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Fix another deadlock which can occur while acquiring merge buffers #16372
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227 changes: 227 additions & 0 deletions
227
...ing/src/test/java/org/apache/druid/query/groupby/GroupByResourcesReservationPoolTest.java
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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. | ||
*/ | ||
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package org.apache.druid.query.groupby; | ||
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import com.google.common.collect.ImmutableList; | ||
import com.google.common.collect.ImmutableMap; | ||
import org.apache.druid.collections.BlockingPool; | ||
import org.apache.druid.collections.DefaultBlockingPool; | ||
import org.apache.druid.error.DruidException; | ||
import org.apache.druid.java.util.common.Intervals; | ||
import org.apache.druid.java.util.common.concurrent.Execs; | ||
import org.apache.druid.java.util.common.granularity.Granularities; | ||
import org.apache.druid.query.QueryResourceId; | ||
import org.apache.druid.query.dimension.DefaultDimensionSpec; | ||
import org.junit.Assert; | ||
import org.junit.Ignore; | ||
import org.junit.Test; | ||
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import java.nio.ByteBuffer; | ||
import java.util.concurrent.CountDownLatch; | ||
import java.util.concurrent.ExecutorService; | ||
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public class GroupByResourcesReservationPoolTest | ||
{ | ||
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/** | ||
* CONFIG + QUERY require exactly 1 merge buffer to succeed if 'willMergeRunners' is true while allocating the resources | ||
*/ | ||
private static final GroupByQueryConfig CONFIG = new GroupByQueryConfig(); | ||
private static final GroupByQuery QUERY = GroupByQuery.builder() | ||
.setInterval(Intervals.ETERNITY) | ||
.setDataSource("foo") | ||
.setDimensions( | ||
ImmutableList.of( | ||
new DefaultDimensionSpec("dim2", "_d0") | ||
) | ||
) | ||
.setGranularity(Granularities.ALL) | ||
.setContext( | ||
ImmutableMap.of("timeout", 0) | ||
) // Query can block indefinitely | ||
.build(); | ||
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/** | ||
* This test confirms that the interleaved GroupByResourcesReservationPool.reserve() and GroupByResourcesReservationPool.clean() | ||
* between multiple threads succeed. It is specifically designed to test the case when the operations are interleaved in the | ||
* following manner: | ||
* <p> | ||
* THREAD1 THREAD2 | ||
* pool.reserve(query1) | ||
* pool.reserve(query2) | ||
* pool.clean(query1) | ||
* <p> | ||
* This test assumes a few things about the implementation of the interfaces, which are laid out in the comments. | ||
* <p> | ||
* The test should complete under 10 seconds, and the majority of the time would be consumed by waiting for the thread | ||
* that sleeps for 5 seconds | ||
*/ | ||
@Ignore( | ||
"Isn't run as a part of CI since it sleeps for 5 seconds. Callers must run the test manually if any changes are made " | ||
+ "to the corresponding class" | ||
) | ||
@Test(timeout = 100_000L) | ||
public void testInterleavedReserveAndRemove() | ||
{ | ||
ExecutorService executor = Execs.multiThreaded(3, "group-by-resources-reservation-pool-test-%d"); | ||
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// Sanity checks that the query will acquire exactly one merge buffer. This safeguards the test being useful in | ||
// case the merge buffer acquisition code changes to acquire less than one merge buffer (the test would be | ||
// useless in that case) or more than one merge buffer (the test would incorrectly fail in that case) | ||
Assert.assertEquals( | ||
1, | ||
GroupByQueryResources.countRequiredMergeBufferNumForMergingQueryRunner(CONFIG, QUERY) | ||
+ GroupByQueryResources.countRequiredMergeBufferNumForToolchestMerge(QUERY) | ||
); | ||
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// Blocking pool with a single buffer, which means only one of the queries can succeed at a time | ||
BlockingPool<ByteBuffer> mergeBufferPool = new DefaultBlockingPool<>(() -> ByteBuffer.allocate(100), 1); | ||
GroupByResourcesReservationPool groupByResourcesReservationPool = | ||
new GroupByResourcesReservationPool(mergeBufferPool, CONFIG); | ||
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// Latch indicating that the first thread has called reservationPool.reserve() | ||
CountDownLatch reserveCalledByFirstThread = new CountDownLatch(1); | ||
// Latch indicating that the second thread has called reservationPool.reserve() | ||
CountDownLatch reserveCalledBySecondThread = new CountDownLatch(1); | ||
// Latch indicating that all the threads have been completed successfully. Main thread waits on this latch before exiting | ||
CountDownLatch threadsCompleted = new CountDownLatch(2); | ||
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// THREAD 1 | ||
executor.submit(() -> { | ||
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QueryResourceId queryResourceId1 = new QueryResourceId("test-id-1") | ||
{ | ||
@Override | ||
public int hashCode() | ||
{ | ||
// IMPORTANT ASSUMPTION: For the test to be useful, it assumes that under the hood we are using a | ||
// ConcurrentHashMap<QueryResourceId, GroupByResources> (or a concurrent map with similar implementation) that | ||
// implements granular locking of the nodes | ||
// The hashCode of the queryResourceId used in Thread1 and Thread2 is the same. Therefore, both the queryIds | ||
