| /* |
| * 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.distributed.test; |
| |
| import java.io.IOException; |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.List; |
| import java.util.Random; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.atomic.AtomicBoolean; |
| import java.util.concurrent.atomic.AtomicInteger; |
| import java.util.function.BooleanSupplier; |
| |
| import com.google.common.util.concurrent.Uninterruptibles; |
| import org.junit.Assert; |
| import org.junit.Test; |
| |
| import org.apache.cassandra.distributed.Cluster; |
| import org.apache.cassandra.distributed.api.ConsistencyLevel; |
| |
| /** |
| * A simple sanity check that uses CAS as mutex: each lock tries to CAS a variable thread_id for a specific row, |
| * and set its own thread id. Then it sleeps for a short time, and releases the lock. |
| * |
| * Write timeouts are handled by simply re-reading the variable and checking if locking has actually succeeded. |
| */ |
| public class CasCriticalSectionTest extends TestBaseImpl |
| { |
| private static Random rng = new Random(); |
| private static final int threadCount = 5; |
| private static final int rowCount = 1; |
| |
| @Test |
| public void criticalSectionTest() throws IOException, InterruptedException |
| { |
| try (Cluster cluster = init(Cluster.create(5, c -> c.set("paxos_variant", "v2") |
| .set("write_request_timeout_in_ms", 2000L) |
| .set("cas_contention_timeout_in_ms", 2000L) |
| .set("request_timeout_in_ms", 2000L)))) |
| { |
| cluster.schemaChange("create table " + KEYSPACE + ".tbl (pk int, ck int, thread_id int, PRIMARY KEY(pk, ck))"); |
| |
| List<Thread> threads = new ArrayList<>(); |
| |
| AtomicBoolean failed = new AtomicBoolean(false); |
| AtomicBoolean stop = new AtomicBoolean(false); |
| BooleanSupplier exitCondition = () -> failed.get() || stop.get(); |
| |
| for (int i = 0; i < rowCount; i++) |
| { |
| final int rowId = i; |
| AtomicInteger counter = new AtomicInteger(); |
| cluster.coordinator(1) |
| .execute("insert into " + KEYSPACE + ".tbl (pk, ck, thread_id) VALUES (?, ?, ?) IF NOT EXISTS", |
| ConsistencyLevel.QUORUM, |
| 1, rowId, 0); |
| |
| // threads should be numbered from 1 to allow 0 to be "unlocked" |
| for (int j = 1; j <= threadCount; j++) |
| { |
| int threadId = j; |
| AtomicInteger lockedTimes = new AtomicInteger(); |
| AtomicInteger unlockedTimes = new AtomicInteger(); |
| |
| Runnable sanityCheck = () -> { |
| Assert.assertEquals(lockedTimes.get(), unlockedTimes.get()); |
| }; |
| threads.add(new Thread(() -> { |
| while (!exitCondition.getAsBoolean()) |
| { |
| while (!tryLockOnce(cluster, threadId, rowId)) |
| { |
| if (exitCondition.getAsBoolean()) |
| { |
| sanityCheck.run(); |
| return; |
| } |
| } |
| int ctr = counter.getAndIncrement(); |
| if (ctr != 0) |
| { |
| failed.set(true); |
| Assert.fail(String.format("Thread %s encountered lock that is held by %d participants while trying to lock.", |
| Thread.currentThread().getName(), |
| ctr)); |
| } |
| |
| // hold lock for a bit |
| Uninterruptibles.sleepUninterruptibly(rng.nextInt(5), TimeUnit.MILLISECONDS); |
| ctr = counter.decrementAndGet(); |
| if (ctr != 0) |
| { |
| failed.set(true); |
| Assert.fail(String.format("Thread %s encountered lock that is held by %d participants while trying to unlock.", |
| Thread.currentThread().getName(), |
| ctr)); |
| } |
| while (!tryUnlockOnce(cluster, threadId, rowId)) |
| { |
| if (exitCondition.getAsBoolean()) |
| { |
| sanityCheck.run(); |
| return; |
| } |
| } |
| } |
| sanityCheck.run(); |
| }, String.format("CAS Thread %d-%d", rowId, threadId))); |
| } |
| } |
| |
| for (Thread thread : threads) |
| thread.start(); |
| |
| Thread.sleep(TimeUnit.SECONDS.toMillis(30)); |
| stop.set(true); |
| |
| for (Thread thread : threads) |
| thread.join(); |
| |
| Assert.assertFalse(failed.get()); |
| } |
| } |
| |
| public static boolean isCasSuccess(Object[][] res) |
| { |
| if (res == null || res.length != 1) |
| return false; |
| |
| return Arrays.equals(res[0], new Object[] {true}); |
| } |
| |
| public static boolean tryLockOnce(Cluster cluster, int threadId, int rowId) |
| { |
| Object[][] res = null; |
| |
| try |
| { |
| res = cluster.coordinator(rng.nextInt(cluster.size()) + 1) |
| .execute("update " + KEYSPACE + ".tbl SET thread_id = ? WHERE pk = ? AND ck = ? IF thread_id = 0", |
| ConsistencyLevel.QUORUM, |
| threadId, 1, rowId); |
| return isCasSuccess(res); |
| } |
| catch (Throwable writeTimeout) |
| { |
| while (true) |
| { |
| try |
| { |
| res = cluster.coordinator(rng.nextInt(cluster.size()) + 1) |
| .execute("SELECT thread_id FROM " + KEYSPACE + ".tbl WHERE pk = ? AND ck = ?", |
| ConsistencyLevel.SERIAL, |
| 1, rowId); |
| break; |
| } |
| catch (Throwable t) |
| { |
| // retry |
| } |
| } |
| |
| return (int) res[0][0] == threadId; |
| } |
| } |
| |
| public static boolean tryUnlockOnce(Cluster cluster, int threadId, int rowId) |
| { |
| Object[][] res = null; |
| |
| try |
| { |
| res = cluster.coordinator(rng.nextInt(cluster.size()) + 1) |
| .execute("update " + KEYSPACE + ".tbl SET thread_id = ? WHERE pk = ? AND ck = ? IF thread_id = ?", |
| ConsistencyLevel.QUORUM, |
| 0, 1, rowId, threadId); |
| return isCasSuccess(res); |
| } |
| catch (Throwable writeTimeout) |
| { |
| while (true) |
| { |
| try |
| { |
| res = cluster.coordinator(rng.nextInt(cluster.size()) + 1) |
| .execute("SELECT thread_id FROM " + KEYSPACE + ".tbl WHERE pk = ? AND ck = ?", |
| ConsistencyLevel.SERIAL, |
| 1, rowId); |
| break; |
| } |
| catch (Throwable t) |
| { |
| // retry |
| } |
| } |
| |
| return (int) res[0][0] != threadId; |
| } |
| } |
| |
| } |