Limits of Auto-Topic Creation Memory Overhead in Pulsar Standalone for Low-Traffic Workloads

Memory Impact of Auto‑Topic Creation in Pulsar Standalone

The goal is to quantify how enabling Auto‑Topic Creation influences broker heap consumption when running Pulsar in Standalone mode for a low‑traffic workload.

In Standalone mode the broker, ZooKeeper and BookKeeper share a single JVM, so any per‑topic data structures (metadata, cursors, subscription objects) directly affect the available memory. Low‑traffic workloads generate few messages, but the number of topics that may be created automatically is unpredictable, making it unclear at what point the added overhead begins to constrain heap space or trigger more frequent garbage collection.

What is the approximate per‑topic memory footprint when Auto‑Topic Creation is active? At what count of concurrently auto‑created topics does broker heap usage exceed a given threshold (e.g., 70 % of the configured max heap)? Does enabling this feature noticeably increase GC pause times in a low‑traffic scenario?