apache/rocketmq · error · NullPointerException

allocateMessageQueueStrategy is null

Error message

allocateMessageQueueStrategy is null

What it means

AllocateMachineRoomNearby's constructor requires a non-null delegate AllocateMessageQueueStrategy (the strategy it applies within each machine room after grouping consumers). Passing null throws NullPointerException immediately — a fail-fast constructor contract, since allocation cannot proceed without an inner strategy.

Source

Thrown at client/src/main/java/org/apache/rocketmq/client/consumer/rebalance/AllocateMachineRoomNearby.java:44

import org.apache.rocketmq.common.message.MessageQueue;

/**
 * An allocate strategy proxy for based on machine room nearside priority. An actual allocate strategy can be
 * specified.
 *
 * If any consumer is alive in a machine room, the message queue of the broker which is deployed in the same machine
 * should only be allocated to those. Otherwise, those message queues can be shared along all consumers since there are
 * no alive consumer to monopolize them.
 */
public class AllocateMachineRoomNearby extends AbstractAllocateMessageQueueStrategy {

    private final AllocateMessageQueueStrategy allocateMessageQueueStrategy;//actual allocate strategy
    private final MachineRoomResolver machineRoomResolver;

    public AllocateMachineRoomNearby(AllocateMessageQueueStrategy allocateMessageQueueStrategy,
        MachineRoomResolver machineRoomResolver) throws NullPointerException {
        if (allocateMessageQueueStrategy == null) {
            throw new NullPointerException("allocateMessageQueueStrategy is null");
        }

        if (machineRoomResolver == null) {
            throw new NullPointerException("machineRoomResolver is null");
        }

        this.allocateMessageQueueStrategy = allocateMessageQueueStrategy;
        this.machineRoomResolver = machineRoomResolver;
    }

    @Override
    public List<MessageQueue> allocate(String consumerGroup, String currentCID, List<MessageQueue> mqAll,
        List<String> cidAll) {

        List<MessageQueue> result = new ArrayList<>();
        if (!check(consumerGroup, currentCID, mqAll, cidAll)) {
            return result;
        }

View on GitHub (pinned to 293f588571)

Solutions

1. Supply a concrete inner strategy, e.g. new AllocateMessageQueueAveragely()
2. If wiring via DI, verify the delegate bean exists and the reference resolves
3. Default the delegate: strategy != null ? strategy : new AllocateMessageQueueAveragely()

Example fix

// before
new AllocateMachineRoomNearby(null, resolver);

// after
new AllocateMachineRoomNearby(new AllocateMessageQueueAveragely(), resolver);

AllocateMessageQueueStrategy inner =
    (delegate != null) ? delegate : new AllocateMessageQueueAveragely();
new AllocateMachineRoomNearby(inner, resolver);

When it happens

Trigger: new AllocateMachineRoomNearby(null, resolver) — typically when the delegate strategy is injected via DI/framework config and the bean is missing or the field name is mistyped.

Common situations: Spring/XML bean wiring where the inner strategy bean id does not match the reference; programmatic setup where the delegate is conditionally created and the branch returned null.

Related errors

• machineRoomResolver is null
• illegal virtualNodeCnt :%d
• user can not be null
• currentCID is empty
• mqAll is null or mqAll empty

AI-assisted analysis of apache/rocketmq@293f588571 (2026-08-14). Data as JSON: /api/errors/eae08950ec650001. Report an issue: GitHub.