 0 is treated as "forever"
set_time_limit( max( 1, $this->oldTimeout - (int)$elapsed ) );
// If each scoped timeout is for less than one second, we end up
// restoring the original timeout without any decrease in value.
// Thus web scripts in an infinite loop can run forever unless we
// take some measures to prevent this. Track total time and calls.
self::$totalElapsed += $elapsed;
--self::$stackDepth;
}
}
}
/**
* Store a file into the backend from a file on the file system.
* Parameters similar to FileBackendStore::storeInternal(), which include:
* src : source path on file system
* dst : destination storage path
* overwrite : do nothing and pass if an identical file exists at destination
* overwriteSame : override any existing file at destination
*/
class StoreFileOp extends FileOp {
protected function allowedParams() {
return array( array( 'src', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
}
protected function doPrecheck( array &$predicates ) {
$status = Status::newGood();
// Check if the source file exists on the file system
if ( !is_file( $this->params['src'] ) ) {
$status->fatal( 'backend-fail-notexists', $this->params['src'] );
return $status;
// Check if the source file is too big
} elseif ( filesize( $this->params['src'] ) > $this->backend->maxFileSizeInternal() ) {
$status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
return $status;
// Check if a file can be placed at the destination
} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
$status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
return $status;
}
// Check if destination file exists
$status->merge( $this->precheckDestExistence( $predicates ) );
if ( $status->isOK() ) {
// Update file existence predicates
$predicates['exists'][$this->params['dst']] = true;
$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
}
return $status; // safe to call attempt()
}
protected function doAttempt() {
$status = Status::newGood();
// Store the file at the destination
if ( !$this->destSameAsSource ) {
$status->merge( $this->backend->storeInternal( $this->params ) );
}
return $status;
}
protected function getSourceSha1Base36() {
wfSuppressWarnings();
$hash = sha1_file( $this->params['src'] );
wfRestoreWarnings();
if ( $hash !== false ) {
$hash = wfBaseConvert( $hash, 16, 36, 31 );
}
return $hash;
}
public function storagePathsChanged() {
return array( $this->params['dst'] );
}
}
/**
* Create a file in the backend with the given content.
* Parameters similar to FileBackendStore::createInternal(), which include:
* content : the raw file contents
* dst : destination storage path
* overwrite : do nothing and pass if an identical file exists at destination
* overwriteSame : override any existing file at destination
*/
class CreateFileOp extends FileOp {
protected function allowedParams() {
return array( array( 'content', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
}
protected function doPrecheck( array &$predicates ) {
$status = Status::newGood();
// Check if the source data is too big
if ( strlen( $this->getParam( 'content' ) ) > $this->backend->maxFileSizeInternal() ) {
$status->fatal( 'backend-fail-create', $this->params['dst'] );
return $status;
// Check if a file can be placed at the destination
} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
$status->fatal( 'backend-fail-create', $this->params['dst'] );
return $status;
}
// Check if destination file exists
$status->merge( $this->precheckDestExistence( $predicates ) );
if ( $status->isOK() ) {
// Update file existence predicates
$predicates['exists'][$this->params['dst']] = true;
$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
}
return $status; // safe to call attempt()
}
protected function doAttempt() {
$status = Status::newGood();
// Create the file at the destination
if ( !$this->destSameAsSource ) {
$status->merge( $this->backend->createInternal( $this->params ) );
}
return $status;
}
protected function getSourceSha1Base36() {
return wfBaseConvert( sha1( $this->params['content'] ), 16, 36, 31 );
}
public function storagePathsChanged() {
return array( $this->params['dst'] );
}
}
/**
* Copy a file from one storage path to another in the backend.
