includes/filebackend/FileOpBatch.php

   1 <?php
   2 /**
   3  * Helper class for representing batch file operations.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup FileBackend
  22  * @author Aaron Schulz
  23  */
  24
  25 /**
  26  * Helper class for representing batch file operations.
  27  * Do not use this class from places outside FileBackend.
  28  *
  29  * Methods should avoid throwing exceptions at all costs.
  30  *
  31  * @ingroup FileBackend
  32  * @since 1.20
  33  */
  34 class FileOpBatch {
  35         /* Timeout related parameters */
  36         const MAX_BATCH_SIZE = 1000; // integer
  37
  38         /**
  39          * Attempt to perform a series of file operations.
  40          * Callers are responsible for handling file locking.
  41          *
  42          * $opts is an array of options, including:
  43          *   - force        : Errors that would normally cause a rollback do not.
  44          *                    The remaining operations are still attempted if any fail.
  45          *   - nonJournaled : Don't log this operation batch in the file journal.
  46          *   - concurrency  : Try to do this many operations in parallel when possible.
  47          *
  48          * The resulting Status will be "OK" unless:
  49          *   - a) unexpected operation errors occurred (network partitions, disk full...)
  50          *   - b) significant operation errors occurred and 'force' was not set
  51          *
  52          * @param array $performOps List of FileOp operations
  53          * @param array $opts Batch operation options
  54          * @param FileJournal $journal Journal to log operations to
  55          * @return Status
  56          */
  57         public static function attempt( array $performOps, array $opts, FileJournal $journal ) {
  58                 $status = Status::newGood();
  59
  60                 $n = count( $performOps );
  61                 if ( $n > self::MAX_BATCH_SIZE ) {
  62                         $status->fatal( 'backend-fail-batchsize', $n, self::MAX_BATCH_SIZE );
  63
  64                         return $status;
  65                 }
  66
  67                 $batchId = $journal->getTimestampedUUID();
  68                 $ignoreErrors = !empty( $opts['force'] );
  69                 $journaled = empty( $opts['nonJournaled'] );
  70                 $maxConcurrency = isset( $opts['concurrency'] ) ? $opts['concurrency'] : 1;
  71
  72                 $entries = array(); // file journal entry list
  73                 $predicates = FileOp::newPredicates(); // account for previous ops in prechecks
  74                 $curBatch = array(); // concurrent FileOp sub-batch accumulation
  75                 $curBatchDeps = FileOp::newDependencies(); // paths used in FileOp sub-batch
  76                 $pPerformOps = array(); // ordered list of concurrent FileOp sub-batches
  77                 $lastBackend = null; // last op backend name
  78                 // Do pre-checks for each operation; abort on failure...
  79                 foreach ( $performOps as $index => $fileOp ) {
  80                         $backendName = $fileOp->getBackend()->getName();
  81                         $fileOp->setBatchId( $batchId ); // transaction ID
  82                         // Decide if this op can be done concurrently within this sub-batch
  83                         // or if a new concurrent sub-batch must be started after this one...
  84                         if ( $fileOp->dependsOn( $curBatchDeps )
  85                                 || count( $curBatch ) >= $maxConcurrency
  86                                 || ( $backendName !== $lastBackend && count( $curBatch ) )
  87                         ) {
  88                                 $pPerformOps[] = $curBatch; // push this batch
  89                                 $curBatch = array(); // start a new sub-batch
  90                                 $curBatchDeps = FileOp::newDependencies();
  91                         }
  92                         $lastBackend = $backendName;
  93                         $curBatch[$index] = $fileOp; // keep index
  94                         // Update list of affected paths in this batch
  95                         $curBatchDeps = $fileOp->applyDependencies( $curBatchDeps );
  96                         // Simulate performing the operation...
  97                         $oldPredicates = $predicates;
  98                         $subStatus = $fileOp->precheck( $predicates ); // updates $predicates
  99                         $status->merge( $subStatus );
 100                         if ( $subStatus->isOK() ) {
 101                                 if ( $journaled ) { // journal log entries
 102                                         $entries = array_merge( $entries,
 103                                                 $fileOp->getJournalEntries( $oldPredicates, $predicates ) );
 104                                 }
 105                         } else { // operation failed?
