{"record":{"id":"07a66ad72c30ab83","repo":"MyCATApache/Mycat-Server","slug":"n-must-be-0-07a66a","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/SingleProducerSequencer.java","lineNumber":101,"sourceCode":"    @Override\n    public long remainingCapacity() {\n        //使用的 = 生产的 - 已经消费的\n        //剩余容量 = 容量 - 使用的\n        long nextValue = this.nextValue;\n        long consumed = Util.getMinimumSequence(gatingSequences, nextValue);\n        long produced = nextValue;\n        return getBufferSize() - (produced - consumed);\n    }\n\n    @Override\n    public long next() {\n        return next(1);\n    }\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 nextValue = this.nextValue;\n        //next方法和之前的hasAvailableCapacity同理，只不过这里是相当于阻塞的\n        long nextSequence = nextValue + n;\n        long wrapPoint = nextSequence - bufferSize;\n        long cachedGatingSequence = this.cachedValue;\n\n        if (wrapPoint > cachedGatingSequence || cachedGatingSequence > nextValue) {\n            long minSequence;\n            //只要wrapPoint大于最小的gatingSequences，那么不断唤醒消费者去消费，并利用LockSupport让出CPU，直到wrapPoint不大于最小的gatingSequences\n            while (wrapPoint > (minSequence = Util.getMinimumSequence(gatingSequences, nextValue))) {\n                waitStrategy.signalAllWhenBlocking();\n                LockSupport.parkNanos(1L); // TODO: Use waitStrategy to spin?\n            }\n            //同理，缓存最小的gatingSequences\n            this.cachedValue = minSequence;\n        }","sourceCodeStart":83,"sourceCodeEnd":119,"githubUrl":"https://github.com/MyCATApache/Mycat-Server/blob/65f8d8beb752f935752f2a0eec0ab017facab9ef/src/main/java/io/mycat/memory/unsafe/ringbuffer/producer/SingleProducerSequencer.java#L83-L119","documentation":"SingleProducerSequencer.next(n) is the blocking claim of n slots for the single publisher thread. It rejects n < 1 with IllegalArgumentException before computing the wrap point and waiting for consumers to free capacity.","triggerScenarios":"Calling next(0) or next(-1) (or RingBuffer.next(0)) on a single-producer ring buffer, typically from batch-publishing code whose chunk size computed to zero or negative.","commonSituations":"Publishing loops like while(remaining>0){ n=min(CHUNK,remaining); ... remaining-=n; } where rounding lets n become 0; empty event lists passed to a batch publisher.","solutions":["Skip the claim when the batch is empty instead of calling next(0)","Use next(1) for single-event publishes","Validate/chunk sizes so n is always >= 1"],"exampleFix":"// before\nlong seq = ringBuffer.next(events.size()); // 0 for empty list\n// after\nif (events.isEmpty()) return;\nlong seq = ringBuffer.next(events.size());","handlingStrategy":"validation","validationCode":"if (n >= 1) { long seq = ringBuffer.next(n); }","typeGuard":"boolean canClaim(int n) { return n >= 1; }","tryCatchPattern":"try { long seq = ringBuffer.next(n); } catch (IllegalArgumentException e) { log.error(\"invalid claim count\", e); }","preventionTips":["Use next(1) for single events","Guard batch loops against zero-size chunks","Early-return on empty event collections"],"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"}