org.apache.nifi.distributed.cache.server.DistributedCacheServer Maven / Gradle / Ivy

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.nifi.distributed.cache.server;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.nifi.annotation.lifecycle.OnEnabled;
import org.apache.nifi.annotation.lifecycle.OnShutdown;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.controller.AbstractControllerService;
import org.apache.nifi.controller.ConfigurationContext;
import org.apache.nifi.processor.util.StandardValidators;
import org.apache.nifi.ssl.SSLContextService;

public abstract class DistributedCacheServer extends AbstractControllerService {
    public static final String EVICTION_STRATEGY_LFU = "Least Frequently Used";
    public static final String EVICTION_STRATEGY_LRU = "Least Recently Used";
    public static final String EVICTION_STRATEGY_FIFO = "First In, First Out";

    public static final PropertyDescriptor PORT = new PropertyDescriptor.Builder()
            .name("Port")
            .description("The port to listen on for incoming connections")
            .required(true)
            .addValidator(StandardValidators.PORT_VALIDATOR)
            .defaultValue("4557")
            .build();
    public static final PropertyDescriptor SSL_CONTEXT_SERVICE = new PropertyDescriptor.Builder()
            .name("SSL Context Service")
            .description(
                    "If specified, this service will be used to create an SSL Context that will be used to secure communications; if not specified, communications will not be secure")
            .required(false)
            .addValidator(StandardValidators.createControllerServiceExistsValidator(SSLContextService.class))
            .build();
    public static final PropertyDescriptor MAX_CACHE_ENTRIES = new PropertyDescriptor.Builder()
            .name("Maximum Cache Entries")
            .description("The maximum number of cache entries that the cache can hold")
            .required(true)
            .addValidator(StandardValidators.POSITIVE_INTEGER_VALIDATOR)
            .defaultValue("10000")
            .build();
    public static final PropertyDescriptor EVICTION_POLICY = new PropertyDescriptor.Builder()
            .name("Eviction Strategy")
            .description("Determines which strategy should be used to evict values from the cache to make room for new entries")
            .required(true)
            .allowableValues(EVICTION_STRATEGY_LFU, EVICTION_STRATEGY_LRU, EVICTION_STRATEGY_FIFO)
            .defaultValue(EVICTION_STRATEGY_LFU)
            .build();
    public static final PropertyDescriptor PERSISTENCE_PATH = new PropertyDescriptor.Builder()
            .name("Persistence Directory")
            .description("If specified, the cache will be persisted in the given directory; if not specified, the cache will be in-memory only")
            .required(false)
            .addValidator(StandardValidators.createDirectoryExistsValidator(true, true))
            .build();

    private volatile CacheServer cacheServer;

    @Override
    protected List getSupportedPropertyDescriptors() {
        final List properties = new ArrayList<>();
        properties.add(PORT);
        properties.add(MAX_CACHE_ENTRIES);
        properties.add(EVICTION_POLICY);
        properties.add(PERSISTENCE_PATH);
        properties.add(new PropertyDescriptor.Builder().fromPropertyDescriptor(SSL_CONTEXT_SERVICE).allowableValues(
                getControllerServiceLookup().getControllerServiceIdentifiers(SSLContextService.class)).build());
        return properties;
    }

    @OnEnabled
    public void startServer(final ConfigurationContext context) throws IOException {
        if (cacheServer == null) {
            cacheServer = createCacheServer(context);
            cacheServer.start();
        }
    }

    @OnShutdown
    public void shutdownServer() throws IOException {
        if (cacheServer != null) {
            cacheServer.stop();
        }
        cacheServer = null;
    }

    @Override
    protected void finalize() throws Throwable {
        shutdownServer();
    }

    protected abstract CacheServer createCacheServer(ConfigurationContext context);
}