KAFKA-13761: KafkaLog4jAppender deadlocks when idempotence is enabled (#11939)

When a log entry is appended to a Kafka topic using KafkaLog4jAppender, the producer.send operation
may hit a deadlock if the producer network thread also tries to append a log at the same log level.
This issue is triggered when idempotence is enabled for the KafkaLog4jAppender and the producer
tries to acquire the TransactionManager lock.

This is a temporary workaround to avoid deadlocks by disabling idempotence explicitly in
KafkaLog4jAppender.

Reviewers: Luke Chen <showuon@gmail.com>, Ismael Juma <ismael@juma.me.uk>

log4j-appender/src/main/java/org/apache/kafka/log4jappender/KafkaLog4jAppender.java

@@ -43,6 +43,7 @@ import static org.apache.kafka.clients.producer.ProducerConfig.LINGER_MS_CONFIG;
 import static org.apache.kafka.clients.producer.ProducerConfig.MAX_BLOCK_MS_CONFIG;
 import static org.apache.kafka.clients.producer.ProducerConfig.RETRIES_CONFIG;
 import static org.apache.kafka.clients.producer.ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG;
+import static org.apache.kafka.clients.producer.ProducerConfig.ENABLE_IDEMPOTENCE_CONFIG;
 import static org.apache.kafka.common.config.SaslConfigs.SASL_JAAS_CONFIG;
 import static org.apache.kafka.common.config.SaslConfigs.SASL_KERBEROS_SERVICE_NAME;
 import static org.apache.kafka.common.config.SaslConfigs.SASL_MECHANISM;
@@ -290,6 +291,9 @@ public class KafkaLog4jAppender extends AppenderSkeleton {
         props.put(DELIVERY_TIMEOUT_MS_CONFIG, deliveryTimeoutMs);
         props.put(LINGER_MS_CONFIG, lingerMs);
         props.put(BATCH_SIZE_CONFIG, batchSize);
+        // Disable idempotence to avoid deadlock when the producer network thread writes a log line while interacting
+        // with the TransactionManager, see KAFKA-13761 for more information.
+        props.put(ENABLE_IDEMPOTENCE_CONFIG, false);
 
         if (securityProtocol != null) {
             props.put(SECURITY_PROTOCOL_CONFIG, securityProtocol);