content: /*
   * 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.arrow.driver.jdbc.client.utils;
  
  import com.github.benmanes.caffeine.cache.Cache;
  import com.github.benmanes.caffeine.cache.Caffeine;
  import java.time.Duration;
  import org.apache.arrow.util.VisibleForTesting;
  
  /**
   * A cache for Flight clients.
   *
   * <p>The intent is to avoid constantly recreating clients to the same locations. gRPC can multiplex
   * multiple requests over a single TCP connection, and a cache would let us take advantage of that.
   *
   * <p>At the time being it only tracks whether a location is reachable or not. To actually cache
   * clients, we would need a way to incorporate other connection parameters (authentication, etc.)
   * into the cache key.
   */
  public final class FlightClientCache {
    @VisibleForTesting Cache<String, ClientCacheEntry> clientCache;
  
    public FlightClientCache() {
      this.clientCache = Caffeine.newBuilder().expireAfterWrite(Duration.ofSeconds(600)).build();
    }
  
    public boolean isDud(String key) {
      return clientCache.getIfPresent(key) != null;
    }
  
    public void markLocationAsDud(String key) {
      clientCache.put(key, new ClientCacheEntry());
    }
  
    public void markLocationAsReachable(String key) {
      clientCache.invalidate(key);
    }
  
    /** A cache entry (empty because we only track reachability, see outer class docstring). */
    public static final class ClientCacheEntry {}
  }
  