Lite Topic (RocketMQ 5.x)

Audience: RocketMQ 5.x users who need lightweight, hierarchical messaging — many logical sub-topics inside one physical parent topic, with server-managed offsets and no per-lite-queue consumer plumbing.

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What it is

Lite Topic is RocketMQ 5.5+'s hierarchical message container (RIP-83). A Lite Topic lives inside a normal parent topic declared as LITE type; individual lite queues inside it share the parent's storage, so creating thousands of logical topics costs almost nothing.

EventMesh exposes Lite Topic over the same HTTP surface as regular topics:

Operation	Endpoint	Notes
Create (idempotent)	POST /events/lite/create	Parent must be LITE type
Publish	POST /events/lite/publish / publish-bytes	To a lite queue inside the parent
Poll	GET /events/lite/poll / poll-bytes	Batch poll like regular long-poll

The -bytes variants carry raw binary payloads without JSON encoding.

Semantics — and how they differ from regular topics

Lite Topic trades the runtime's full reliability machinery for RocketMQ-native simplicity:

Property	Regular topics	Lite Topic
Offset ownership	EventMesh runtime (ACK-driven)	Storage plugin (managed inside the plugin)
ACK / DLQ	Explicit ACK, retries, DLQ	None — consumption is poll-and-forget
Ordering	Per partition (LOAD_BALANCE_STICKY per key)	Per lite queue
Backend	Kafka / RocketMQ 4.x / 5.x	RocketMQ 5.x only (LiteTopicCapable)

Use Lite Topic for high-fanout, low-ceremony channels (presence, metrics, chat rooms); use regular topics where unacked-redelivery and dead-lettering matter.

Checkpointing and crash replay

The storage plugin periodically persists each lite queue's pull offset to disk (default every 5 s):

eventmesh.rocketmq5.lite.checkpoint.interval.ms=5000

• A JVM crash replays at most one interval's worth of messages.
• Shutdown always persists regardless of the interval.
• <= 0 disables periodic checkpointing (persist on shutdown only).

SDK

client.createLiteTopic("chat", "room-42");           // idempotent
client.publishLite("chat", "room-42", event);
client.subscribeLite("chat", "room-42", event -> { ... }); // background poll loop
client.unsubscribeLite("chat", "room-42");

subscribeLite runs a background poll loop with plugin-managed offsets — no ACK calls, no DLQ.

Where the code lives

Piece	Location
SPI capability marker	eventmesh-storage-plugin/eventmesh-storage-api/.../storage/LiteTopicCapable.java
RocketMQ 5.x implementation	eventmesh-storage-plugin/eventmesh-storage-rocketmq5/
HTTP endpoints	eventmesh-runtime/.../http/UniHttpServer.java (liteCreate, litePublish, litePoll)
SDK	eventmesh-sdks/.../cloudevents/CloudEventsClient.java (*Lite methods)
Tests	RocketMQ5LiteHttpIntegrationTest, MeshStoragePluginTCK (LiteTopic contract)