apache/cassandra · error · IllegalStateException

Insufficient remaining bytes to deserialize Inner node…

Error message

Insufficient remaining bytes to deserialize Inner node off-heap

What it means

MerkleTree.Inner.serializeOffHeap writes an off-heap representation of an inner node into a caller-provided ByteBuffer. Before writing it verifies the buffer has at least maxOffHeapSize(partitioner) bytes remaining; if not it throws this IllegalStateException. The message says 'deserialize' but is thrown on the serialize path — it is a buffer-capacity guard against truncating a node mid-write.

Solutions

1. Size the destination ByteBuffer to at least OffHeapInner.maxOffHeapSize(partitioner) before calling serializeOffHeap
2. Recompute buffer size with the current partitioner's token factory byte size; do not cache sizes across partitioner changes
3. Check buffer.remaining() / ensure the buffer position is reset (clear/rewind) before serializing
4. Inspect call sites that write multiple nodes into one buffer and make sure each node's space is reserved

Example fix

// before
ByteBuffer buf = ByteBuffer.allocate(128);
inner.serializeOffHeap(buf, partitioner);
// after
ByteBuffer buf = ByteBuffer.allocate(OffHeapInner.maxOffHeapSize(partitioner));
inner.serializeOffHeap(buf, partitioner);

if (buffer.remaining() < OffHeapInner.maxOffHeapSize(partitioner)) throw new IllegalStateException("buffer too small for inner node");

try { inner.serializeOffHeap(buffer, partitioner); } catch (IllegalStateException e) { /* resize buffer to maxOffHeapSize(partitioner) and retry */ }

When it happens

Trigger: Calling Inner.serializeOffHeap with a ByteBuffer whose remaining() is smaller than OffHeapInner.maxOffHeapSize(partitioner), typically when the buffer was sized without accounting for the token size or the short/long header fields, or when the buffer was partially consumed before the call.

Common situations: Anti-entropy/repair code serializing merkle trees into fixed-size buffers after the partitioner was changed (e.g. RandomPartitioner vs Murmur3 token sizes), or hand-rolled buffer sizing that underestimates token byte size.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• Failed to serialize partition key
• Hash of size encountered, expecting or
• Unexpected node type: " + ident
• Attempted to encode a response with an unset stream id:
• Cannot convert value

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/03939c7396773be1. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/utils/MerkleTree.java:1328

                computed = true;
            }

            return this;
        }

        static OnHeapInner deserializeWithoutIdent(DataInputPlus in, IPartitioner p, int version) throws IOException
        {
            Token token = Token.serializer.deserialize(in, p, version);
            OnHeapNode  left = OnHeapNode.deserialize(in, p, version);
            OnHeapNode right = OnHeapNode.deserialize(in, p, version);
            return new OnHeapInner(token, left, right);
        }

        int serializeOffHeap(ByteBuffer buffer, IPartitioner partitioner) throws IOException
        {
            if (buffer.remaining() < OffHeapInner.maxOffHeapSize(partitioner))
                throw new IllegalStateException("Insufficient remaining bytes to deserialize Inner node off-heap");

            final int offset = buffer.position();

            int tokenSize = partitioner.getTokenFactory().byteSize(token);
            buffer.putShort(offset + OffHeapInner.TOKEN_LENGTH_OFFSET, Shorts.checkedCast(tokenSize));
            buffer.position(offset + OffHeapInner.TOKEN_BYTES_OFFSET);
            partitioner.getTokenFactory().serialize(token, buffer);

            int  leftPointer =  left.serializeOffHeap(buffer, partitioner);
            int rightPointer = right.serializeOffHeap(buffer, partitioner);

            buffer.putInt(offset + OffHeapInner.LEFT_CHILD_POINTER_OFFSET,  leftPointer);
            buffer.putInt(offset + OffHeapInner.RIGHT_CHILD_POINTER_OFFSET, rightPointer);

            int  leftHashOffset = OffHeapInner.hashBytesOffset(leftPointer);
            int rightHashOffset = OffHeapInner.hashBytesOffset(rightPointer);

            for (int i = 0; i < HASH_SIZE; i += 8)

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