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import org.apache.kafka.clients.consumer.*;
import org.apache.kafka.clients.consumer.internals.*;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.serialization.ByteArrayDeserializer;
import org.apache.kafka.common.errors.TimeoutException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.*;
/**
* Enhanced test program to reproduce and diagnose the seekToBeginning() hang issue
*
* This test:
* 1. Adds detailed logging of Kafka client operations
* 2. Captures exceptions and timeouts
* 3. Shows what the consumer is waiting for
* 4. Tracks request/response lifecycle
*/
public class SeekToBeginningTest {
private static final Logger log = LoggerFactory.getLogger(SeekToBeginningTest.class);
public static void main(String[] args) throws Exception {
String bootstrapServers = "localhost:9093";
String topicName = "_schemas";
if (args.length > 0) {
bootstrapServers = args[0];
}
Properties props = new Properties();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
props.put(ConsumerConfig.GROUP_ID_CONFIG, "test-seek-group");
props.put(ConsumerConfig.CLIENT_ID_CONFIG, "test-seek-client");
props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "false");
props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, ByteArrayDeserializer.class);
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, ByteArrayDeserializer.class);
props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, "45000");
props.put(ConsumerConfig.REQUEST_TIMEOUT_MS_CONFIG, "60000");
// Add comprehensive debug logging
props.put("log4j.logger.org.apache.kafka.clients.consumer.internals", "DEBUG");
props.put("log4j.logger.org.apache.kafka.clients.producer.internals", "DEBUG");
props.put("log4j.logger.org.apache.kafka.clients.Metadata", "DEBUG");
// Add shorter timeouts to fail faster
props.put(ConsumerConfig.DEFAULT_API_TIMEOUT_MS_CONFIG, "10000"); // 10 seconds instead of 60
System.out.println("\n╔════════════════════════════════════════════════════════════╗");
System.out.println("║ SeekToBeginning Diagnostic Test ║");
System.out.println(String.format("║ Connecting to: %-42s║", bootstrapServers));
System.out.println("╚════════════════════════════════════════════════════════════╝\n");
System.out.println("[TEST] Creating KafkaConsumer...");
System.out.println("[TEST] Bootstrap servers: " + bootstrapServers);
System.out.println("[TEST] Group ID: test-seek-group");
System.out.println("[TEST] Client ID: test-seek-client");
KafkaConsumer<byte[], byte[]> consumer = new KafkaConsumer<>(props);
TopicPartition tp = new TopicPartition(topicName, 0);
List<TopicPartition> partitions = Arrays.asList(tp);
System.out.println("\n[STEP 1] Assigning to partition: " + tp);
consumer.assign(partitions);
System.out.println("[STEP 1] ✓ Assigned successfully");
System.out.println("\n[STEP 2] Calling seekToBeginning()...");
long startTime = System.currentTimeMillis();
try {
consumer.seekToBeginning(partitions);
long seekTime = System.currentTimeMillis() - startTime;
System.out.println("[STEP 2] ✓ seekToBeginning() completed in " + seekTime + "ms");
} catch (Exception e) {
System.out.println("[STEP 2] ✗ EXCEPTION in seekToBeginning():");
e.printStackTrace();
consumer.close();
return;
}
System.out.println("\n[STEP 3] Starting poll loop...");
System.out.println("[STEP 3] First poll will trigger offset lookup (ListOffsets)");
System.out.println("[STEP 3] Then will fetch initial records\n");
int successfulPolls = 0;
int failedPolls = 0;
int totalRecords = 0;
for (int i = 0; i < 3; i++) {
System.out.println("═══════════════════════════════════════════════════════════");
System.out.println("[POLL " + (i + 1) + "] Starting poll with 15-second timeout...");
long pollStart = System.currentTimeMillis();
try {
System.out.println("[POLL " + (i + 1) + "] Calling consumer.poll()...");
ConsumerRecords<byte[], byte[]> records = consumer.poll(java.time.Duration.ofSeconds(15));
long pollTime = System.currentTimeMillis() - pollStart;
System.out.println("[POLL " + (i + 1) + "] ✓ Poll completed in " + pollTime + "ms");
System.out.println("[POLL " + (i + 1) + "] Records received: " + records.count());
if (records.count() > 0) {
successfulPolls++;
totalRecords += records.count();
for (ConsumerRecord<byte[], byte[]> record : records) {
System.out.println(" [RECORD] offset=" + record.offset() +
", key.len=" + (record.key() != null ? record.key().length : 0) +
", value.len=" + (record.value() != null ? record.value().length : 0));
}
} else {
System.out.println("[POLL " + (i + 1) + "] ℹ No records in this poll (but no error)");
successfulPolls++;
}
} catch (TimeoutException e) {
long pollTime = System.currentTimeMillis() - pollStart;
failedPolls++;
System.out.println("[POLL " + (i + 1) + "] ✗ TIMEOUT after " + pollTime + "ms");
System.out.println("[POLL " + (i + 1) + "] This means consumer is waiting for something from broker");
System.out.println("[POLL " + (i + 1) + "] Possible causes:");
System.out.println(" - ListOffsetsRequest never sent");
System.out.println(" - ListOffsetsResponse not received");
System.out.println(" - Broker metadata parsing failed");
System.out.println(" - Connection issue");
// Print current position info if available
try {
long position = consumer.position(tp);
System.out.println("[POLL " + (i + 1) + "] Current position: " + position);
} catch (Exception e2) {
System.out.println("[POLL " + (i + 1) + "] Could not get position: " + e2.getMessage());
}
} catch (Exception e) {
failedPolls++;
long pollTime = System.currentTimeMillis() - pollStart;
System.out.println("[POLL " + (i + 1) + "] ✗ EXCEPTION after " + pollTime + "ms:");
System.out.println("[POLL " + (i + 1) + "] Exception type: " + e.getClass().getSimpleName());
System.out.println("[POLL " + (i + 1) + "] Message: " + e.getMessage());
// Print stack trace for first exception
if (i == 0) {
System.out.println("[POLL " + (i + 1) + "] Stack trace:");
e.printStackTrace();
}
}
}
System.out.println("\n═══════════════════════════════════════════════════════════");
System.out.println("[RESULTS] Test Summary:");
System.out.println(" Successful polls: " + successfulPolls);
System.out.println(" Failed polls: " + failedPolls);
System.out.println(" Total records received: " + totalRecords);
if (failedPolls > 0) {
System.out.println("\n[DIAGNOSIS] Consumer is BLOCKED during poll()");
System.out.println(" This indicates the consumer cannot:");
System.out.println(" 1. Send ListOffsetsRequest to determine offset 0, OR");
System.out.println(" 2. Receive/parse ListOffsetsResponse from broker, OR");
System.out.println(" 3. Parse broker metadata for partition leader lookup");
} else if (totalRecords == 0) {
System.out.println("\n[DIAGNOSIS] Consumer is working but NO records found");
System.out.println(" This might mean:");
System.out.println(" 1. Topic has no messages, OR");
System.out.println(" 2. Fetch is working but broker returns empty");
} else {
System.out.println("\n[SUCCESS] Consumer working correctly!");
System.out.println(" Received " + totalRecords + " records");
}
System.out.println("\n[CLEANUP] Closing consumer...");
try {
consumer.close();
System.out.println("[CLEANUP] ✓ Consumer closed successfully");
} catch (Exception e) {
System.out.println("[CLEANUP] ✗ Error closing consumer: " + e.getMessage());
}
System.out.println("\n[TEST] Done!\n");
}
}
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