nullcontext.java

hadoop:Nutch集群平台

/*
 * NullContext.java
 * Copyright 2006 The Apache Software Foundation
 *
 * Licensed 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.metrics.spi;

/**
 * Null metrics context: a metrics context which does nothing.  Used as the
 * default context, so that no performance data is emitted if no configuration
 * data is found.
 * 
 */
public class NullContext extends AbstractMetricsContext {
    
    /** Creates a new instance of NullContext */
    public NullContext() {
    }
    
    /**
     * Do-nothing version of startMonitoring
     */
    public void startMonitoring() {
    }
    
    /**
     * Do-nothing version of emitRecord
     */
    protected void emitRecord(String contextName, String recordName,
                              OutputRecord outRec) 
    {}
    
    /**
     * Do-nothing version of update
     */
    protected void update(MetricsRecordImpl record) {
    }
    
    /**
     * Do-nothing version of remove
     */
    protected void remove(MetricsRecordImpl record) {
    }
}