FileOpBatch.php

Go to the documentation of this file.

<?php
class FileOpBatch {
        /* Timeout related parameters */
        const MAX_BATCH_SIZE = 1000; // integer

        public static function attempt( array $performOps, array $opts, FileJournal $journal ) {
                wfProfileIn( __METHOD__ );
                $status = Status::newGood();

                $n = count( $performOps );
                if ( $n > self::MAX_BATCH_SIZE ) {
                        $status->fatal( 'backend-fail-batchsize', $n, self::MAX_BATCH_SIZE );
                        wfProfileOut( __METHOD__ );
                        return $status;
                }

                $batchId = $journal->getTimestampedUUID();
                $allowStale = !empty( $opts['allowStale'] );
                $ignoreErrors = !empty( $opts['force'] );
                $journaled = empty( $opts['nonJournaled'] );
                $maxConcurrency = isset( $opts['concurrency'] ) ? $opts['concurrency'] : 1;

                $entries = array(); // file journal entry list
                $predicates = FileOp::newPredicates(); // account for previous ops in prechecks
                $curBatch = array(); // concurrent FileOp sub-batch accumulation
                $curBatchDeps = FileOp::newDependencies(); // paths used in FileOp sub-batch
                $pPerformOps = array(); // ordered list of concurrent FileOp sub-batches
                $lastBackend = null; // last op backend name
                // Do pre-checks for each operation; abort on failure...
                foreach ( $performOps as $index => $fileOp ) {
                        $backendName = $fileOp->getBackend()->getName();
                        $fileOp->setBatchId( $batchId ); // transaction ID
                        $fileOp->allowStaleReads( $allowStale ); // consistency level
                        // Decide if this op can be done concurrently within this sub-batch
                        // or if a new concurrent sub-batch must be started after this one...
                        if ( $fileOp->dependsOn( $curBatchDeps )
                                || count( $curBatch ) >= $maxConcurrency
                                || ( $backendName !== $lastBackend && count( $curBatch ) )
                        ) {
                                $pPerformOps[] = $curBatch; // push this batch
                                $curBatch = array(); // start a new sub-batch
                                $curBatchDeps = FileOp::newDependencies();
                        }
                        $lastBackend = $backendName;
                        $curBatch[$index] = $fileOp; // keep index
                        // Update list of affected paths in this batch
                        $curBatchDeps = $fileOp->applyDependencies( $curBatchDeps );
                        // Simulate performing the operation...
                        $oldPredicates = $predicates;
                        $subStatus = $fileOp->precheck( $predicates ); // updates $predicates
                        $status->merge( $subStatus );
                        if ( $subStatus->isOK() ) {
                                if ( $journaled ) { // journal log entries
                                        $entries = array_merge( $entries,
                                                $fileOp->getJournalEntries( $oldPredicates, $predicates ) );
                                }
                        } else { // operation failed?
                                $status->success[$index] = false;
                                ++$status->failCount;
                                if ( !$ignoreErrors ) {
                                        wfProfileOut( __METHOD__ );
                                        return $status; // abort
                                }
                        }
                }
                // Push the last sub-batch
                if ( count( $curBatch ) ) {
                        $pPerformOps[] = $curBatch;
                }

                // Log the operations in the file journal...
                if ( count( $entries ) ) {
                        $subStatus = $journal->logChangeBatch( $entries, $batchId );
                        if ( !$subStatus->isOK() ) {
                                wfProfileOut( __METHOD__ );
                                return $subStatus; // abort
                        }
                }

                if ( $ignoreErrors ) { // treat precheck() fatals as mere warnings
                        $status->setResult( true, $status->value );
                }

                // Attempt each operation (in parallel if allowed and possible)...
                self::runParallelBatches( $pPerformOps, $status );

                wfProfileOut( __METHOD__ );
                return $status;
        }

        protected static function runParallelBatches( array $pPerformOps, Status $status ) {
                $aborted = false; // set to true on unexpected errors
                foreach ( $pPerformOps as $performOpsBatch ) {
                        if ( $aborted ) { // check batch op abort flag...
                                // We can't continue (even with $ignoreErrors) as $predicates is wrong.
                                // Log the remaining ops as failed for recovery...
                                foreach ( $performOpsBatch as $i => $fileOp ) {
                                        $performOpsBatch[$i]->logFailure( 'attempt_aborted' );
                                }
                                continue;
                        }
                        $statuses = array();
                        $opHandles = array();
                        // Get the backend; all sub-batch ops belong to a single backend
                        $backend = reset( $performOpsBatch )->getBackend();
                        // Get the operation handles or actually do it if there is just one.
                        // If attemptAsync() returns a Status, it was either due to an error
                        // or the backend does not support async ops and did it synchronously.
                        foreach ( $performOpsBatch as $i => $fileOp ) {
                                if ( !$fileOp->failed() ) { // failed => already has Status
                                        // If the batch is just one operation, it's faster to avoid
                                        // pipelining as that can involve creating new TCP connections.
                                        $subStatus = ( count( $performOpsBatch ) > 1 )
                                                ? $fileOp->attemptAsync()
                                                : $fileOp->attempt();
                                        if ( $subStatus->value instanceof FileBackendStoreOpHandle ) {
                                                $opHandles[$i] = $subStatus->value; // deferred
                                        } else {
                                                $statuses[$i] = $subStatus; // done already
                                        }
                                }
                        }
                        // Try to do all the operations concurrently...
                        $statuses = $statuses + $backend->executeOpHandlesInternal( $opHandles );
                        // Marshall and merge all the responses (blocking)...
                        foreach ( $performOpsBatch as $i => $fileOp ) {
                                if ( !$fileOp->failed() ) { // failed => already has Status
                                        $subStatus = $statuses[$i];
                                        $status->merge( $subStatus );
                                        if ( $subStatus->isOK() ) {
                                                $status->success[$i] = true;
                                                ++$status->successCount;
                                        } else {
                                                $status->success[$i] = false;
                                                ++$status->failCount;
                                                $aborted = true; // set abort flag; we can't continue
                                        }
                                }
                        }
                }
                return $status;
        }
}