// would be guarded by the same lock | ||
return 10; | ||
} | ||
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@Override | ||
public boolean equals(Object o) | ||
{ | ||
return super.equals(o); | ||
} | ||
}; | ||
groupByResourcesReservationPool.reserve(queryResourceId1, QUERY, true); | ||
reserveCalledByFirstThread.countDown(); | ||
try { | ||
reserveCalledBySecondThread.await(); | ||
} | ||
catch (InterruptedException e) { | ||
Assert.fail("Interrupted while waiting for second reserve call to be made"); | ||
} | ||
groupByResourcesReservationPool.clean(queryResourceId1); | ||
threadsCompleted.countDown(); | ||
}); | ||
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// THREAD 2 | ||
executor.submit(() -> { | ||
try { | ||
reserveCalledByFirstThread.await(); | ||
} | ||
catch (InterruptedException e) { | ||
Assert.fail("Interrupted while waiting for first reserve call to be made"); | ||
} | ||
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QueryResourceId queryResourceId2 = new QueryResourceId("test-id-2") | ||
{ | ||
@Override | ||
public int hashCode() | ||
{ | ||
return 10; | ||
} | ||
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@Override | ||
public boolean equals(Object o) | ||
{ | ||
return super.equals(o); | ||
} | ||
}; | ||
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// Since the reserve() call is blocking, we need to execute it separately, so that we can count down the latch | ||
// and inform Thread1 the reserve call has been made by this thread | ||
executor.submit(() -> { | ||
groupByResourcesReservationPool.reserve(queryResourceId2, QUERY, true); | ||
threadsCompleted.countDown(); | ||
}); | ||
try { | ||
// This sleep call "ensures" that the statment pool.reserve(queryResourceId2) is called before we release the | ||
// latch (that will cause Thread1 to release the acquired resources). It still doesn't guarantee the previous | ||
// statement, however that's the best we can do, given that reserve() is blocking | ||
Thread.sleep(5_000); | ||
} | ||
catch (InterruptedException e) { | ||
Assert.fail("Interrupted while sleeping"); | ||
} | ||
reserveCalledBySecondThread.countDown(); | ||
}); | ||
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try { | ||
threadsCompleted.await(); | ||
} | ||
catch (InterruptedException e) { | ||
Assert.fail("Interrupted while waiting for the threads to complete"); | ||
} | ||
} | ||
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@Test | ||
public void testMultipleSimultaneousAllocationAttemptsFail() | ||
{ | ||
BlockingPool<ByteBuffer> mergeBufferPool = new DefaultBlockingPool<>(() -> ByteBuffer.allocate(100), 1); | ||
GroupByResourcesReservationPool groupByResourcesReservationPool = | ||
new GroupByResourcesReservationPool(mergeBufferPool, CONFIG); | ||
QueryResourceId queryResourceId = new QueryResourceId("test-id"); | ||
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groupByResourcesReservationPool.reserve(queryResourceId, QUERY, true); | ||
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Assert.assertThrows( | ||
DruidException.class, | ||
() -> groupByResourcesReservationPool.reserve(queryResourceId, QUERY, true) | ||
); | ||
} | ||
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@Test | ||
public void testMultipleSequentialAllocationAttemptsSucceed() | ||
{ | ||
BlockingPool<ByteBuffer> mergeBufferPool = new DefaultBlockingPool<>(() -> ByteBuffer.allocate(100), 1); | ||
GroupByResourcesReservationPool groupByResourcesReservationPool = | ||
new GroupByResourcesReservationPool(mergeBufferPool, CONFIG); | ||
QueryResourceId queryResourceId = new QueryResourceId("test-id"); | ||
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groupByResourcesReservationPool.reserve(queryResourceId, QUERY, true); | ||
GroupByQueryResources oldResources = groupByResourcesReservationPool.fetch(queryResourceId); | ||
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// Cleanup the resources | ||
groupByResourcesReservationPool.clean(queryResourceId); | ||
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// Repeat the calls | ||
groupByResourcesReservationPool.reserve(queryResourceId, QUERY, true); | ||
GroupByQueryResources newResources = groupByResourcesReservationPool.fetch(queryResourceId); | ||
Assert.assertNotNull(newResources); | ||
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Assert.assertNotSame(oldResources, newResources); | ||
} | ||
} |
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I don't think we should add new unit tests that have sleeps; the test suite takes long enough to run already. They are also a sign of a test that is not robust.
Is it possible to rewrite this test to not use a sleep? If not, I'd suggest having it be
@Ignore
so it doesn't run on every test suite run. Then include a comment in the code ofGroupByResourcesReservationPool
itself that says if a future developer is changing the logic, they should run this test manually to ensure they aren't introducing a deadlock.There was a problem hiding this comment.
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The problem I am running into at this point is that I want to signal to Thread1 that Thread2 has called the
reserve()
operation, however, the reserve() itself is blocking. I have tried the polling approach, using synchronized blocks and the current method, however they all run into the same blocker - there's no way to signal from a thread that it has called a blocking operation (before its completion). Any suggestions on how I can achieve this?Else I'll annotate the test with
@Ignore