ThreadLocalClientProvider.java

/*
 * Copyright © 2012-2014 Cask Data, Inc.
 *
 * 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 co.cask.tephra.distributed;

import org.apache.hadoop.conf.Configuration;
import org.apache.thrift.TException;
import org.apache.twill.discovery.DiscoveryServiceClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.TimeoutException;

/**
 * An tx client provider that uses thread local to maintain at most one open connection per thread.
 * Note that there can be a connection leak if the threads are recycled.
 */
public class ThreadLocalClientProvider extends AbstractClientProvider {

  private static final Logger LOG =
      LoggerFactory.getLogger(ThreadLocalClientProvider.class);

  ThreadLocal<TransactionServiceThriftClient> clients = new ThreadLocal<>();

  public ThreadLocalClientProvider(Configuration conf, DiscoveryServiceClient discoveryServiceClient) {
    super(conf, discoveryServiceClient);
  }

  @Override
  public CloseableThriftClient getCloseableClient() throws TException, TimeoutException, InterruptedException {
    TransactionServiceThriftClient client = this.clients.get();
    if (client == null) {
      try {
        client = this.newClient();
        clients.set(client);
      } catch (TException e) {
        LOG.error("Unable to create new tx client for thread: "
                    + e.getMessage());
        throw e;
      }
    }
    return new CloseableThriftClient(this, client);
  }

  @Override
  public void returnClient(TransactionServiceThriftClient client) {
    if (!client.isValid()) {
      client.close();
      clients.remove();
    }
  }

  @Override
  public String toString() {
    return "Thread-local";
  }
}