[Bug] BrokerData.selectBrokerAddr crashes for an empty address table

[yuluo-yx]

Before Creating the Bug Report

• I found a bug, not just a question.
• I searched open GitHub Issues and pull requests and found no duplicate.
• I confirmed that this bug belongs to Apache RocketMQ.

Runtime platform environment

macOS (Darwin), reproduced with an isolated local unit test.

RocketMQ version

Branch: develop
Git commit: fd0c959

JDK Version

Zulu OpenJDK 8 (8.94.0.17)

Describe the Bug

BrokerData.selectBrokerAddr assumes brokerAddrs is non-null and non-empty. A default BrokerData instance throws NullPointerException, while an empty map reaches Random.nextInt(0) and throws IllegalArgumentException.

Steps to Reproduce

1. Create a default BrokerData and call selectBrokerAddr.
2. Alternatively, set brokerAddrs to an empty HashMap and call selectBrokerAddr.
3. Observe the exception.

What Did You Expect to See?

The method should return null when no broker address is registered, consistent with its nullable selection result.

What Did You See Instead?

The method throws for both null and empty address tables.

Additional Context

Master preference and slave fallback remain valid; only the no-address boundary is affected.

[RockteMQ-AI]

Issue Evaluation

Category: type/bug | Status: Confirmed

Root Cause: BrokerData.selectBrokerAddr assumes brokerAddrs is non-null and non-empty. A default BrokerData instance throws NullPointerException, while an empty map reaches Random.nextInt(0) and throws IllegalArgumentException.
Impact: Broker address selection — callers that invoke selectBrokerAddr before broker registration completes will encounter unhandled exceptions instead of a graceful null return.
Severity: medium

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Automated evaluation by github-manager-bot