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Apache Solr (module: core)
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.solr.cluster.placement.impl;
import com.google.common.annotations.VisibleForTesting;
import java.util.concurrent.Phaser;
import org.apache.solr.cluster.placement.PlacementPlugin;
import org.apache.solr.cluster.placement.PlacementPluginConfig;
import org.apache.solr.cluster.placement.PlacementPluginFactory;
/** Helper class to support dynamic reloading of plugin implementations. */
public final class DelegatingPlacementPluginFactory
implements PlacementPluginFactory {
private volatile PlacementPluginFactory delegate;
// support for tests to make sure the update is completed
private volatile Phaser phaser;
private final PlacementPluginFactory defaultPlacementPluginFactory;
/**
* Constructor.
*
* @param defaultPlacementPluginFactory A {@link PlacementPluginFactory} to use when no delegate
* is defined.
*/
public DelegatingPlacementPluginFactory(PlacementPluginFactory defaultPlacementPluginFactory) {
this.defaultPlacementPluginFactory = defaultPlacementPluginFactory;
}
@Override
public PlacementPlugin createPluginInstance() {
if (delegate != null) {
return delegate.createPluginInstance();
} else {
return defaultPlacementPluginFactory.createPluginInstance();
}
}
@Override
public PlacementPluginConfig getConfig() {
if (delegate != null) {
return delegate.getConfig();
} else {
return defaultPlacementPluginFactory.getConfig();
}
}
/**
* A phaser that will advance phases every time {@link #setDelegate(PlacementPluginFactory)} is
* called. Useful for allowing tests to know when a new delegate is finished getting set.
*/
@VisibleForTesting
public void setDelegationPhaser(Phaser phaser) {
phaser.register();
this.phaser = phaser;
}
public void setDelegate(PlacementPluginFactory delegate) {
this.delegate = delegate;
Phaser localPhaser = phaser; // volatile read
if (localPhaser != null) {
assert localPhaser.getRegisteredParties() == 1;
// we should be the only ones registered, so this will advance phase each time
localPhaser.arrive();
}
}
@VisibleForTesting
public PlacementPluginFactory getDelegate() {
return delegate;
}
}