org.graylog2.storage.providers.AtomicCache Maven / Gradle / Ivy
/*
* Copyright (C) 2020 Graylog, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* .
*/
package org.graylog2.storage.providers;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;
public class AtomicCache {
private final AtomicReference> value;
public AtomicCache() {
this.value = new AtomicReference<>();
}
public T get(Supplier valueSupplier) throws ExecutionException, InterruptedException {
final CompletableFuture completableFuture = new CompletableFuture<>();
final Future previous = this.value.getAndAccumulate(completableFuture, (prev, cur) -> prev == null ? cur : prev);
if (previous == null) {
try {
final T newValue = valueSupplier.get();
completableFuture.complete(newValue);
return newValue;
} catch (Exception e) {
completableFuture.completeExceptionally(e);
return null;
}
} else {
return previous.get();
}
}
}