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new 58d439a1aa9 KAFKA-14768 Add latency optimization guidance to
KafkaProducer.send() (#20842)
58d439a1aa9 is described below
commit 58d439a1aa923a098e5ac3e167750219a71f36f9
Author: Jian <[email protected]>
AuthorDate: Thu Nov 13 01:59:12 2025 +0800
KAFKA-14768 Add latency optimization guidance to KafkaProducer.send()
(#20842)
Background: There have been many similar issues discussed about send
latency (block for first sent) in JIRA and KIPs. After diving deep into
the code and weighing the effort versus the reward, I think the most
suitable approach might be to simply add a guideline in the JavaDoc to
help more people become aware of it and understand possible solutions
so that many persons can reduce work load for deep dive this similar
issue.
FYI: The similar JIRAs https://issues.apache.org/jira/browse/KAFKA-6705
https://issues.apache.org/jira/browse/KAFKA-3539
https://issues.apache.org/jira/browse/KAFKA-14768
Reviewers: Chia-Ping Tsai <[email protected]>
---
.../java/org/apache/kafka/clients/producer/KafkaProducer.java | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git
a/clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java
b/clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java
index 6e656f590e4..9672b595e36 100644
--- a/clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java
+++ b/clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java
@@ -937,8 +937,14 @@ public class KafkaProducer<K, V> implements Producer<K, V>
{
* once the record has been stored in the buffer of records waiting to be
sent.
* This allows sending many records in parallel without blocking to wait
for the response after each one.
* Can block for the following cases: 1) For the first record being sent
to
- * the cluster by this client for the given topic. In this case it will
block for up to {@code max.block.ms} milliseconds if
- * Kafka cluster is unreachable; 2) Allocating a buffer if buffer pool
doesn't have any free buffers.
+ * the cluster by this client for the given topic. In this case it will
block for up to {@code max.block.ms} milliseconds
+ * while waiting for topic's metadata if Kafka cluster is unreachable; 2)
Allocating a buffer if buffer pool doesn't
+ * have any free buffers.
+ * <p>
+ * <b>Reducing first-send latency:</b> You can reduce the latency of the
first send by preloading the metadata
+ * with {@link #partitionsFor(String)}. However, be aware that metadata
cache will be cleared to free up resources after
+ * {@code metadata.max.idle.ms} of inactivity, so subsequent sends after a
long idle period will still
+ * experience delays.
* <p>
* The result of the send is a {@link RecordMetadata} specifying the
partition the record was sent to, the offset
* it was assigned and the timestamp of the record. If the producer is
configured with acks = 0, the {@link RecordMetadata}
@@ -1036,6 +1042,7 @@ public class KafkaProducer<K, V> implements Producer<K,
V> {
* @throws InterruptException If the thread is interrupted while
blocked
* @throws SerializationException If the key or value are not valid
objects given the configured serializers
* @throws KafkaException If a Kafka related error occurs that
does not belong to the public API exceptions.
+ * @see #partitionsFor(String)
*/
@Override
public Future<RecordMetadata> send(ProducerRecord<K, V> record, Callback
callback) {
