io.zeebe.logstreams.impl.service.LogWriteBufferService Maven / Gradle / Ivy

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/*
 * Copyright © 2017 camunda services GmbH ([email protected])
 *
 * 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 io.zeebe.logstreams.impl.service;

import io.zeebe.dispatcher.Dispatcher;
import io.zeebe.dispatcher.DispatcherBuilder;
import io.zeebe.dispatcher.impl.PositionUtil;
import io.zeebe.logstreams.impl.log.index.LogBlockIndex;
import io.zeebe.logstreams.log.BufferedLogStreamReader;
import io.zeebe.logstreams.log.LoggedEvent;
import io.zeebe.logstreams.spi.LogStorage;
import io.zeebe.servicecontainer.*;

public class LogWriteBufferService implements Service
{
    private final Injector logStorageInjector = new Injector<>();
    private final Injector logBlockIndexInjector = new Injector<>();

    protected DispatcherBuilder dispatcherBuilder;
    protected Dispatcher dispatcher;

    public LogWriteBufferService(DispatcherBuilder builder)
    {
        this.dispatcherBuilder = builder;
    }

    @Override
    public void start(ServiceStartContext ctx)
    {
        ctx.run(() ->
        {
            final int partitionId = determineInitialPartitionId();

            dispatcher = dispatcherBuilder
                .initialPartitionId(partitionId + 1)
                .name(ctx.getName())
                .actorScheduler(ctx.getScheduler())
                .build();
        });
    }

    @Override
    public void stop(ServiceStopContext ctx)
    {
        ctx.async(dispatcher.closeAsync());
    }

    private int determineInitialPartitionId()
    {
        final LogStorage logStorage = logStorageInjector.getValue();
        final LogBlockIndex logBlockIndex = logBlockIndexInjector.getValue();

        try (BufferedLogStreamReader logReader = new BufferedLogStreamReader(true))
        {
            logReader.wrap(logStorage, logBlockIndex);

            long lastPosition = 0;

            // Get position of last entry
            logReader.seekToLastEvent();
            if (logReader.hasNext())
            {
                final LoggedEvent lastEntry = logReader.next();
                lastPosition = lastEntry.getPosition();
            }

            // dispatcher needs to generate positions greater than the last position
            int partitionId = 0;

            if (lastPosition > 0)
            {
                partitionId = PositionUtil.partitionId(lastPosition);
            }

            return partitionId;
        }
    }

    @Override
    public Dispatcher get()
    {
        return dispatcher;
    }

    public Injector getLogBlockIndexInjector()
    {
        return logBlockIndexInjector;
    }

    public Injector getLogStorageInjector()
    {
        return logStorageInjector;
    }
}