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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.

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/*
 * 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.cassandra.tools.nodetool;

import org.apache.cassandra.tools.NodeProbe;
import org.apache.cassandra.tools.NodeTool.NodeToolCmd;

import io.airlift.airline.Command;

@Command(name = "gcstats", description = "Print GC Statistics")
public class GcStats extends NodeToolCmd
{
    @Override
    public void execute(NodeProbe probe)
    {
        double[] stats = probe.getAndResetGCStats();
        double mean = stats[2] / stats[5];
        double stdev = Math.sqrt((stats[3] / stats[5]) - (mean * mean));
        probe.output().out.printf("%20s%20s%20s%20s%20s%20s%25s%n", "Interval (ms)", "Max GC Elapsed (ms)", "Total GC Elapsed (ms)", "Stdev GC Elapsed (ms)", "GC Reclaimed (MB)", "Collections", "Direct Memory Bytes");
        probe.output().out.printf("%20.0f%20.0f%20.0f%20.0f%20.0f%20.0f%25d%n", stats[0], stats[1], stats[2], stdev, stats[4], stats[5], (long)stats[6]);
    }
}