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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.metrics;

import com.codahale.metrics.Gauge;
import com.codahale.metrics.Meter;
import com.codahale.metrics.Timer;
import org.apache.cassandra.db.commitlog.AbstractCommitLogService;
import org.apache.cassandra.db.commitlog.AbstractCommitLogSegmentManager;

import static org.apache.cassandra.metrics.CassandraMetricsRegistry.Metrics;

/**
 * Metrics for commit log
 */
public class CommitLogMetrics
{
    public static final MetricNameFactory factory = new DefaultNameFactory("CommitLog");

    /** Number of completed tasks */
    public Gauge completedTasks;
    /** Number of pending tasks */
    public Gauge pendingTasks;
    /** Current size used by all the commit log segments */
    public Gauge totalCommitLogSize;
    /** Time spent waiting for a CLS to be allocated - under normal conditions this should be zero */
    public final Timer waitingOnSegmentAllocation;
    /** The time spent waiting on CL sync; for Periodic this is only occurs when the sync is lagging its sync interval */
    public final Timer waitingOnCommit;
    /** Time spent actually flushing the contents of a buffer to disk */
    public final Timer waitingOnFlush;
    /** Number and rate of oversized mutations */
    public final Meter oversizedMutations;

    public CommitLogMetrics()
    {
        waitingOnSegmentAllocation = Metrics.timer(factory.createMetricName("WaitingOnSegmentAllocation"));
        waitingOnCommit = Metrics.timer(factory.createMetricName("WaitingOnCommit"));
        waitingOnFlush = Metrics.timer(factory.createMetricName("WaitingOnFlush"));
        oversizedMutations = Metrics.meter(factory.createMetricName("OverSizedMutations"));
    }

    public void attach(final AbstractCommitLogService service, final AbstractCommitLogSegmentManager segmentManager)
    {
        completedTasks = Metrics.register(factory.createMetricName("CompletedTasks"), new Gauge()
        {
            public Long getValue()
            {
                return service.getCompletedTasks();
            }
        });
        pendingTasks = Metrics.register(factory.createMetricName("PendingTasks"), new Gauge()
        {
            public Long getValue()
            {
                return service.getPendingTasks();
            }
        });
        totalCommitLogSize = Metrics.register(factory.createMetricName("TotalCommitLogSize"), new Gauge()
        {
            public Long getValue()
            {
                return segmentManager.onDiskSize();
            }
        });
    }
}