/*
 * Copyright (C) 2015 Brett Wooldridge
 *
 * 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 com.codacy.play.tomcatcp.metrics;

import com.codacy.play.tomcatcp.utils.ClockSource;

import java.util.concurrent.atomic.AtomicLong;

/**
 * @author Brett Wooldridge
 */
public abstract class PoolStats {
    private final ClockSource clock;
    private final AtomicLong reloadAt;
    private final long timeoutMs;

    protected volatile int totalConnections;
    protected volatile int idleConnections;
    protected volatile int activeConnections;
    protected volatile int pendingThreads;

    public PoolStats(final long timeoutMs) {
        this.timeoutMs = timeoutMs;
        this.reloadAt = new AtomicLong();
        this.clock = ClockSource.INSTANCE;
    }

    public int getTotalConnections() {
        if (shouldLoad()) {
            update();
        }

        return totalConnections;
    }

    public int getIdleConnections() {
        if (shouldLoad()) {
            update();
        }

        return idleConnections;
    }

    public int getActiveConnections() {
        if (shouldLoad()) {
            update();
        }

        return activeConnections;
    }

    public int getPendingThreads() {
        if (shouldLoad()) {
            update();
        }

        return pendingThreads;
    }

    protected abstract void update();

    private boolean shouldLoad() {
        for (; ; ) {
            final long now = clock.currentTime();
            final long reloadTime = reloadAt.get();
            if (reloadTime > now) {
                return false;
            } else if (reloadAt.compareAndSet(reloadTime, clock.plusMillis(now, timeoutMs))) {
                return true;
            }
        }
    }
}

Add a class that provides updated stats of a pool
Add a class that provides updated stats of a pool