 106                                 $status->success[$index] = false;
 107                                 ++$status->failCount;
 108                                 if ( !$ignoreErrors ) {
 109                                         return $status; // abort
 110                                 }
 111                         }
 112                 }
 113                 // Push the last sub-batch
 114                 if ( count( $curBatch ) ) {
 115                         $pPerformOps[] = $curBatch;
 116                 }
 117
 118                 // Log the operations in the file journal...
 119                 if ( count( $entries ) ) {
 120                         $subStatus = $journal->logChangeBatch( $entries, $batchId );
 121                         if ( !$subStatus->isOK() ) {
 122                                 return $subStatus; // abort
 123                         }
 124                 }
 125
 126                 if ( $ignoreErrors ) { // treat precheck() fatals as mere warnings
 127                         $status->setResult( true, $status->value );
 128                 }
 129
 130                 // Attempt each operation (in parallel if allowed and possible)...
 131                 self::runParallelBatches( $pPerformOps, $status );
 132
 133                 return $status;
 134         }
 135
 136         /**
 137          * Attempt a list of file operations sub-batches in series.
 138          *
 139          * The operations *in* each sub-batch will be done in parallel.
 140          * The caller is responsible for making sure the operations
 141          * within any given sub-batch do not depend on each other.
 142          * This will abort remaining ops on failure.
 143          *
 144          * @param array $pPerformOps Batches of file ops (batches use original indexes)
 145          * @param Status $status
 146          */
 147         protected static function runParallelBatches( array $pPerformOps, Status $status ) {
 148                 $aborted = false; // set to true on unexpected errors
 149                 foreach ( $pPerformOps as $performOpsBatch ) {
 150                         if ( $aborted ) { // check batch op abort flag...
 151                                 // We can't continue (even with $ignoreErrors) as $predicates is wrong.
 152                                 // Log the remaining ops as failed for recovery...
 153                                 foreach ( $performOpsBatch as $i => $fileOp ) {
 154                                         $status->success[$i] = false;
 155                                         ++$status->failCount;
 156                                         $performOpsBatch[$i]->logFailure( 'attempt_aborted' );
 157                                 }
 158                                 continue;
 159                         }
 160                         $statuses = array();
 161                         $opHandles = array();
 162                         // Get the backend; all sub-batch ops belong to a single backend
 163                         $backend = reset( $performOpsBatch )->getBackend();
 164                         // Get the operation handles or actually do it if there is just one.
 165                         // If attemptAsync() returns a Status, it was either due to an error
 166                         // or the backend does not support async ops and did it synchronously.
 167                         foreach ( $performOpsBatch as $i => $fileOp ) {
 168                                 if ( !isset( $status->success[$i] ) ) { // didn't already fail in precheck()
 169                                         // Parallel ops may be disabled in config due to missing dependencies,
 170                                         // (e.g. needing popen()). When they are, $performOpsBatch has size 1.
 171                                         $subStatus = ( count( $performOpsBatch ) > 1 )
 172                                                 ? $fileOp->attemptAsync()
 173                                                 : $fileOp->attempt();
 174                                         if ( $subStatus->value instanceof FileBackendStoreOpHandle ) {
 175                                                 $opHandles[$i] = $subStatus->value; // deferred
 176                                         } else {
 177                                                 $statuses[$i] = $subStatus; // done already
 178                                         }
 179                                 }
 180                         }
 181                         // Try to do all the operations concurrently...
 182                         $statuses = $statuses + $backend->executeOpHandlesInternal( $opHandles );
 183                         // Marshall and merge all the responses (blocking)...
 184                         foreach ( $performOpsBatch as $i => $fileOp ) {
 185                                 if ( !isset( $status->success[$i] ) ) { // didn't already fail in precheck()
 186                                         $subStatus = $statuses[$i];
 187                                         $status->merge( $subStatus );
 188                                         if ( $subStatus->isOK() ) {
 189                                                 $status->success[$i] = true;
 190                                                 ++$status->successCount;
 191                                         } else {
 192                                                 $status->success[$i] = false;
 193                                                 ++$status->failCount;
 194                                                 $aborted = true; // set abort flag; we can't continue
 195                                         }
 196                                 }
 197                         }
 198                 }
 199         }
 200 }