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Fix race condition in LazyDeserializer initialization (#59) (#61)
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Co-authored-by: Sylvain Wallez <sylvain@elastic.co>
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github-actions[bot] and swallez authored Dec 14, 2021
1 parent f5070c7 commit aea0114
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Showing 2 changed files with 74 additions and 4 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -41,14 +41,15 @@ class LazyDeserializer<T> extends DelegatingDeserializer.SameType<T> {
protected JsonpDeserializer<T> unwrap() {
// See SEI CERT LCK10-J https://wiki.sei.cmu.edu/confluence/x/6zdGBQ
JsonpDeserializer<T> d = deserializer;
if (d == null) {
if (d != null) {
return d;
} else {
synchronized (this) {
if (deserializer == null) {
d = ctor.get();
deserializer = d;
deserializer = ctor.get();
}
}
return deserializer;
}
return d;
}
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,69 @@
/*
* Licensed to Elasticsearch B.V. under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch B.V. 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 co.elastic.clients.json;

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

import java.util.concurrent.CompletableFuture;

public class LazyDeserializerTest extends Assert {


@Test
public void testConcurrentInit() throws Exception {
// See https://github.com/elastic/elasticsearch-java/issues/58

final LazyDeserializer<String> ld = new LazyDeserializer<>(JsonpDeserializer::stringDeserializer);

CompletableFuture<JsonpDeserializer<String>> fut1;
CompletableFuture<JsonpDeserializer<String>> fut2;

// Lock the mutex and start 2 threads that will compete for it.
synchronized (ld) {
fut1 = futureUnwrap(ld);
fut2 = futureUnwrap(ld);
}

// We should see the same non-null results everywhere
assertNotNull(fut1.get());
assertNotNull(fut2.get());

final JsonpDeserializer<String> unwrapped = ld.unwrap();
assertEquals(unwrapped, fut1.get());
assertEquals(unwrapped, fut2.get());

}

private CompletableFuture<JsonpDeserializer<String>> futureUnwrap(LazyDeserializer<String> d) {

final CompletableFuture<JsonpDeserializer<String>> result = new CompletableFuture<>();

new Thread(() -> {
try {
result.complete(d.unwrap());
} catch (Throwable e) {
result.completeExceptionally(e);
}
}).start();

return result;
}
}

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