use EmptyBagOStuff;
use WANObjectCache;
use ArrayUtils;
-use DBError;
-use DBAccessError;
-use DBExpectedError;
-use DBUnexpectedError;
-use DBTransactionError;
-use DBTransactionSizeError;
-use DBConnectionError;
use InvalidArgumentException;
use RuntimeException;
use Exception;
$host = $this->getServerName( $i );
if ( $lag === false && !is_infinite( $maxServerLag ) ) {
$this->replLogger->error(
- "Server {host} (#$i) is not replicating?", [ 'host' => $host ] );
+ "Server {host} is not replicating?", [ 'host' => $host ] );
unset( $loads[$i] );
} elseif ( $lag > $maxServerLag ) {
$this->replLogger->warning(
- "Server {host} (#$i) has {lag} seconds of lag (>= {maxlag})",
+ "Server {host} has {lag} seconds of lag (>= {maxlag})",
[ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
);
unset( $loads[$i] );
public function getReaderIndex( $group = false, $domain = false ) {
if ( count( $this->mServers ) == 1 ) {
- # Skip the load balancing if there's only one server
+ // Skip the load balancing if there's only one server
return $this->getWriterIndex();
} elseif ( $group === false && $this->mReadIndex >= 0 ) {
- # Shortcut if generic reader exists already
+ // Shortcut if the generic reader index was already cached
return $this->mReadIndex;
}
- # Find the relevant load array
if ( $group !== false ) {
+ // Use the server weight array for this load group
if ( isset( $this->mGroupLoads[$group] ) ) {
- $nonErrorLoads = $this->mGroupLoads[$group];
+ $loads = $this->mGroupLoads[$group];
} else {
- # No loads for this group, return false and the caller can use some other group
+ // No loads for this group, return false and the caller can use some other group
$this->connLogger->info( __METHOD__ . ": no loads for group $group" );
return false;
}
} else {
- $nonErrorLoads = $this->mLoads;
+ // Use the generic load group
+ $loads = $this->mLoads;
}
- if ( !count( $nonErrorLoads ) ) {
- throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
+ // Scale the configured load ratios according to each server's load and state
+ $this->getLoadMonitor()->scaleLoads( $loads, $domain );
+
+ // Pick a server to use, accounting for weights, load, lag, and mWaitForPos
+ list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
+ if ( $i === false ) {
+ // Replica DB connection unsuccessful
+ return false;
}
- # Scale the configured load ratios according to the dynamic load if supported
- $this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $domain );
+ if ( $this->mWaitForPos && $i != $this->getWriterIndex() ) {
+ // Before any data queries are run, wait for the server to catch up to the
+ // specified position. This is used to improve session consistency. Note that
+ // when LoadBalancer::waitFor() sets mWaitForPos, the waiting triggers here,
+ // so update laggedReplicaMode as needed for consistency.
+ if ( !$this->doWait( $i ) ) {
+ $laggedReplicaMode = true;
+ }
+ }
- $laggedReplicaMode = false;
+ if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
+ // Cache the generic reader index for future ungrouped DB_REPLICA handles
+ $this->mReadIndex = $i;
+ // Record if the generic reader index is in "lagged replica DB" mode
+ if ( $laggedReplicaMode ) {
+ $this->laggedReplicaMode = true;
+ }
+ }
+
+ $serverName = $this->getServerName( $i );
+ $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
+
+ return $i;
+ }
+
+ /**
+ * @param array $loads List of server weights
+ * @param string|bool $domain
+ * @return array (reader index, lagged replica mode) or false on failure
+ */
+ private function pickReaderIndex( array $loads, $domain = false ) {
+ if ( !count( $loads ) ) {
+ throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
+ }
- # No server found yet
+ /** @var $i int|bool Index of selected server */
$i = false;
- # First try quickly looking through the available servers for a server that
- # meets our criteria
- $currentLoads = $nonErrorLoads;
+ /** @var $laggedReplicaMode bool Whether server is considered lagged */
+ $laggedReplicaMode = false;
+
+ // Quickly look through the available servers for a server that meets criteria...
