slider-core/src/main/java/org/apache/slider/server/services/curator/CuratorHelper.java

/*
 * 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.slider.server.services.curator;

import com.google.common.base.Preconditions;
import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.x.discovery.ServiceDiscovery;
import org.apache.curator.x.discovery.ServiceDiscoveryBuilder;
import org.apache.curator.x.discovery.strategies.RandomStrategy;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.slider.core.registry.info.ServiceInstanceData;
import org.apache.slider.server.services.registry.RegistryServiceConstants;
import org.apache.slider.server.services.registry.RegistryDiscoveryContext;
import org.apache.slider.server.services.registry.SliderRegistryService;

/**
 * This class creates a curator -but does not start or close it. That
 * is the responsbility of the owner
 */
public class CuratorHelper extends Configured {

  private final CuratorFramework curator;
  private final String connectionString;

  public CuratorHelper(Configuration conf, String connectionString) {
    super(conf);
    this.connectionString = connectionString;
    curator = createCurator(this.connectionString);
  }


  public CuratorFramework getCurator() {
    return curator;
  }

  public String getConnectionString() {
    return connectionString;
  }

  /**
   * Create a retry policy for this configuration
   * @param conf
   * @return
   */
  public RetryPolicy createRetryPolicy() {
    RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);
    return retryPolicy;
  }

  private CuratorFramework createCurator(String connectionString) {
    CuratorFramework curator =
      CuratorFrameworkFactory.newClient(connectionString,
                                        createRetryPolicy());
    return curator;
  }

  /**
   * Create an (united) curator client service
   * @param connectionString ZK binding
   * @return the service
   */
  public CuratorService createCuratorClientService() {
    CuratorService curatorService =
      new CuratorService("Curator ", curator, connectionString);
    return curatorService;
  }

  /**
   * Create a discovery builder bonded to this curator
   * @return
   */
  public ServiceDiscoveryBuilder<ServiceInstanceData> createDiscoveryBuilder() {
    ServiceDiscoveryBuilder<ServiceInstanceData> discoveryBuilder =
      ServiceDiscoveryBuilder.builder(ServiceInstanceData.class);
    discoveryBuilder.client(curator);
    return discoveryBuilder;
  }

  /**
   * Create an instance
   * @param discoveryBuilder builder to create the discovery from
   */

  public SliderRegistryService createRegistryBinderService(
      String basePath,
      ServiceDiscoveryBuilder<ServiceInstanceData> discoveryBuilder) {
    discoveryBuilder.basePath(basePath);
    return new SliderRegistryService(curator,
        basePath,
        discoveryBuilder.build());
  }


  /**
   * Create an instance -including the initial binder
   * @param basePath base path
   * @return the binder service
   */
  public SliderRegistryService createRegistryBinderService(
    String basePath) {
    ServiceDiscoveryBuilder<ServiceInstanceData> discoveryBuilder =
      createDiscoveryBuilder();
    //registry will start curator as well as the binder, in the correct order
    SliderRegistryService registryBinderService =
      createRegistryBinderService(basePath, discoveryBuilder);
    return registryBinderService;
  }

  public RegistryDiscoveryContext createDiscoveryContext(
    ServiceDiscovery<ServiceInstanceData> discovery) {
    Preconditions.checkNotNull(discovery);
    return new RegistryDiscoveryContext(discovery,
                                        new RandomStrategy<ServiceInstanceData>(),
                                        RegistryServiceConstants.INSTANCE_REFRESH_MS,
                                        ServiceInstanceData.class);

  }
}