* <ul>
 *   <li>Retry up to 5 times</li>
 *   <li>Wait 500ms between retries</li>
 * </ul>
 *
 */
public class FaultTolerantClient implements CrawlerClient {

    /** Logger instance for this class */
    private static final Logger logger = LogManager.getLogger(FaultTolerantClient.class);

    /** The underlying crawler client */
    protected CrawlerClient client;

    /** Maximum number of retry attempts */

package org.codelibs.fess.crawler.client.http;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.codelibs.fess.crawler.client.CrawlerClient;
import org.codelibs.fess.crawler.client.FaultTolerantClient;

/**
 * SwitchableHttpClient is a switchable HTTP client that can use either Apache HttpComponents 4.x or 5.x.
 * The client implementation is selected based on the system property {@code fess.crawler.http.client}.
 *

**Resource Management**: `AutoCloseable` throughout, `DeferredFileOutputStream` for large responses, connection pooling, background temp file deletion via `FileUtil.deleteInBackground()`

**Fault Tolerance**: `FaultTolerantClient` wrapper (retry, circuit breaker), `SwitchableHttpClient` for HTTP client fallback

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## Key Components

### Core Classes