MediaWiki  1.23.8
QuorumLockManager.php
Go to the documentation of this file.
1 <?php
31 abstract class QuorumLockManager extends LockManager {
33  protected $srvsByBucket = array(); // (bucket index => (lsrv1, lsrv2, ...))
34 
36  protected $degradedBuckets = array(); // (buckey index => UNIX timestamp)
37 
38  final protected function doLock( array $paths, $type ) {
39  return $this->doLockByType( array( $type => $paths ) );
40  }
41 
42  final protected function doUnlock( array $paths, $type ) {
43  return $this->doUnlockByType( array( $type => $paths ) );
44  }
45 
46  protected function doLockByType( array $pathsByType ) {
47  $status = Status::newGood();
48 
49  $pathsToLock = array(); // (bucket => type => paths)
50  // Get locks that need to be acquired (buckets => locks)...
51  foreach ( $pathsByType as $type => $paths ) {
52  foreach ( $paths as $path ) {
53  if ( isset( $this->locksHeld[$path][$type] ) ) {
54  ++$this->locksHeld[$path][$type];
55  } else {
56  $bucket = $this->getBucketFromPath( $path );
57  $pathsToLock[$bucket][$type][] = $path;
58  }
59  }
60  }
61 
62  $lockedPaths = array(); // files locked in this attempt (type => paths)
63  // Attempt to acquire these locks...
64  foreach ( $pathsToLock as $bucket => $pathsToLockByType ) {
65  // Try to acquire the locks for this bucket
66  $status->merge( $this->doLockingRequestBucket( $bucket, $pathsToLockByType ) );
67  if ( !$status->isOK() ) {
68  $status->merge( $this->doUnlockByType( $lockedPaths ) );
69 
70  return $status;
71  }
72  // Record these locks as active
73  foreach ( $pathsToLockByType as $type => $paths ) {
74  foreach ( $paths as $path ) {
75  $this->locksHeld[$path][$type] = 1; // locked
76  // Keep track of what locks were made in this attempt
77  $lockedPaths[$type][] = $path;
78  }
79  }
80  }
81 
82  return $status;
83  }
84 
85  protected function doUnlockByType( array $pathsByType ) {
86  $status = Status::newGood();
87 
88  $pathsToUnlock = array(); // (bucket => type => paths)
89  foreach ( $pathsByType as $type => $paths ) {
90  foreach ( $paths as $path ) {
91  if ( !isset( $this->locksHeld[$path][$type] ) ) {
92  $status->warning( 'lockmanager-notlocked', $path );
93  } else {
94  --$this->locksHeld[$path][$type];
95  // Reference count the locks held and release locks when zero
96  if ( $this->locksHeld[$path][$type] <= 0 ) {
97  unset( $this->locksHeld[$path][$type] );
98  $bucket = $this->getBucketFromPath( $path );
99  $pathsToUnlock[$bucket][$type][] = $path;
100  }
101  if ( !count( $this->locksHeld[$path] ) ) {
102  unset( $this->locksHeld[$path] ); // no SH or EX locks left for key
103  }
104  }
105  }
106  }
107 
108  // Remove these specific locks if possible, or at least release
109  // all locks once this process is currently not holding any locks.
110  foreach ( $pathsToUnlock as $bucket => $pathsToUnlockByType ) {
111  $status->merge( $this->doUnlockingRequestBucket( $bucket, $pathsToUnlockByType ) );
112  }
113  if ( !count( $this->locksHeld ) ) {
114  $status->merge( $this->releaseAllLocks() );
115  $this->degradedBuckets = array(); // safe to retry the normal quorum
116  }
117 
118  return $status;
119  }
120 
129  final protected function doLockingRequestBucket( $bucket, array $pathsByType ) {
130  $status = Status::newGood();
131 
132  $yesVotes = 0; // locks made on trustable servers
133  $votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
134  $quorum = floor( $votesLeft / 2 + 1 ); // simple majority
135  // Get votes for each peer, in order, until we have enough...
136  foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
137  if ( !$this->isServerUp( $lockSrv ) ) {
138  --$votesLeft;
139  $status->warning( 'lockmanager-fail-svr-acquire', $lockSrv );
140  $this->degradedBuckets[$bucket] = time();
141  continue; // server down?
142  }
143  // Attempt to acquire the lock on this peer
144  $status->merge( $this->getLocksOnServer( $lockSrv, $pathsByType ) );
145  if ( !$status->isOK() ) {
146  return $status; // vetoed; resource locked
147  }
148  ++$yesVotes; // success for this peer
149  if ( $yesVotes >= $quorum ) {
150  return $status; // lock obtained
151  }
152  --$votesLeft;
153  $votesNeeded = $quorum - $yesVotes;
154  if ( $votesNeeded > $votesLeft ) {
155  break; // short-circuit
156  }
157  }
158  // At this point, we must not have met the quorum
159  $status->setResult( false );
160 
161  return $status;
162  }
163 
171  final protected function doUnlockingRequestBucket( $bucket, array $pathsByType ) {
172  $status = Status::newGood();
173 
174  $yesVotes = 0; // locks freed on trustable servers
175  $votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
176  $quorum = floor( $votesLeft / 2 + 1 ); // simple majority
177  $isDegraded = isset( $this->degradedBuckets[$bucket] ); // not the normal quorum?
