MediaWiki REL1_33
QuorumLockManager.php
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1<?php
31abstract class QuorumLockManager extends LockManager {
33 protected $srvsByBucket = []; // (bucket index => (lsrv1, lsrv2, ...))
34
36 protected $degradedBuckets = []; // (bucket index => UNIX timestamp)
37
38 final protected function doLock( array $paths, $type ) {
39 return $this->doLockByType( [ $type => $paths ] );
40 }
41
42 final protected function doUnlock( array $paths, $type ) {
43 return $this->doUnlockByType( [ $type => $paths ] );
44 }
45
46 protected function doLockByType( array $pathsByType ) {
47 $status = StatusValue::newGood();
48
49 $pathsToLock = []; // (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 = []; // 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 = StatusValue::newGood();
87
88 $pathsToUnlock = []; // (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 ( $this->locksHeld[$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 ( $this->locksHeld === [] ) {
114 $status->merge( $this->releaseAllLocks() );
115 $this->degradedBuckets = []; // safe to retry the normal quorum
116 }
117
118 return $status;
119 }
120
129 final protected function doLockingRequestBucket( $bucket, array $pathsByType ) {
130 return $this->collectPledgeQuorum(
131 $bucket,
132 function ( $lockSrv ) use ( $pathsByType ) {
133 return $this->getLocksOnServer( $lockSrv, $pathsByType );
134 }
135 );
136 }
137
145 final protected function doUnlockingRequestBucket( $bucket, array $pathsByType ) {
146 return $this->releasePledges(
147 $bucket,
148 function ( $lockSrv ) use ( $pathsByType ) {
149 return $this->freeLocksOnServer( $lockSrv, $pathsByType );
150 }
151 );
152 }
153
162 final protected function collectPledgeQuorum( $bucket, callable $callback ) {
163 $status = StatusValue::newGood();
164
165 $yesVotes = 0; // locks made on trustable servers
166 $votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
167 $quorum = floor( $votesLeft / 2 + 1 ); // simple majority
168 // Get votes for each peer, in order, until we have enough...
169 foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
170 if ( !$this->isServerUp( $lockSrv ) ) {
171 --$votesLeft;
172 $status->warning( 'lockmanager-fail-svr-acquire', $lockSrv );
173 $this->degradedBuckets[$bucket] = time();
174 continue; // server down?
175 }
176 // Attempt to acquire the lock on this peer
177 $status->merge( $callback( $lockSrv ) );
178 if ( !$status->isOK() ) {
179 return $status; // vetoed; resource locked
180 }
181 ++$yesVotes; // success for this peer
182 if ( $yesVotes >= $quorum ) {
183 return $status; // lock obtained
184 }
185 --$votesLeft;
186 $votesNeeded = $quorum - $yesVotes;
187 if ( $votesNeeded > $votesLeft ) {
188 break; // short-circuit
189 }
190 }
191 // At this point, we must not have met the quorum
192 $status->setResult( false );
193
194 return $status;
195 }
196
204 final protected function releasePledges( $bucket, callable $callback ) {
205 $status = StatusValue::newGood();
206
207 $yesVotes = 0; // locks freed on trustable servers
208 $votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
209 $quorum = floor( $votesLeft / 2 + 1 ); // simple majority
210 $isDegraded = isset( $this->degradedBuckets[$bucket] ); // not the normal quorum?
211 foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
212 if ( !$this->isServerUp( $lockSrv ) ) {
213 $status->warning( 'lockmanager-fail-svr-release', $lockSrv );
214 } else {
215 // Attempt to release the lock on this peer
216 $status->merge( $callback( $lockSrv ) );
217 ++$yesVotes; // success for this peer
218 // Normally the first peers form the quorum, and the others are ignored.
219 // Ignore them in this case, but not when an alternative quorum was used.
220 if ( $yesVotes >= $quorum && !$isDegraded ) {
221 break; // lock released
222 }
223 }
224 }
225 // Set a bad StatusValue if the quorum was not met.
226 // Assumes the same "up" servers as during the acquire step.
227 $status->setResult( $yesVotes >= $quorum );
228
229 return $status;
230 }
231
239 protected function getBucketFromPath( $path ) {
240 $prefix = substr( sha1( $path ), 0, 2 ); // first 2 hex chars (8 bits)
241 return (int)base_convert( $prefix, 16, 10 ) % count( $this->srvsByBucket );
242 }
243
251 abstract protected function isServerUp( $lockSrv );
252
260 abstract protected function getLocksOnServer( $lockSrv, array $pathsByType );
261
271 abstract protected function freeLocksOnServer( $lockSrv, array $pathsByType );
272
280 abstract protected function releaseAllLocks();
281}
Apache License January AND DISTRIBUTION Definitions License shall mean the terms and conditions for use
Class for handling resource locking.
