apache/cassandra · error · IllegalStateException

output buffer is not large enough for data: current capacity

Error message

output buffer is not large enough for data: current capacity %d, required %d

What it means

IllegalArgumentException from ByteBufferUtil.ensureCapacity when the existing buffer's capacity is below the required outputLength and buffer resizing is not allowed (allowBufferResize false). The caller demanded in-place capacity that the buffer cannot provide, so the operation fails rather than leaking/replacing the buffer.

Solutions

1. Set allowBufferResize=true if the caller permits reallocation
2. Pre-size the buffer to the maximum possible output (e.g., compressor.maxCompressedLength(input))
3. Use input size plus a safety margin for worst-case compression expansion
4. Pool buffers keyed by size class so capacity always matches

Example fix

// before
buf = ByteBufferUtil.ensureCapacity(buf, needed, false, BufferType.OFF_HEAP);
// after
int max = compressor.maxCompressedLength(inputLength);
if (buf == null || buf.capacity() < max)
    buf = BufferType.OFF_HEAP.allocate(max);
buf = ByteBufferUtil.ensureCapacity(buf, needed, true, BufferType.OFF_HEAP);

// pre-size buffer to worst case
int required = compressor.maxCompressedLength(inputLength);
if (buf == null || buf.capacity() < required)
    buf = bufferType.allocate(required);

try {
    buf = ByteBufferUtil.ensureCapacity(buf, outputLength, false, bufferType);
} catch (IllegalStateException e) {
    // parse 'required %d' from message and reallocate
}

When it happens

Trigger: Calling ensureCapacity (via compression/checksum paths such as ICompressor) with a caller-owned buffer too small for the output and resizing explicitly disallowed.

Common situations: Pre-allocated buffer sized from a stale/incorrect max-chunk estimate; buffer reused across differing compression ratios; off-heap buffer too small for worst-case compression expansion.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

• Access forbidden
• Cannot access method create in
• Cannot convert value
• Cannot create CompressionParams for stored parameters
• Cannot initialize class

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/c662a01bdff55c61. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/utils/ByteBufferUtil.java:918

    /**
     * Ensure {@code buf} is large enough for {@code outputLength}. If not, it is cleaned up and a new buffer is allocated;
     * else; buffer has it's position/limit set appropriately.
     *
     * @param buf buffer to test the size of; may be null, in which case, a new buffer is allocated.
     * @param outputLength the minimum target size of the buffer
     * @param allowBufferResize true if resizing (reallocating) the buffer is allowed
     * @param bufferType on- or off- heap byte buffer
     * @return {@code buf} if it was large enough, else a newly allocated buffer.
     */
    public static ByteBuffer ensureCapacity(ByteBuffer buf, int outputLength, boolean allowBufferResize, BufferType bufferType)
    {
        if (0 > outputLength)
            throw new IllegalArgumentException("invalid size for output buffer: " + outputLength);
        if (buf == null || buf.capacity() < outputLength)
        {
            if (!allowBufferResize)
                throw new IllegalStateException(String.format("output buffer is not large enough for data: current capacity %d, required %d", buf.capacity(), outputLength));
            MemoryUtil.clean(buf);
            buf = bufferType.allocate(outputLength);
        }
        else
        {
            buf.position(0).limit(outputLength);
        }
        return buf;
    }

    /**
     * Check is the given buffer contains a given sub-buffer.
     *
     * @param buffer The buffer to search for sequence of bytes in.
     * @param subBuffer The buffer to match.
     *
     * @return true if buffer contains sub-buffer, false otherwise.
     */

View on GitHub (pinned to 88fd0f6a0e)