cassandra-trunk/test/unit/org/apache/cassandra/utils/UUIDTest.java
package org.apache.cassandra.utils;
/*
 *
 * 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.
 *
 */


import java.nio.ByteBuffer;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

import org.junit.Assert;
import org.junit.Test;

import com.google.common.collect.Sets;

import org.apache.cassandra.db.marshal.TimeUUIDType;
import org.cliffc.high_scale_lib.NonBlockingHashMap;

import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static org.apache.cassandra.utils.TimeUUID.Generator.nextTimeUUID;
import static org.apache.cassandra.utils.TimeUUID.Generator.nextTimeUUIDAsBytes;


public class UUIDTest
{
    @Test
    public void verifyType1()
    {

        UUID uuid = nextTimeUUID().asUUID();
        assert uuid.version() == 1;
    }

    @Test
    public void verifyOrdering1()
    {
        UUID one = nextTimeUUID().asUUID();
        UUID two = nextTimeUUID().asUUID();
        assert one.timestamp() < two.timestamp();
    }

    @Test
    public void testDecomposeAndRaw()
    {
        UUID a = nextTimeUUID().asUUID();
        byte[] decomposed = UUIDGen.decompose(a);
        UUID b = UUIDGen.getUUID(ByteBuffer.wrap(decomposed));
        assert a.equals(b);
    }

    @Test
    public void testToFromByteBuffer()
    {
        UUID a = nextTimeUUID().asUUID();
        ByteBuffer bb = UUIDGen.toByteBuffer(a);
        UUID b = UUIDGen.getUUID(bb);
        assert a.equals(b);
    }

    @Test
    public void testTimeUUIDType()
    {
        TimeUUIDType comp = TimeUUIDType.instance;
        ByteBuffer first = ByteBuffer.wrap(nextTimeUUIDAsBytes());
        ByteBuffer second = ByteBuffer.wrap(nextTimeUUIDAsBytes());
        assert comp.compare(first, second) < 0;
        assert comp.compare(second, first) > 0;
        ByteBuffer sameAsFirst = ByteBuffer.wrap(UUIDGen.decompose(UUIDGen.getUUID(first)));
        assert comp.compare(first, sameAsFirst) == 0;
    }

    @Test
    public void testUUIDTimestamp()
    {
        long now = System.currentTimeMillis();
        TimeUUID uuid = nextTimeUUID();
        long tstamp = uuid.unix(MILLISECONDS);

        // I'll be damn is the uuid timestamp is more than 10ms after now
        assert now <= tstamp && now >= tstamp - 10 : "now = " + now + ", timestamp = " + tstamp;
    }

    /*
     * Don't ignore spurious failures of this test since it is testing concurrent access
     * and might not fail reliably.
     */
    @Test
    public void verifyConcurrentUUIDGeneration() throws Throwable
    {
        long iterations = 250000;
        int threads = 4;
        ExecutorService es = Executors.newFixedThreadPool(threads);
        try
        {
            AtomicBoolean failedOrdering = new AtomicBoolean(false);
            AtomicBoolean failedDuplicate = new AtomicBoolean(false);
            Set<UUID> generated = Sets.newSetFromMap(new NonBlockingHashMap<>());
            Runnable task = () -> {
                long lastTimestamp = 0;
                long newTimestamp = 0;

                for (long i = 0; i < iterations; i++)
                {
                    UUID uuid = nextTimeUUID().asUUID();
                    newTimestamp = uuid.timestamp();

                    if (lastTimestamp >= newTimestamp)
                        failedOrdering.set(true);
                    if (!generated.add(uuid))
                        failedDuplicate.set(true);

                    lastTimestamp = newTimestamp;
                }
            };

            for (int i = 0; i < threads; i++)
            {
                es.execute(task);
            }
            es.shutdown();
            Assert.assertTrue(es.awaitTermination(1, TimeUnit.MINUTES));

            assert !failedOrdering.get();
            assert !failedDuplicate.get();
        }
        finally
        {
            es.shutdown();
        }
    }
}
