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

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## Key Components

### Core Classes

- **Crawler** (`Crawler.java`): Main orchestrator - `execute()`, `addUrl()`, `cleanup()`, `stop()`
- **CrawlerContext** (`CrawlerContext.java`): Execution context - `sessionId`, `status`, `accessCount`, `numOfThread`, `maxDepth`, `maxAccessCount`

import jakarta.annotation.Resource;
import jakarta.servlet.http.HttpServletRequest;

/**
 * Client class for RAG (Retrieval-Augmented Generation) chat functionality.
 *
 * Orchestrates the multi-phase RAG workflow including session management,
 * document search, and delegation to LlmClientManager for LLM operations.
 * Prompt construction and LLM-specific logic is handled by LlmClient implementations.
 *