/*

 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.lang.management.ManagementFactory;

import utils.GarbageProducer;

import common.TmTool;

import utils.JstatResults;

/**

 * Base class for jstat testing which uses GarbageProducer to allocate garbage.

 */

public class GarbageProducerTest {

    // Iterations of measurement to get consistent value of counters and jstat.

    private final static int ITERATIONS = 10;

    private final static float TARGET_MEMORY_USAGE = 0.7f;

    private final static float MEASUREMENT_TOLERANCE = 0.05f;

    private final GarbageProducer garbageProducer;

    private final TmTool<? extends JstatResults> jstatTool;

    public GarbageProducerTest(TmTool<? extends JstatResults> tool) {

        garbageProducer = new GarbageProducer(TARGET_MEMORY_USAGE);

        // We will be running jstat tool

        jstatTool = tool;

    }

    public void run() throws Exception {

        // Run once and get the  results asserting that they are reasonable

        JstatResults measurement1 = jstatTool.measure();

        measurement1.assertConsistency();

        // Eat metaspace and heap then run the tool again and get the results  asserting that they are reasonable

        System.gc();

        garbageProducer.allocateMetaspaceAndHeap();

        // Collect garbage. Also update VM statistics

        System.gc();

        int i = 0;

        long collectionCountBefore = getCollectionCount();

        JstatResults measurement2 = jstatTool.measure();

        do {

            System.out.println("Measurement #" + i);

            long currentCounter = getCollectionCount();

            // Check if GC cycle occured during measurement

            if (currentCounter == collectionCountBefore) {

                measurement2.assertConsistency();

                checkOldGenMeasurement(measurement2);

                return;

            } else {

                System.out.println("GC happened during measurement.");

            }

            collectionCountBefore = getCollectionCount();

            measurement2 = jstatTool.measure();

        } while (i++ < ITERATIONS);

        // Checking will be performed without consistency guarantee.

        checkOldGenMeasurement(measurement2);

    }

    private void checkOldGenMeasurement(JstatResults measurement2) {

        float oldGenAllocationRatio = garbageProducer.getOldGenAllocationRatio() - MEASUREMENT_TOLERANCE;

        // Assert that space has been utilized accordingly

        JstatResults.assertSpaceUtilization(measurement2, TARGET_MEMORY_USAGE, oldGenAllocationRatio);

    }

    private static long getCollectionCount() {

        return ManagementFactory.getGarbageCollectorMXBeans().stream()

                .mapToLong(b -> b.getCollectionCount())

                .sum();

    }

}