apache/cassandra · error · MarshalException

Not enough bytes to read value of component

Error message

Not enough bytes to read value of component 

What it means

During AbstractCompositeType.validate(), after reading a component's 2-byte size header the validator checks that `length` bytes are actually available. If fewer remain, MarshalException 'Not enough bytes to read value of component <i>' is thrown — the declared component length exceeds the remaining bytes, so the composite blob is truncated or the length header is wrong.

Source

Thrown at src/java/org/apache/cassandra/db/marshal/AbstractCompositeType.java:318

    public <V> void validate(V input, ValueAccessor<V> accessor)
    {
        boolean isStatic = readIsStatic(input, accessor);
        int offset = startingOffset(isStatic);

        int i = 0;
        V previous = null;
        while (!accessor.isEmptyFromOffset(input, offset))
        {
            AbstractType<?> comparator = validateComparator(i, input, accessor, offset);
            offset += getComparatorSize(i, input, accessor, offset);

            if (accessor.sizeFromOffset(input, offset) < 2)
                throw new MarshalException("Not enough bytes to read value size of component " + i);
            int length = accessor.getUnsignedShort(input, offset);
            offset += 2;

            if (accessor.sizeFromOffset(input, offset) < length)
                throw new MarshalException("Not enough bytes to read value of component " + i);
            V value = accessor.slice(input, offset, length);
            offset += length;

            comparator.validateCollectionMember(value, previous, accessor);

            if (accessor.isEmptyFromOffset(input, offset))
                throw new MarshalException("Not enough bytes to read the end-of-component byte of component" + i);
            byte b = accessor.getByte(input, offset++);
            if (b != 0 && !accessor.isEmptyFromOffset(input, offset))
                throw new MarshalException("Invalid bytes remaining after an end-of-component at component" + i);

            previous = value;
            ++i;
        }
    }

    @Override
    public void checkConstraints(ByteBuffer input, ColumnConstraints constraints) throws ConstraintViolationException

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Fix the serializer that writes the component length so it writes the exact value byte count as an unsigned short
2. Avoid round-tripping composite bytes through text encodings (Base64 or hex for transport instead)
3. Use the type's decompose()/build API rather than manual ByteBuffer assembly
4. Compare expected vs actual total byte length before submit: comparator sizes + sum(lengths+3)
5. Scrub/rebuild the table if stored sstable data is corrupt

Example fix

// before
bb.putShort((short) value.length);
bb.put(value, 0, value.length - 1); // wrong: one byte short
// after
bb.putShort((short) value.length);
bb.put(value);

// check every component's declared length fits before calling the API
int off = 0, i = 0;
while (off < buf.remaining()) {
    int hdr = /* comparator size */ 1;
    int len = ((buf.get(off + hdr) & 0xff) << 8) | (buf.get(off + hdr + 1) & 0xff);
    if (buf.remaining() < off + hdr + 2 + len)
        throw new IllegalArgumentException("Component " + i + " length " + len + " exceeds remaining bytes");
    off += hdr + 2 + len + 1; ++i;
}

try {
    type.validate(bytes);
} catch (MarshalException e) {
    if (e.getMessage().startsWith("Not enough bytes to read value of component"))
        logger.error("Composite length header corrupt — reserialize with decompose()");
    else throw e;
}

When it happens

Trigger: Validating a serialized composite where a component advertises (via its unsigned-short length) more bytes than remain in the buffer — typical of hand-built composites with incorrect length fields or truncated byte arrays.

Common situations: Off-by-one or wrong-endian length writing in custom code building composite keys; truncation when copying values through string/UTF-8 conversions; import/export tools mangling binary values; corrupted stored values.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Not enough bytes to read value size of component
• Not enough bytes to read the end-of-component byte of compon
• Invalid bytes remaining after an end-of-component at compone
• Invalid byte for ascii: + Byte.toString(b)
• Expected 1 or 0 byte value (%d)

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/b54101ef95149027. Report an issue: GitHub.