* Parameters similar to FileBackendStore::copyInternal(), which include:
* src : source storage path
* dst : destination storage path
* overwrite : do nothing and pass if an identical file exists at destination
* overwriteSame : override any existing file at destination
*/
class CopyFileOp extends FileOp {
protected function allowedParams() {
return array( array( 'src', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
}
protected function doPrecheck( array &$predicates ) {
$status = Status::newGood();
// Check if the source file exists
if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
$status->fatal( 'backend-fail-notexists', $this->params['src'] );
return $status;
// Check if a file can be placed at the destination
} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
$status->fatal( 'backend-fail-copy', $this->params['src'], $this->params['dst'] );
return $status;
}
// Check if destination file exists
$status->merge( $this->precheckDestExistence( $predicates ) );
if ( $status->isOK() ) {
// Update file existence predicates
$predicates['exists'][$this->params['dst']] = true;
$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
}
return $status; // safe to call attempt()
}
protected function doAttempt() {
$status = Status::newGood();
// Do nothing if the src/dst paths are the same
if ( $this->params['src'] !== $this->params['dst'] ) {
// Copy the file into the destination
if ( !$this->destSameAsSource ) {
$status->merge( $this->backend->copyInternal( $this->params ) );
}
}
return $status;
}
public function storagePathsRead() {
return array( $this->params['src'] );
}
public function storagePathsChanged() {
return array( $this->params['dst'] );
}
}
/**
* Move a file from one storage path to another in the backend.
* Parameters similar to FileBackendStore::moveInternal(), which include:
* src : source storage path
* dst : destination storage path
* overwrite : do nothing and pass if an identical file exists at destination
* overwriteSame : override any existing file at destination
*/
class MoveFileOp extends FileOp {
protected function allowedParams() {
return array( array( 'src', 'dst' ), array( 'overwrite', 'overwriteSame' ) );
}
protected function doPrecheck( array &$predicates ) {
$status = Status::newGood();
// Check if the source file exists
if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
$status->fatal( 'backend-fail-notexists', $this->params['src'] );
return $status;
// Check if a file can be placed at the destination
} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
$status->fatal( 'backend-fail-move', $this->params['src'], $this->params['dst'] );
return $status;
}
// Check if destination file exists
$status->merge( $this->precheckDestExistence( $predicates ) );
if ( $status->isOK() ) {
// Update file existence predicates
$predicates['exists'][$this->params['src']] = false;
$predicates['sha1'][$this->params['src']] = false;
$predicates['exists'][$this->params['dst']] = true;
$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
}
return $status; // safe to call attempt()
}
protected function doAttempt() {
$status = Status::newGood();
// Do nothing if the src/dst paths are the same
if ( $this->params['src'] !== $this->params['dst'] ) {
if ( !$this->destSameAsSource ) {
// Move the file into the destination
$status->merge( $this->backend->moveInternal( $this->params ) );
} else {
// Just delete source as the destination needs no changes
$params = array( 'src' => $this->params['src'] );
$status->merge( $this->backend->deleteInternal( $params ) );
}
}
return $status;
}
public function storagePathsRead() {
return array( $this->params['src'] );
}
public function storagePathsChanged() {
return array( $this->params['dst'] );
}
}
/**
* Delete a file at the given storage path from the backend.
* Parameters similar to FileBackendStore::deleteInternal(), which include:
* src : source storage path
* ignoreMissingSource : don't return an error if the file does not exist
*/
class DeleteFileOp extends FileOp {
protected function allowedParams() {
return array( array( 'src' ), array( 'ignoreMissingSource' ) );
}
protected $needsDelete = true;
protected function doPrecheck( array &$predicates ) {
$status = Status::newGood();
// Check if the source file exists
if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
if ( !$this->getParam( 'ignoreMissingSource' ) ) {
$status->fatal( 'backend-fail-notexists', $this->params['src'] );
return $status;
}
$this->needsDelete = false;
}
// Update file existence predicates
$predicates['exists'][$this->params['src']] = false;
$predicates['sha1'][$this->params['src']] = false;
return $status; // safe to call attempt()
}
protected function doAttempt() {
$status = Status::newGood();
if ( $this->needsDelete ) {
// Delete the source file
$status->merge( $this->backend->deleteInternal( $this->params ) );
}
return $status;
}
public function storagePathsChanged() {
return array( $this->params['src'] );
}
}
/**
* Placeholder operation that has no params and does nothing
*/
class NullFileOp extends FileOp {}