org.graylog2.storage.providers.AtomicCache Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of graylog2-server Show documentation

Graylog

There is a newer version: 6.1.4

/*
 * 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();
        }
    }
}