{"record":{"id":"8425b0e741de0e6a","repo":"MyCATApache/Mycat-Server","slug":"n-must-be-0","errorCode":null,"errorMessage":"n must be > 0","messagePattern":"n must be > 0","errorType":"validation","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"src/main/java/io/mycat/memory/unsafe/ringbuffer/producer/MultiProducerSequencer.java","lineNumber":183,"sourceCode":"        long produced = cursor.get();\n        return getBufferSize() - (produced - consumed);\n    }\n\n    @Override\n    public long next() {\n        return next(1);\n    }\n\n    /**\n     * 用于多个生产者抢占n个RingBuffer槽用于生产Event\n     *\n     * @param n\n     * @return\n     */\n    @Override\n    public long next(int n) {\n        if (n < 1) {\n            throw new IllegalArgumentException(\"n must be > 0\");\n        }\n\n        long current;\n        long next;\n\n        do {\n            //首先通过缓存判断空间是否足够\n            current = cursor.get();\n            next = current + n;\n\n            long wrapPoint = next - bufferSize;\n            long cachedGatingSequence = gatingSequenceCache.get();\n            //如果缓存不满足\n            if (wrapPoint > cachedGatingSequence || cachedGatingSequence > current) {\n                //重新获取最小的\n                long gatingSequence = Util.getMinimumSequence(gatingSequences, current);\n                //如果空间不足，则唤醒消费者消费，并让出CPU\n                if (wrapPoint > gatingSequence) {","sourceCodeStart":165,"sourceCodeEnd":201,"githubUrl":"https://github.com/MyCATApache/Mycat-Server/blob/65f8d8beb752f935752f2a0eec0ab017facab9ef/src/main/java/io/mycat/memory/unsafe/ringbuffer/producer/MultiProducerSequencer.java#L165-L201","documentation":"MultiProducerSequencer.next(n) claims n consecutive sequences for a publisher. It validates n >= 1 and throws IllegalArgumentException for n < 1, since claiming zero or a negative number of slots is meaningless. This is the blocking claim path; the argument check happens before any spinning on the gating sequences.","triggerScenarios":"Calling sequencer.next(0) or next(-1) (or RingBuffer.next(0)) directly, or via a batch publisher whose batchSize was computed as 0 or negative (e.g. empty-batch subtraction).","commonSituations":"Batching logic computing batchSize = end - start when end == start; config where minBatchSize defaults to 0; off-by-one in loop that publishes in chunks.","solutions":["Only call next() with n >= 1; skip the call entirely for empty batches","Clamp the requested count: Math.max(1, n) if a claim is always required","Fix the batch computation so batchSize reflects the actual number of events to publish"],"exampleFix":"// before\nint batchSize = endIndex - startIndex;\nlong seq = sequencer.next(batchSize);\n// after\nint batchSize = endIndex - startIndex;\nif (batchSize <= 0) return;\nlong seq = sequencer.next(batchSize);","handlingStrategy":"validation","validationCode":"if (n >= 1) { long seq = sequencer.next(n); }","typeGuard":"boolean canClaim(int n) { return n >= 1; }","tryCatchPattern":"try { long seq = sequencer.next(n); } catch (IllegalArgumentException e) { log.error(\"invalid claim count\", e); }","preventionTips":["Early-return from batch publish when the batch is empty","Never derive claim counts from unchecked arithmetic","Clamp chunk sizes to at least 1"],"tags":["java","ringbuffer","argument-validation"],"backgroundTag":"invalid-argument-value","analyzedSha":"65f8d8beb752f935752f2a0eec0ab017facab9ef","analyzedAt":"2026-09-11T00:12:21.696Z","contentChangedAt":"2026-09-11T00:12:21.696Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}