microsoft/garnet · error · TsavoriteException

ReadRecordObjects found no data available in ReadBuffers

Error message

ReadRecordObjects found no data available in ReadBuffers

What it means

Thrown by ObjectLogReader.ReadRecordObjects when readBuffers is non-null but OnBeginRecord returns false for the record's object-log position — the read-ahead window does not cover the requested record's position, or the buffers hold no data for it. The record references object-log bytes that the current buffered read does not contain.

Source

Thrown at libs/storage/Tsavorite/cs/src/core/Allocator/ObjectSerialization/ObjectLogReader.cs:104

        /// <param name="segmentSizeBits">Number of bits in segment size</param>
        /// <returns>False if requestedKey is set and we read an Overflow key and it did not match; otherwise true</returns>
        [MethodImpl(MethodImplOptions.NoInlining)]
        public bool ReadRecordObjects<TKey>(ref LogRecord logRecord, TKey requestedKey, int segmentSizeBits)
            where TKey : IKey
#if NET9_0_OR_GREATER
                , allows ref struct
#endif
        {
            Debug.Assert(logRecord.DataHeader.RecordHasObjects, "Inline records should have been checked by the caller");
            Debug.Assert(logRecord.HasReuseObjectIdForSize, "ReadRecordObjects requires the ReuseObjectIdForSize flag to be set on the ObjectLogPosition");
            if (readBuffers is null)
                throw new TsavoriteException("ReadBuffers are required to ReadRecordObjects");

            // R11 encoding: lengths returned by GetObjectLogRecordStartPositionAndLengths combine the RDH low bits with the next 32 bits
            // from the int* slot at keyAddress/valueAddress. No length prefix is in the object stream.
            var positionWord = logRecord.GetObjectLogRecordStartPositionAndLengths(out var keyLength, out var valueLength);
            if (!readBuffers.OnBeginRecord(new ObjectLogFilePositionInfo(positionWord, segmentSizeBits)))
                throw new TsavoriteException("ReadRecordObjects found no data available in ReadBuffers");

            // TODO: Optimize the reading of large internal sector-aligned parts of Overflow Keys and Values to read directly into the overflow, similar to how ObjectLogWriter writes
            //       directly from overflow. This requires changing the read-ahead in CircularDiskReadBuffer.OnBeginReadRecords and the "backfill" in CircularDiskReadBuffer.MoveToNextBuffer.

            // Note: Similar logic to this is in DiskLogRecord.Deserialize.
            var keyWasSet = false;
            try
            {
                if (logRecord.DataHeader.KeyIsOverflow)
                {
                    // This assignment also allocates the slot in ObjectIdMap, overwriting the int* slot at keyAddress
                    // (which held the high 32 bits of the on-disk key length per R11). The raw RDH KeyLength is restored
                    // to ObjectIdSize by OnObjectReadComplete below.
                    logRecord.KeyOverflow = new OverflowByteArray(keyLength, startOffset: 0, endOffset: 0, zeroInit: false);
                    _ = Read(logRecord.KeyOverflow.Span);
                    if (!requestedKey.IsEmpty && !storeFunctions.KeysEqual(requestedKey, logRecord))
                        return false;
                    keyWasSet = true;

View on GitHub (pinned to 951b0fc683)

Solutions

  1. Ensure OnBeginReadRecords is invoked with a filePosition/totalLength that covers the record before reading its objects (proper read-ahead setup).
  2. Increase the read-ahead window / NumberOfDeserializationBuffers so records stay buffered.
  3. Verify the record's object-log position word is within the segment currently loaded by the read buffer.

Example fix

// before
var ok = readBuffers.OnBeginRecord(new ObjectLogFilePositionInfo(positionWord, segmentSizeBits));
// after: set up read-ahead covering the record before OnBeginRecord
readBuffers.OnBeginReadRecords(filePosition, totalLength);
var ok = readBuffers.OnBeginRecord(new ObjectLogFilePositionInfo(positionWord, segmentSizeBits));
Defensive patterns

Strategy: validation

Validate before calling

// Ensure read-ahead covers the record before reading objects
readBuffers.OnBeginReadRecords(recordFilePosition, recordTotalLength);
if (!readBuffers.OnBeginRecord(new ObjectLogFilePositionInfo(positionWord, segmentSizeBits)))
    throw new InvalidOperationException("Read buffer does not cover this record's object-log position");

Try / catch

try { reader.ReadRecordObjects(ref logRecord, requestedKey, segmentSizeBits); }
catch (TsavoriteException ex) when (ex.Message.Contains("no data available in ReadBuffers"))
{
    logger.LogError(ex, "Read-ahead window missed the record; reposition buffers and retry");
    throw;
}

Prevention

When it happens

Trigger: Calling ReadRecordObjects for a record whose ObjectLogFilePositionInfo (from GetObjectLogRecordStartPositionAndLengths) falls outside what readBuffers.OnBeginReadRecords was set up for — e.g. read-ahead not advanced to this record, wrong segment, or a stale buffer position after recovery/seek.

Common situations: Read-ahead sizing too small for the record; the read buffer was positioned for a different record/segment; recovery copying where snapshot object reader wasn't demand-loaded for this range; a bug in buffer positioning leaving a gap.

Related errors

AI-assisted analysis of microsoft/garnet@951b0fc683 (2026-08-13). Data as JSON: /api/errors/3a6178d21851614a. Report an issue: GitHub.