178  foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
179  if ( !$this->isServerUp( $lockSrv ) ) {
180  $status->warning( 'lockmanager-fail-svr-release', $lockSrv );
181  } else {
182  // Attempt to release the lock on this peer
183  $status->merge( $this->freeLocksOnServer( $lockSrv, $pathsByType ) );
184  ++$yesVotes; // success for this peer
185  // Normally the first peers form the quorum, and the others are ignored.
186  // Ignore them in this case, but not when an alternative quorum was used.
187  if ( $yesVotes >= $quorum && !$isDegraded ) {
188  break; // lock released
189  }
190  }
191  }
192  // Set a bad status if the quorum was not met.
193  // Assumes the same "up" servers as during the acquire step.
194  $status->setResult( $yesVotes >= $quorum );
195 
196  return $status;
197  }
198 
206  protected function getBucketFromPath( $path ) {
207  $prefix = substr( sha1( $path ), 0, 2 ); // first 2 hex chars (8 bits)
208  return (int)base_convert( $prefix, 16, 10 ) % count( $this->srvsByBucket );
209  }
210 
218  abstract protected function isServerUp( $lockSrv );
219 
227  abstract protected function getLocksOnServer( $lockSrv, array $pathsByType );
228 
238  abstract protected function freeLocksOnServer( $lockSrv, array $pathsByType );
239 
247  abstract protected function releaseAllLocks();
248 }
LockManager
Class for handling resource locking.
Definition: LockManager.php:45
QuorumLockManager\doUnlockByType
doUnlockByType(array $pathsByType)
Definition: QuorumLockManager.php:83
QuorumLockManager\getBucketFromPath
getBucketFromPath( $path)
Get the bucket for resource path.
Definition: QuorumLockManager.php:204
QuorumLockManager\$degradedBuckets
array $degradedBuckets
Map of degraded buckets *.
Definition: QuorumLockManager.php:34
php
skin txt MediaWiki includes four core it has been set as the default in MediaWiki since the replacing Monobook it had been been the default skin since before being replaced by Vector largely rewritten in while keeping its appearance Several legacy skins were removed in the as the burden of supporting them became too heavy to bear Those in etc for skin dependent CSS etc for skin dependent JavaScript These can also be customised on a per user by etc This feature has led to a wide variety of user styles becoming that gallery is a good place to ending in php
Definition: skin.txt:62
QuorumLockManager\doLockingRequestBucket
doLockingRequestBucket( $bucket, array $pathsByType)
Attempt to acquire locks with the peers for a bucket.
Definition: QuorumLockManager.php:127
Status\newGood
static newGood( $value=null)
Factory function for good results.
Definition: Status.php:77
QuorumLockManager
Version of LockManager that uses a quorum from peer servers for locks.
Definition: QuorumLockManager.php:31
QuorumLockManager\releaseAllLocks
releaseAllLocks()
Release all locks that this session is holding.
QuorumLockManager\isServerUp
isServerUp( $lockSrv)
Check if a lock server is up.
QuorumLockManager\doLockByType
doLockByType(array $pathsByType)
Definition: QuorumLockManager.php:44
array
the array() calling protocol came about after MediaWiki 1.4rc1.
List of Api Query prop modules.
QuorumLockManager\doUnlockingRequestBucket
doUnlockingRequestBucket( $bucket, array $pathsByType)
Attempt to release locks with the peers for a bucket.
Definition: QuorumLockManager.php:169
QuorumLockManager\doUnlock
doUnlock(array $paths, $type)
Unlock resources with the given keys and lock type.
Definition: QuorumLockManager.php:40
QuorumLockManager\$srvsByBucket
array $srvsByBucket
Map of bucket indexes to peer server lists *.
Definition: QuorumLockManager.php:32
$path
$path
Definition: NoLocalSettings.php:35
as
This document is intended to provide useful advice for parties seeking to redistribute MediaWiki to end users It s targeted particularly at maintainers for Linux since it s been observed that distribution packages of MediaWiki often break We ve consistently had to recommend that users seeking support use official tarballs instead of their distribution s and this often solves whatever problem the user is having It would be nice if this could such as
Definition: distributors.txt:9
QuorumLockManager\freeLocksOnServer
freeLocksOnServer( $lockSrv, array $pathsByType)
Get a connection to a lock server and release locks on $paths.
QuorumLockManager\doLock
doLock(array $paths, $type)
Lock resources with the given keys and lock type.
Definition: QuorumLockManager.php:36
QuorumLockManager\getLocksOnServer
getLocksOnServer( $lockSrv, array $pathsByType)
Get a connection to a lock server and acquire locks.
$type
$type
Definition: testCompression.php:46