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diff --git a/www/wiki/extensions/SemanticMediaWiki/src/Elastic/Indexer/Rollover.php b/www/wiki/extensions/SemanticMediaWiki/src/Elastic/Indexer/Rollover.php
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+++ b/www/wiki/extensions/SemanticMediaWiki/src/Elastic/Indexer/Rollover.php
@@ -0,0 +1,170 @@
+<?php
+
+namespace SMW\Elastic\Indexer;
+
+use SMW\Elastic\Connection\Client as ElasticClient;
+use SMW\Elastic\Exception\NoConnectionException;
+
+/**
+ * The index uses V1/V2 to switch between versions during a rebuild allowing the
+ * index to be available while a reindex is on going and after the process has
+ * been indices will be switched (aka rollover) without down time. The index uses
+ * aliases to hide the "real" identity of the current active index.
+ *
+ * @see https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-rollover-index.html
+ *
+ * @license GNU GPL v2+
+ * @since 3.0
+ *
+ * @author mwjames
+ */
+class Rollover {
+
+	/**
+	 * @var ElasticClient
+	 */
+	private $connection;
+
+	/**
+	 * @since 3.0
+	 *
+	 * @param ElasticClient $connection
+	 */
+	public function __construct( ElasticClient $connection ) {
+		$this->connection = $connection;
+	}
+
+	/**
+	 * @since 3.0
+	 *
+	 * @param string $type
+	 * @param string $version
+	 *
+	 * @return string
+	 */
+	public function rollover( $type, $version ) {
+
+		$index = $this->connection->getIndexNameByType( $type );
+		$indices = $this->connection->indices();
+
+		$params = [];
+		$actions = [];
+
+		$old = $version === 'v2' ? 'v1' : 'v2';
+		$check = false;
+
+		if ( $indices->exists( [ 'index' => "$index-$old" ] ) ) {
+			$actions = [
+				[ 'remove' => [ 'index' => "$index-$old", 'alias' => $index ] ],
+				[ 'add' => [ 'index' => "$index-$version", 'alias' => $index ] ]
+			];
+
+			$check = true;
+		} else {
+			// No old index
+			$old = $version;
+
+			$actions = [
+				[ 'add' => [ 'index' => "$index-$version", 'alias' => $index ] ]
+			];
+		}
+
+		$params['body'] = [ 'actions' => $actions ];
+
+		$indices->updateAliases( $params );
+
+		if ( $check && $indices->exists( [ 'index' => "$index-$old" ] ) ) {
+			$indices->delete( [ "index" => "$index-$old" ] );
+		}
+
+		$this->connection->releaseLock( $type );
+
+		return $old;
+	}
+
+	/**
+	 * @since 3.0
+	 *
+	 * @param string $type
+	 *
+	 * @throws NoConnectionException
+	 */
+	public function update( $type ) {
+
+		// Fail hard since we expect to create an index but are unable to do so!
+		if ( !$this->connection->ping() ) {
+			throw new NoConnectionException();
+		}
+
+		$indices = $this->connection->indices();
+
+		$index = $this->connection->getIndexName(
+			$type
+		);
+
+		// Shouldn't happen but just in case where the root index is
+		// used as index but not an alias
+		if ( $indices->exists( [ 'index' => "$index" ] ) && !$indices->existsAlias( [ 'name' => "$index" ] ) ) {
+			$indices->delete(  [ 'index' => "$index" ] );
+		}
+
+		// Check v1/v2 and if both exists (which shouldn't happen but most likely
+		// caused by an unfinshed rebuilder run) then use v1 as master
+		if ( $indices->exists( [ 'index' => "$index-v1" ] ) ) {
+
+			// Just in case
+			if ( $indices->exists( [ 'index' => "$index-v2" ] ) ) {
+				$indices->delete(  [ 'index' => "$index-v2" ] );
+			}
+
+			$actions[] = [ 'add' => [ 'index' => "$index-v1", 'alias' => $index ] ];
+		} elseif ( $indices->exists( [ 'index' => "$index-v2" ] ) ) {
+			$actions[] = [ 'add' => [ 'index' => "$index-v2", 'alias' => $index ] ];
+		} else {
+			$version = $this->connection->createIndex( $type );
+
+			$actions = [
+				[ 'add' => [ 'index' => "$index-$version", 'alias' => $index ] ]
+			];
+		}
+
+		$params['body'] = [ 'actions' => $actions ];
+		$indices->updateAliases( $params );
+	}
+
+	/**
+	 * @since 3.0
+	 *
+	 * @param string $type
+	 *
+	 * @throws NoConnectionException
+	 */
+	public function delete( $type ) {
+
+		// Fail hard since we expect to delete an index but are unable to do so!
+		if ( !$this->connection->ping() ) {
+			throw new NoConnectionException();
+		}
+
+		$indices = $this->connection->indices();
+
+		$index = $this->connection->getIndexName(
+			$type
+		);
+
+		if ( $indices->exists( [ 'index' => "$index-v1" ] ) ) {
+			$indices->delete( [ 'index' => "$index-v1" ] );
+		}
+
+		if ( $indices->exists( [ 'index' => "$index-v2" ] ) ) {
+			$indices->delete( [ 'index' => "$index-v2" ] );
+		}
+
+		if ( $indices->exists( [ 'index' => "$index" ] ) && !$indices->existsAlias( [ 'name' => "$index" ] ) ) {
+			$indices->delete( [ 'index' => "$index" ] );
+		}
+
+		$this->connection->releaseLock( $type );
+	}
+
+}