---

title: Partitioned topics lead: Expand message throughput by distributing load within topics tags:

• topics
• partitioning
• admin
• clients

---

By default, Pulsar {% popover topics %} are served by a single {% popover broker %}. Using only a single broker, however, limits a topic's maximum throughput. Partitioned topics are a special type of topic that can span multiple brokers and thus allow for much higher throughput. For an explanation of how partitioned topics work, see the Concepts section below.

You can publish to partitioned topics using Pulsar‘s client libraries and you can create and manage partitioned topics using Pulsar’s admin API.

Publishing to partitioned topics

When publishing to partitioned topics, the only difference from non-partitioned topics is that you need to specify a routing mode when you create a new {% popover producer %}. Examples for Java are below.

Java

Publishing messages to partitioned topics in the Java client works much like publishing to normal topics. The difference is that you need to specify either one of the currently available message routers or a custom router.

Routing mode

You can specify the routing mode in the {% javadoc ProducerConfiguration client org.apache.pulsar.client.api.ProducerConfiguration %} object that you use to configure your producer. You have three options:

• SinglePartition
• RoundRobinPartition
• CustomPartition

Here's an example:

String pulsarBrokerRootUrl = "pulsar://localhost:6650";
String topic = "persistent://my-property/my-cluster-my-namespace/my-topic";

PulsarClient client = PulsarClient.create(pulsarBrokerRootUrl);
ProducerConfiguration config = new ProducerConfiguration();
config.setMessageRoutingMode(ProducerConfiguration.MessageRoutingMode.SinglePartition);
Producer producer = client.createProducer(topic, config);
producer.send("Partitioned topic message".getBytes());

Custom message router

To use a custom message router, you need to provide an implementation of the {% javadoc MessageRouter client org.apache.pulsar.client.api.MessageRouter %} interface, which has just one choosePartition method:

public interface MessageRouter extends Serializable {
    int choosePartition(Message msg);
}

Here's a (not very useful!) router that routes every message to partition 10:

public class AlwaysTenRouter implements MessageRouter {
    public int choosePartition(Message msg) {
        return 10;
    }
}

With that implementation in hand, you can send

String pulsarBrokerRootUrl = "pulsar://localhost:6650";
String topic = "persistent://my-property/my-cluster-my-namespace/my-topic";

PulsarClient client = PulsarClient.create(pulsarBrokerRootUrl);
ProducerConfiguration config = new ProducerConfiguration();
config.setMessageRouter(AlwaysTenRouter);
Producer producer = client.createProducer(topic, config);
producer.send("Partitioned topic message".getBytes());

Pulsar admin setup

{% include explanations/admin-setup.md %}

Managing partitioned topics

{% include explanations/partitioned-topic-admin.md %}

Concepts

{% include explanations/partitioned-topics.md %}