org.graylog2.streams.DefaultStreamChangeHandler 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.streams;

import com.google.common.eventbus.EventBus;
import com.google.common.eventbus.Subscribe;
import org.graylog2.bindings.providers.DefaultStreamProvider;
import org.graylog2.plugin.streams.Stream;
import org.graylog2.streams.events.StreamsChangedEvent;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.inject.Inject;
import javax.inject.Singleton;

/**
 * This class subscribes to all {@link StreamsChangedEvent} events and reloads the default stream if it has changed.
 *
 * We need this because the default Stream instance is only loaded once when it is first accessed. (see {@link DefaultStreamProvider#get()})
 * Without this, changes to the default stream would only be applied after a server restart.
 */
@Singleton
public class DefaultStreamChangeHandler {
    private static final Logger LOG = LoggerFactory.getLogger(DefaultStreamChangeHandler.class);

    private final StreamService streamService;
    private final DefaultStreamProvider defaultStreamProvider;

    @Inject
    public DefaultStreamChangeHandler(StreamService streamService,
                                      DefaultStreamProvider defaultStreamProvider,
                                      EventBus eventBus) {
        this.streamService = streamService;
        this.defaultStreamProvider = defaultStreamProvider;

        // TODO: This class needs lifecycle management to avoid leaking objects in the EventBus
        eventBus.register(this);
    }

    @Subscribe
    public void handleStreamsChange(StreamsChangedEvent event) {
        event.streamIds().stream()
                .filter(Stream.DEFAULT_STREAM_ID::equals)
                .findFirst().ifPresent(streamId -> reloadDefaultStream());
    }

    private void reloadDefaultStream() {
        try {
            LOG.debug("Attempting to reload and set default stream");
            defaultStreamProvider.setDefaultStream(streamService.load(Stream.DEFAULT_STREAM_ID));
        } catch (Exception e) {
            LOG.error("Couldn't reload default stream", e);
        }
    }
}