+ $currentLoads = $loads;
while ( count( $currentLoads ) ) {
if ( $this->mAllowLagged || $laggedReplicaMode ) {
$i = ArrayUtils::pickRandom( $currentLoads );
} else {
$i = false;
if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
- # ChronologyProtecter causes mWaitForPos to be set via sessions.
- # This triggers doWait() after connect, so it's especially good to
- # avoid lagged servers so as to avoid just blocking in that method.
+ // ChronologyProtecter sets mWaitForPos for session consistency.
+ // This triggers doWait() after connect, so it's especially good to
+ // avoid lagged servers so as to avoid excessive delay in that method.
$ago = microtime( true ) - $this->mWaitForPos->asOfTime();
- # Aim for <= 1 second of waiting (being too picky can backfire)
+ // Aim for <= 1 second of waiting (being too picky can backfire)
$i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
}
if ( $i === false ) {
- # Any server with less lag than it's 'max lag' param is preferable
+ // Any server with less lag than it's 'max lag' param is preferable
$i = $this->getRandomNonLagged( $currentLoads, $domain );
}
if ( $i === false && count( $currentLoads ) != 0 ) {
- # All replica DBs lagged. Switch to read-only mode
+ // All replica DBs lagged. Switch to read-only mode
$this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
$i = ArrayUtils::pickRandom( $currentLoads );
$laggedReplicaMode = true;
}
if ( $i === false ) {
- # pickRandom() returned false
- # This is permanent and means the configuration or the load monitor
- # wants us to return false.
+ // pickRandom() returned false.
+ // This is permanent and means the configuration or the load monitor
+ // wants us to return false.
$this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
- return false;
+ return [ false, false ];
}
$serverName = $this->getServerName( $i );
$conn = $this->openConnection( $i, $domain );
if ( !$conn ) {
$this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
- unset( $nonErrorLoads[$i] );
- unset( $currentLoads[$i] );
+ unset( $currentLoads[$i] ); // avoid this server next iteration
$i = false;
continue;
}
$this->reuseConnection( $conn );
}
- # Return this server
+ // Return this server
break;
}
- # If all servers were down, quit now
- if ( !count( $nonErrorLoads ) ) {
+ // If all servers were down, quit now
+ if ( !count( $currentLoads ) ) {
$this->connLogger->error( "All servers down" );
}
- if ( $i !== false ) {
- # Replica DB connection successful.
- # Wait for the session master pos for a short time.
- if ( $this->mWaitForPos && $i > 0 ) {
- # When LoadBalancer::waitFor() set mWaitForPos, the wait will happen here.
- # Be sure to update laggedReplicaMode accordingly for consistency.
- if ( !$this->doWait( $i ) ) {
- $laggedReplicaMode = true;
- }
- }
- if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
- $this->mReadIndex = $i;
- # Record if the generic reader index is in "lagged replica DB" mode
- if ( $laggedReplicaMode ) {
- $this->laggedReplicaMode = true;
- }
- }
- $serverName = $this->getServerName( $i );
- $this->connLogger->debug(
- __METHOD__ . ": using server $serverName for group '$group'" );
- }
-
- return $i;
+ return [ $i, $laggedReplicaMode ];
}
public function waitFor( $pos ) {
return ( $name != '' ) ? $name : 'localhost';
}
+ /**
+ * @deprecated Since 1.30, no alternative
+ */
public function getServerInfo( $i ) {
+ wfDeprecated( __METHOD__, '1.30' );
if ( isset( $this->mServers[$i] ) ) {
return $this->mServers[$i];
} else {
}
}
+ /**
+ * @deprecated Since 1.30, construct new object
+ */
public function setServerInfo( $i, array $serverInfo ) {
+ wfDeprecated( __METHOD__, '1.30' );
$this->mServers[$i] = $serverInfo;
}
dépôts / lhc / web / wiklou.git / blobdiff