MyCATApache/Mycat-Server · error · IllegalArgumentException

A batchSize of: with batchStatsAt of: will overrun the…

Error message

A batchSize of: ${batchSize} with batchStatsAt of: ${batchStartsAt} will overrun the available number of arguments: ${available}

What it means

batchOverRuns verifies that a batch publish request does not ask for more translator arguments than the supplied argument array actually holds. When batchStartsAt + batchSize exceeds arg0.length, the call would read past the end of the array, so IllegalArgumentException is thrown with the remaining argument count in the message.

Solutions

1. Clamp batchSize to translators.length - batchStartsAt before the call.
2. Verify batchStartsAt is the intended offset and that the array contains all expected elements.
3. Pass the full array with batchStartsAt=0 and batchSize=translators.length when publishing everything.
4. Add an assertion/unit test covering the offset+size arithmetic.

Example fix

// before
ring.publishEvents(translators, 5, 8); // overrun
// after
int start = 5;
int size = Math.min(8, translators.length - start);
ring.publishEvents(translators, start, size);

public static void checkBatch(Object[] args, int batchStartsAt, int batchSize) {
    if (batchStartsAt < 0 || batchSize < 0 || batchStartsAt + batchSize > args.length)
        throw new IllegalArgumentException("batch out of bounds: start=" + batchStartsAt + " size=" + batchSize + " len=" + args.length);
}

try {
    ring.publishEvents(translators, start, size);
} catch (IllegalArgumentException e) {
    logger.warn("batch overrun, clamping", e);
    ring.publishEvents(translators, start, translators.length - start);
}

When it happens

Trigger: Calling RingBuffer batch publish APIs (e.g. publishEvents(translators, batchStartsAt, batchSize)) where batchStartsAt + batchSize > translators.length, e.g. 10 translators with batchStartsAt=5, batchSize=8.

Common situations: Off-by-one errors when slicing an array of event translators, computing batchSize from a list size but a different offset, or reusing a batch size constant after changing array contents.

Related errors

• Both batchStartsAt and batchSize must be positive but got…
• The ring buffer cannot accommodate
• bufferSize must not be less than 1
• bufferSize must be a power of 2
• bufferSize must not be less than 1

AI-assisted analysis of MyCATApache/Mycat-Server@65f8d8beb7 (2026-09-11). Data as JSON: /api/errors/2d937b4f989e8648. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/io/mycat/memory/unsafe/ringbuffer/RingBuffer.java:270

    @Override
    public boolean tryPublishEvent(EventTranslatorVararg<E> translator, Object... args) {
        try {
            final long sequence = sequencer.tryNext();
            translateAndPublish(translator, sequence, args);
            return true;
        } catch (InsufficientCapacityException e) {
            return false;
        }
    }

    private void checkBounds(final EventTranslator<E>[] translators, final int batchStartsAt, final int batchSize) {
        checkBatchSizing(batchStartsAt, batchSize);
        batchOverRuns(translators, batchStartsAt, batchSize);
    }

    private <A> void batchOverRuns(final A[] arg0, final int batchStartsAt, final int batchSize) {
        if (batchStartsAt + batchSize > arg0.length) {
            throw new IllegalArgumentException(
                    "A batchSize of: " + batchSize +
                            " with batchStatsAt of: " + batchStartsAt +
                            " will overrun the available number of arguments: " + (arg0.length - batchStartsAt));
        }
    }

    private void checkBatchSizing(int batchStartsAt, int batchSize) {
        if (batchStartsAt < 0 || batchSize < 0) {
            throw new IllegalArgumentException("Both batchStartsAt and batchSize must be positive but got: batchStartsAt " + batchStartsAt + " and batchSize " + batchSize);
        } else if (batchSize > bufferSize) {
            throw new IllegalArgumentException("The ring buffer cannot accommodate " + batchSize + " it only has space for " + bufferSize + " entities.");
        }
    }

    /**
     * @see io.mycat.memory.unsafe.ringbuffer.common.event.EventSink#publishEvent(EventTranslator)
     */
    @Override

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