LMAX-Exchange/disruptor · error · IllegalArgumentException

n must be > 0

Error message

n must be > 0

What it means

Thrown by SingleProducerSequencer.tryNext(int n) when n < 1. tryNext claims n slots non-blockingly and returns InsufficientCapacityException when the ring is full; only a non-positive claim is invalid input. Same validation as the multi-producer variant, for ProducerType.SINGLE ring buffers.

Source

Thrown at src/main/java/com/lmax/disruptor/SingleProducerSequencer.java:184

    /**
     * @see Sequencer#tryNext()
     */
    @Override
    public long tryNext() throws InsufficientCapacityException
    {
        return tryNext(1);
    }

    /**
     * @see Sequencer#tryNext(int)
     */
    @Override
    public long tryNext(final int n) throws InsufficientCapacityException
    {
        if (n < 1)
        {
            throw new IllegalArgumentException("n must be > 0");
        }

        if (!hasAvailableCapacity(n, true))
        {
            throw InsufficientCapacityException.INSTANCE;
        }

        long nextSequence = this.nextValue += n;

        return nextSequence;
    }

    /**
     * @see Sequencer#remainingCapacity()
     */
    @Override
    public long remainingCapacity()
    {

View on GitHub (pinned to c871ca4982)

Solutions

1. Break out of the claiming loop before calling tryNext with a count < 1.
2. Use the no-arg tryNext() for single-slot claims.
3. Test the loop's last iteration where remaining hits zero.

Example fix

// before
long seq = ringBuffer.tryNext(remaining); // remaining == 0

// after
if (remaining < 1) break;
long seq = ringBuffer.tryNext(remaining);

if (remaining >= 1) { long seq = ringBuffer.tryNext(remaining); /* ... */ }

When it happens

Trigger: Calling ringBuffer.tryNext(0) or tryNext(negative) on a single-producer ring — typically a claiming loop whose remaining count reaches 0 on the final iteration.

Common situations: Drain loop computes remaining = limit - claimed and calls tryNext(remaining) once too often; decrementing a shared count to 0 before the claim; batching math underflow.

Related errors

• n must be > 0
• n must be > 0 and < bufferSize
• n must be > 0 and < bufferSize
• maxBatchSize must be greater than 0
• Both batchStartsAt and batchSize must be positive but got: b

AI-assisted analysis of LMAX-Exchange/disruptor@c871ca4982 (2026-08-14). Data as JSON: /api/errors/ff5a3927f1744452. Report an issue: GitHub.