Apache Pulsar uses partitioned topics to scale message throughput and parallelism. But sometimes your system grows and your topics need to scale with it. That’s where repartitioning comes in.
In this quick guide, we’ll show you how to change the number of partitions on a topic using the web interface. No manual edits, no CLI required. Just a few clicks.
To get started, open the Explorer page. This is your main starting point for interacting with your Pulsar environment.
Once you are on the Explorer page, you'll see a list of tenants, the logical groups that help organize your messaging infrastructure. Each tenant contains one or more namespaces, which in turn contain the actual topics where your messages live.
Here’s a quick path through the structure:
This clear hierarchy ensures you always know exactly where you are in the system.
Once you’ve selected a topic, you’ll land on its overview page. This page gives you general information about the topic, such as its configuration and metrics.
Look for the Manage button and click on it. In the context menu that opens, select Add Partitions.
Then enter your desired number of partitions and click on Confirm.
Note: You can only increase the number of partitions. Decreasing the number of partitions is not supported in Pulsar.
After confirming, the system handles everything behind the scenes, no downtime or manual intervention is required.
You might ask yourself why you want to repartition a topic. Partitioning improves parallelism and scalability by letting multiple consumers process messages independently.
If you notice performance bottlenecks, or you are onboarding more consumers, increasing partitions can help balance the load more evenly.
Repartitioning a Pulsar topic is a powerful but simple operation when managing Pulsar clusters. With our Pulsar UI, you can increase the throughput and improve performance in just a few clicks. Try it out next time your streams are growing faster than expected or you just want to optimize your pipelines!
