Deprecate wfWaitForSlaves() with LBFactory::waitForReplication()
This has a cleaner interface and makes failure more explicit Change-Id: I5480845196383df85ba7538e15e507fa1b64948a
This commit is contained in:
Aaron Schulz
parent
426cadcf44
commit
fedfee628c
3 changed files with 107 additions and 36 deletions
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@ -289,6 +289,7 @@ $wgAutoloadLocalClasses = array(
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'DBMasterPos' => __DIR__ . '/includes/db/DatabaseUtility.php',
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'DBQueryError' => __DIR__ . '/includes/db/DatabaseError.php',
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'DBReadOnlyError' => __DIR__ . '/includes/db/DatabaseError.php',
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'DBReplicationWaitError' => __DIR__ . '/includes/db/loadbalancer/LBFactory.php',
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'DBSiteStore' => __DIR__ . '/includes/site/DBSiteStore.php',
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'DBTransactionError' => __DIR__ . '/includes/db/DatabaseError.php',
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'DBUnexpectedError' => __DIR__ . '/includes/db/DatabaseError.php',
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@ -3683,55 +3683,35 @@ function wfGetNull() {
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* @param string|bool $cluster Cluster name accepted by LBFactory. Default: false.
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* @param int|null $timeout Max wait time. Default: 1 day (cli), ~10 seconds (web)
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* @return bool Success (able to connect and no timeouts reached)
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* @deprecated since 1.27 Use LBFactory::waitForReplication
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*/
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function wfWaitForSlaves(
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$ifWritesSince = null, $wiki = false, $cluster = false, $timeout = null
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) {
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// B/C: first argument used to be "max seconds of lag"; ignore such values
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$ifWritesSince = ( $ifWritesSince > 1e9 ) ? $ifWritesSince : null;
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if ( $timeout === null ) {
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$timeout = ( PHP_SAPI === 'cli' ) ? 86400 : 10;
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}
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// Figure out which clusters need to be checked
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/** @var LoadBalancer[] $lbs */
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$lbs = array();
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if ( $cluster === '*' ) {
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wfGetLBFactory()->forEachLB( function ( LoadBalancer $lb ) use ( &$lbs ) {
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$lbs[] = $lb;
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} );
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} elseif ( $cluster !== false ) {
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$lbs[] = wfGetLBFactory()->getExternalLB( $cluster );
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} else {
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$lbs[] = wfGetLB( $wiki );
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$cluster = false;
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$wiki = false;
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} elseif ( $wiki === false ) {
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$wiki = wfWikiID();
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}
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// Get all the master positions of applicable DBs right now.
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// This can be faster since waiting on one cluster reduces the
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// time needed to wait on the next clusters.
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$masterPositions = array_fill( 0, count( $lbs ), false );
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foreach ( $lbs as $i => $lb ) {
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if ( $lb->getServerCount() <= 1 ) {
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// Bug 27975 - Don't try to wait for slaves if there are none
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// Prevents permission error when getting master position
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continue;
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} elseif ( $ifWritesSince && $lb->lastMasterChangeTimestamp() < $ifWritesSince ) {
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continue; // no writes since the last wait
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}
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$masterPositions[$i] = $lb->getMasterPos();
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try {
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wfGetLBFactory()->waitForReplication( array(
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'wiki' => $wiki,
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'cluster' => $cluster,
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'timeout' => $timeout,
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// B/C: first argument used to be "max seconds of lag"; ignore such values
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'ifWritesSince' => ( $ifWritesSince > 1e9 ) ? $ifWritesSince : null
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) );
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} catch ( DBReplicationWaitError $e ) {
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return false;
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}
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$ok = true;
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foreach ( $lbs as $i => $lb ) {
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if ( $masterPositions[$i] ) {
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// The DBMS may not support getMasterPos() or the whole
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// load balancer might be fake (e.g. $wgAllDBsAreLocalhost).
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$ok = $lb->waitForAll( $masterPositions[$i], $timeout ) && $ok;
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}
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}
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return $ok;
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return true;
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}
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/**
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@ -263,6 +263,90 @@ abstract class LBFactory {
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return $ret;
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}
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/**
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* Waits for the slave DBs to catch up to the current master position
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*
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* Use this when updating very large numbers of rows, as in maintenance scripts,
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* to avoid causing too much lag. Of course, this is a no-op if there are no slaves.
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*
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* By default this waits on all DB clusters actually used in this request.
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* This makes sense when lag being waiting on is caused by the code that does this check.
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* In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
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* that were not changed since the last wait check. To forcefully wait on a specific cluster
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* for a given wiki, use the 'wiki' parameter. To forcefully wait on an "external" cluster,
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* use the "cluster" parameter.
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*
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* Never call this function after a large DB write that is *still* in a transaction.
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* It only makes sense to call this after the possible lag inducing changes were committed.
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*
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* @param array $opts Optional fields that include:
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* - wiki : wait on the load balancer DBs that handles the given wiki
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* - cluster : wait on the given external load balancer DBs
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* - timeout : Max wait time. Default: ~60 seconds
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* - ifWritesSince: Only wait if writes were done since this UNIX timestamp
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* @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
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* @since 1.27
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*/
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public function waitForReplication( array $opts = array() ) {
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$opts += array(
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'wiki' => false,
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'cluster' => false,
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'timeout' => 60,
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'ifWritesSince' => null
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);
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// Figure out which clusters need to be checked
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/** @var LoadBalancer[] $lbs */
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$lbs = array();
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if ( $opts['cluster'] !== false ) {
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$lbs[] = $this->getExternalLB( $opts['cluster'] );
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} elseif ( $opts['wiki'] !== false ) {
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$lbs[] = $this->getMainLB( $opts['wiki'] );
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} else {
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$this->forEachLB( function ( LoadBalancer $lb ) use ( &$lbs ) {
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$lbs[] = $lb;
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} );
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if ( !$lbs ) {
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return; // nothing actually used
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}
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}
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// Get all the master positions of applicable DBs right now.
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// This can be faster since waiting on one cluster reduces the
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// time needed to wait on the next clusters.
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$masterPositions = array_fill( 0, count( $lbs ), false );
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foreach ( $lbs as $i => $lb ) {
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if ( $lb->getServerCount() <= 1 ) {
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// Bug 27975 - Don't try to wait for slaves if there are none
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// Prevents permission error when getting master position
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continue;
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} elseif ( $opts['ifWritesSince']
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&& $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
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) {
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continue; // no writes since the last wait
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}
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$masterPositions[$i] = $lb->getMasterPos();
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}
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$failed = array();
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foreach ( $lbs as $i => $lb ) {
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if ( $masterPositions[$i] ) {
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// The DBMS may not support getMasterPos() or the whole
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// load balancer might be fake (e.g. $wgAllDBsAreLocalhost).
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if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
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$failed[] = $lb->getServerName( $lb->getWriterIndex() );
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}
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}
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}
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if ( $failed ) {
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throw new DBReplicationWaitError(
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"Could not wait for slaves to catch up to " .
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implode( ', ', $failed )
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);
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}
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}
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/**
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* Disable the ChronologyProtector for all load balancers
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*
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@ -329,3 +413,9 @@ class DBAccessError extends MWException {
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"This is not allowed." );
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}
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}
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/**
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* Exception class for replica DB wait timeouts
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*/
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class DBReplicationWaitError extends Exception {
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}
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