+global\LoadMonitor::getServerStates()

Complexity

Conditions	19
Paths	184

Size

Total Lines	108
Code Lines	65

Duplication

Lines	10
Ratio	9.26 %

Importance

Changes

0

<?php
	protected function getServerStates( array $serverIndexes, $domain ) {
		$writerIndex = $this->parent->getWriterIndex();
		if ( count( $serverIndexes ) == 1 && reset( $serverIndexes ) == $writerIndex ) {
			# Single server only, just return zero without caching
			return [
				'lagTimes' => [ $writerIndex => 0 ],
				'weightScales' => [ $writerIndex => 1.0 ]
			];
		}

		$key = $this->getCacheKey( $serverIndexes );
		# Randomize TTLs to reduce stampedes (4.0 - 5.0 sec)
		$ttl = mt_rand( 4e6, 5e6 ) / 1e6;
		# Keep keys around longer as fallbacks
		$staleTTL = 60;

		# (a) Check the local APC cache
		$value = $this->srvCache->get( $key );
		if ( $value && $value['timestamp'] > ( microtime( true ) - $ttl ) ) {
			$this->replLogger->debug( __METHOD__ . ": got lag times ($key) from local cache" );
			return $value; // cache hit
		}
		$staleValue = $value ?: false;

		# (b) Check the shared cache and backfill APC
		$value = $this->mainCache->get( $key );
		if ( $value && $value['timestamp'] > ( microtime( true ) - $ttl ) ) {
			$this->srvCache->set( $key, $value, $staleTTL );
			$this->replLogger->debug( __METHOD__ . ": got lag times ($key) from main cache" );

			return $value; // cache hit
		}
		$staleValue = $value ?: $staleValue;

		# (c) Cache key missing or expired; regenerate and backfill
		if ( $this->mainCache->lock( $key, 0, 10 ) ) {
			# Let this process alone update the cache value
			$cache = $this->mainCache;
			/** @noinspection PhpUnusedLocalVariableInspection */
			$unlocker = new ScopedCallback( function () use ( $cache, $key ) {

$unlocker is not used, you could remove the assignment.

The class ScopedCallback has been deprecated with message: since 1.28 use Wikimedia\ScopedCallback

				$cache->unlock( $key );
			} );
		} elseif ( $staleValue ) {
			# Could not acquire lock but an old cache exists, so use it
			return $staleValue;
		}

		$lagTimes = [];
		$weightScales = [];
		$movAveRatio = $this->movingAveRatio;
		foreach ( $serverIndexes as $i ) {
			if ( $i == $this->parent->getWriterIndex() ) {
				$lagTimes[$i] = 0; // master always has no lag
				$weightScales[$i] = 1.0; // nominal weight
				continue;
			}

			$conn = $this->parent->getAnyOpenConnection( $i );
			if ( $conn ) {
				$close = false; // already open
			} else {
				$conn = $this->parent->openConnection( $i, $domain );
				$close = true; // new connection
			}

			$lastWeight = isset( $staleValue['weightScales'][$i] )
				? $staleValue['weightScales'][$i]
				: 1.0;
			$coefficient = $this->getWeightScale( $i, $conn ?: null );

It seems like $conn ?: null can also be of type boolean; however, LoadMonitor::getWeightScale() does only seem to accept null|object<IDatabase>, maybe add an additional type check?

			$newWeight = $movAveRatio * $coefficient + ( 1 - $movAveRatio ) * $lastWeight;

			// Scale from 10% to 100% of nominal weight
			$weightScales[$i] = max( $newWeight, .10 );

			if ( !$conn ) {
				$lagTimes[$i] = false;
				$host = $this->parent->getServerName( $i );
				$this->replLogger->error( __METHOD__ . ": host $host is unreachable" );
				continue;
			}

			$lagTimes[$i] = $conn->getLag();
			if ( $lagTimes[$i] === false ) {
				$host = $this->parent->getServerName( $i );
				$this->replLogger->error( __METHOD__ . ": host $host is not replicating?" );
			}

			if ( $close ) {
				# Close the connection to avoid sleeper connections piling up.
				# Note that the caller will pick one of these DBs and reconnect,
				# which is slightly inefficient, but this only matters for the lag
				# time cache miss cache, which is far less common that cache hits.
				$this->parent->closeConnection( $conn );

It seems like $conn can also be of type boolean; however, ILoadBalancer::closeConnection() does only seem to accept object<IDatabase>, maybe add an additional type check?

			}
		}

		# Add a timestamp key so we know when it was cached
		$value = [
			'lagTimes' => $lagTimes,
			'weightScales' => $weightScales,
			'timestamp' => microtime( true )
		];
		$this->mainCache->set( $key, $value, $staleTTL );
		$this->srvCache->set( $key, $value, $staleTTL );
		$this->replLogger->info( __METHOD__ . ": re-calculated lag times ($key)" );

		return $value;
	}