* </p>
 *
 * <p>
 * It also provides thread-local storage for sitemaps, allowing each thread to have its own set of sitemaps.
 * </p>
 */
public class CrawlerContext {
    /**
     * Constructs a new CrawlerContext.
     */
    public CrawlerContext() {
        // Default constructor
    }

    /**
     * Session identifier for the crawling session.
     */
    protected String sessionId;

    /**

        final UrlQueue<?> urlQueue = objs.length > 1 && objs[1] instanceof UrlQueue<?> ? (UrlQueue<?>) objs[1] : null;
        try {
            final CrawlerContext crawlerContext = (CrawlerContext) objs[0];
            final Throwable e = (Throwable) objs[2];

            storeFailureUrl(crawlerContext, urlQueue, e.getClass().getCanonicalName(), e);
        } catch (final ContainerNotAvailableException e) {
            if (logger.isDebugEnabled()) {

                    crawlerContext.getNumOfThread(), crawlerContext.maxDepth, crawlerContext.maxAccessCount);
        }

        // context
        crawlerContext.urlFilter = urlFilter;
        crawlerContext.ruleManager = ruleManager;
        crawlerContext.intervalController = intervalController;

        this.clientFactory = clientFactory;
    }

    /**
     * Sets the crawler context.
     * @param crawlerContext The CrawlerContext instance.
     */
    public void setCrawlerContext(final CrawlerContext crawlerContext) {
        this.crawlerContext = crawlerContext;
    }

            // num of threads
            final CrawlerContext crawlerContext = crawler.getCrawlerContext();
            final int numOfThread =
                    webConfig.getNumOfThread() != null ? webConfig.getNumOfThread() : Constants.DEFAULT_NUM_OF_THREAD_FOR_WEB;
            crawlerContext.setNumOfThread(numOfThread);

            // depth

            assertFalse(crawler1.crawlerContext == crawler2.crawlerContext);

            for (int i = 0; i < 100; i++) {
                if (crawler1.crawlerContext.getStatus() == CrawlerStatus.RUNNING) {
                    break;
                }
                Thread.sleep(50);
            }
            assertEquals(CrawlerStatus.RUNNING, crawler1.crawlerContext.getStatus());

---

## Key Components

### Core Classes

- **Crawler** (`Crawler.java`): Main orchestrator - `execute()`, `addUrl()`, `cleanup()`, `stop()`
- **CrawlerContext** (`CrawlerContext.java`): Execution context - `sessionId`, `status`, `accessCount`, `numOfThread`, `maxDepth`, `maxAccessCount`
- **CrawlerThread** (`CrawlerThread.java`): Worker thread - Poll URL → Validate → Execute → Process → Queue children

            assertFalse(sessionId1 == sessionId2);
            assertFalse(crawler1.crawlerContext == crawler2.crawlerContext);

            // Wait for both crawlers to start with polling
            long startTime = System.currentTimeMillis();
            while ((crawler1.crawlerContext.getStatus() != CrawlerStatus.RUNNING
                    || crawler2.crawlerContext.getStatus() != CrawlerStatus.RUNNING) && System.currentTimeMillis() - startTime < 5000) {

                    log(logHelper, LogType.NOT_MODIFIED, crawlerContext, urlQueue);

                    responseData.setExecutionTime(systemHelper.getCurrentTimeAsLong() - startTime);
                    responseData.setParentUrl(urlQueue.getParentUrl());
                    responseData.setSessionId(crawlerContext.getSessionId());

            // not support robots.txt
            return;
        }

        // crawler context
        final CrawlerContext crawlerContext = CrawlingParameterUtil.getCrawlerContext();
        if (crawlerContext == null) {
            // wrong state
            return;
        }

        final int idx = url.indexOf('/', url.indexOf("://") + 3);
        String hostUrl;