Version of LockManager that uses a quorum from peer servers for locks.
releasePledges( $bucket, callable $callback)
Attempt to release pledges with the peers for a bucket.
freeLocksOnServer( $lockSrv, array $pathsByType)
Get a connection to a lock server and release locks on $paths.
getLocksOnServer( $lockSrv, array $pathsByType)
Get a connection to a lock server and acquire locks.
doLockByType(array $pathsByType)
doLockingRequestBucket( $bucket, array $pathsByType)
Attempt to acquire locks with the peers for a bucket.
array $degradedBuckets
Map of degraded buckets.
isServerUp( $lockSrv)
Check if a lock server is up.
collectPledgeQuorum( $bucket, callable $callback)
Attempt to acquire pledges with the peers for a bucket.
doUnlockingRequestBucket( $bucket, array $pathsByType)
Attempt to release locks with the peers for a bucket.
releaseAllLocks()
Release all locks that this session is holding.
array $srvsByBucket
Map of bucket indexes to peer server lists.
doUnlock(array $paths, $type)
Unlock resources with the given keys and lock type.
doUnlockByType(array $pathsByType)
doLock(array $paths, $type)
Lock resources with the given keys and lock type.
getBucketFromPath( $path)
Get the bucket for resource path.
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Status::newGood()` to allow deletion, and then `return false` from the hook function. Ensure you consume the 'ChangeTagAfterDelete' hook to carry out custom deletion actions. $tag:name of the tag $user:user initiating the action & $status:Status object. See above. 'ChangeTagsListActive':Allows you to nominate which of the tags your extension uses are in active use. & $tags:list of all active tags. Append to this array. 'ChangeTagsAfterUpdateTags':Called after tags have been updated with the ChangeTags::updateTags function. 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Note that you also have to use ContentSecurityPolicyDefaultSource if you want non-script sources to be loaded from whatever you add. & $scriptSrc:Array of CSP directives $policyConfig:Current configuration for the CSP header $mode:ContentSecurityPolicy::REPORT_ONLY_MODE or ContentSecurityPolicy::FULL_MODE depending on type of header 'CustomEditor':When invoking the page editor Return true to allow the normal editor to be used, or false if implementing a custom editor, e.g. for a special namespace, etc. $article:Article being edited $user:User performing the edit 'DatabaseOraclePostInit':Called after initialising an Oracle database $db:the DatabaseOracle object 'DeletedContribsPager::reallyDoQuery':Called before really executing the query for Special:DeletedContributions Similar to ContribsPager::reallyDoQuery & $data:an array of results of all contribs queries $pager:The DeletedContribsPager object hooked into $offset:Index offset, inclusive $limit:Exact query limit $descending:Query direction, false for ascending, true for descending 'DeletedContributionsLineEnding':Called before a DeletedContributions HTML line is finished. 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For example, the Gadgets extension creates preferences prefixed with 'gadget-', and so anything with that prefix is excluded from the deletion. &where:An array that will be passed as the $cond parameter to IDatabase::select() to determine what will be deleted from the user_properties table. $db:The IDatabase object, useful for accessing $db->buildLike() etc. 'DifferenceEngineAfterLoadNewText':called in DifferenceEngine::loadNewText() after the new revision 's content has been loaded into the class member variable $differenceEngine->mNewContent but before returning true from this function. $differenceEngine:DifferenceEngine object 'DifferenceEngineLoadTextAfterNewContentIsLoaded':called in DifferenceEngine::loadText() after the new revision 's content has been loaded into the class member variable $differenceEngine->mNewContent but before checking if the variable 's value is null. 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For example the rcid might be set to zero due to the user being the same as the performer of the change but an extension might still want to show it under certain conditions. & $rcid:rc_id(int) of the change or 0 $differenceEngine:DifferenceEngine object $change:RecentChange object $user:User object representing the current user 'DifferenceEngineNewHeader':Allows extensions to change the $newHeader variable, which contains information about the new revision, such as the revision 's author, whether the revision was marked as a minor edit or not, etc. $differenceEngine:DifferenceEngine object & $newHeader:The string containing the various #mw-diff-otitle[1-5] divs, which include things like revision author info, revision comment, RevisionDelete link and more $formattedRevisionTools:Array containing revision tools, some of which may have been injected with the DiffRevisionTools hook $nextlink:String containing the link to the next revision(if any) $status
Definition hooks.txt:1266
injection txt This is an overview of how MediaWiki makes use of dependency injection The design described here grew from the discussion of RFC T384 The term dependency this means that anything an object needs to operate should be injected from the the object itself should only know narrow no concrete implementation of the logic it relies on The requirement to inject everything typically results in an architecture that based on two main types of and essentially stateless service objects that use other service objects to operate on the value objects As of the beginning MediaWiki is only starting to use the DI approach Much of the code still relies on global state or direct resulting in a highly cyclical dependency which acts as the top level factory for services in MediaWiki which can be used to gain access to default instances of various services MediaWikiServices however also allows new services to be defined and default services to be redefined Services are defined or redefined by providing a callback the instantiator that will return a new instance of the service When it will create an instance of MediaWikiServices and populate it with the services defined in the files listed by thereby bootstrapping the DI framework Per $wgServiceWiringFiles lists includes ServiceWiring php
Definition injection.txt:37
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