org.apache.hadoop.conf.ReconfigurableBase Maven / Gradle / Ivy
/**
* 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.hadoop.conf;
import org.apache.commons.logging.*;
import java.util.Collection;
/**
* Utility base class for implementing the Reconfigurable interface.
*
* Subclasses should override reconfigurePropertyImpl to change individual
* properties and getReconfigurableProperties to get all properties that
* can be changed at run time.
*/
public abstract class ReconfigurableBase
extends Configured implements Reconfigurable {
private static final Log LOG =
LogFactory.getLog(ReconfigurableBase.class);
/**
* Construct a ReconfigurableBase.
*/
public ReconfigurableBase() {
super(new Configuration());
}
/**
* Construct a ReconfigurableBase with the {@link Configuration}
* conf.
*/
public ReconfigurableBase(Configuration conf) {
super((conf == null) ? new Configuration() : conf);
}
/**
* {@inheritDoc}
*
* This method makes the change to this objects {@link Configuration}
* and calls reconfigurePropertyImpl to update internal data structures.
* This method cannot be overridden, subclasses should instead override
* reconfigureProperty.
*/
@Override
public final String reconfigureProperty(String property, String newVal)
throws ReconfigurationException {
if (isPropertyReconfigurable(property)) {
LOG.info("changing property " + property + " to " + newVal);
String oldVal;
synchronized(getConf()) {
oldVal = getConf().get(property);
reconfigurePropertyImpl(property, newVal);
if (newVal != null) {
getConf().set(property, newVal);
} else {
getConf().unset(property);
}
}
return oldVal;
} else {
throw new ReconfigurationException(property, newVal,
getConf().get(property));
}
}
/**
* {@inheritDoc}
*
* Subclasses must override this.
*/
@Override
public abstract Collection getReconfigurableProperties();
/**
* {@inheritDoc}
*
* Subclasses may wish to override this with a more efficient implementation.
*/
@Override
public boolean isPropertyReconfigurable(String property) {
return getReconfigurableProperties().contains(property);
}
/**
* Change a configuration property.
*
* Subclasses must override this. This method applies the change to
* all internal data structures derived from the configuration property
* that is being changed. If this object owns other Reconfigurable objects
* reconfigureProperty should be called recursively to make sure that
* to make sure that the configuration of these objects is updated.
*/
protected abstract void reconfigurePropertyImpl(String property, String newVal)
throws ReconfigurationException;
}