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/*
 * Copyright 2019-present HiveMQ GmbH
 *
 * Licensed 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 com.hivemq.persistence;

import com.google.common.annotations.VisibleForTesting;
import com.hivemq.configuration.service.InternalConfigurations;
import com.hivemq.extension.sdk.api.annotations.NotNull;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.inject.Inject;
import java.util.concurrent.Executor;

/**
 * @author Daniel Krüger
 *         

* This SingleWriterService implementation does not use ExecutorThreadpools, but a trampoline approach like * RxJava Schedulers.trampoline() * The advantage is that there are less thread switches (resulting in context switches). * The requirement is that no submitted task is blocking (that is only true for in-memory persistences) */ public class InMemorySingleWriter implements SingleWriterService { private static final @NotNull Logger log = LoggerFactory.getLogger(SingleWriterServiceImpl.class); private static final int AMOUNT_OF_PRODUCERS = 5; private static final int RETAINED_MESSAGE_QUEUE_INDEX = 0; private static final int CLIENT_SESSION_QUEUE_INDEX = 1; private static final int SUBSCRIPTION_QUEUE_INDEX = 2; private static final int QUEUED_MESSAGES_QUEUE_INDEX = 3; private static final int ATTRIBUTE_STORE_QUEUE_INDEX = 4; private final @NotNull InMemoryProducerQueues @NotNull [] producers = new InMemoryProducerQueues[AMOUNT_OF_PRODUCERS]; private final @NotNull InMemoryProducerQueues callbackProducerQueue; private final int persistenceBucketCount; @Inject public InMemorySingleWriter() { persistenceBucketCount = InternalConfigurations.PERSISTENCE_BUCKET_COUNT.get(); final int threadPoolSize = InternalConfigurations.SINGLE_WRITER_THREAD_POOL_SIZE.get(); final int creditsPerExecution = InternalConfigurations.SINGLE_WRITER_CREDITS_PER_EXECUTION.get(); final int amountOfQueues = validAmountOfQueues(threadPoolSize, persistenceBucketCount); for (int i = 0; i < producers.length; i++) { producers[i] = new InMemoryProducerQueues(persistenceBucketCount, amountOfQueues); } callbackProducerQueue = new InMemoryProducerQueues(persistenceBucketCount, amountOfQueues); } @VisibleForTesting int validAmountOfQueues(final int processorCount, final int bucketCount) { for (int i = processorCount; i < bucketCount; i++) { if (bucketCount % i == 0) { return i; } } return persistenceBucketCount; } public @NotNull ProducerQueues getRetainedMessageQueue() { return producers[RETAINED_MESSAGE_QUEUE_INDEX]; } public @NotNull ProducerQueues getClientSessionQueue() { return producers[CLIENT_SESSION_QUEUE_INDEX]; } public @NotNull ProducerQueues getSubscriptionQueue() { return producers[SUBSCRIPTION_QUEUE_INDEX]; } public @NotNull ProducerQueues getQueuedMessagesQueue() { return producers[QUEUED_MESSAGES_QUEUE_INDEX]; } public @NotNull ProducerQueues getAttributeStoreQueue() { return producers[ATTRIBUTE_STORE_QUEUE_INDEX]; } public @NotNull Executor callbackExecutor(final @NotNull String key) { return command -> callbackProducerQueue.submit(key, (bucketIndex) -> { command.run(); return null; // this is fine, because Executors dont return anything. The return value will not be used. }); } public int getPersistenceBucketCount() { return persistenceBucketCount; } public void stop() { if (log.isTraceEnabled()) { log.trace("Shutting down single writer"); } } }





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