microsoft/garnet · error · GarnetException

Internal Lua Error: {res}

Error message

Internal Lua Error: {res}

What it means

Thrown by CompileForRunner when the protected compile call returned a non-OK LuaStatus (res) and the runner produced no RESP error frame. Unlike the RESP-error case, there is no friendly text - only the raw LuaStatus enum value. This indicates the Lua VM itself misbehaved during compilation rather than reporting a normal script error.

Source

Thrown at libs/server/Lua/LuaRunner.cs:444

            try
            {
                LuaRunnerTrampolines.SetCallbackContext(this);
                state.PushCFunction(&LuaRunnerTrampolines.CompileForRunner);
                var res = state.PCall(0, 0);
                if (res == LuaStatus.OK)
                {
                    var resp = runnerAdapter.Response;
                    var respStart = (byte*)Unsafe.AsPointer(ref MemoryMarshal.GetReference(resp));
                    var respEnd = respStart + resp.Length;
                    if (RespReadUtils.TryReadErrorAsSpan(out var errSpan, ref respStart, respEnd))
                    {
                        var errStr = Encoding.UTF8.GetString(errSpan);
                        throw new GarnetException(errStr);
                    }
                }
                else
                {
                    throw new GarnetException($"Internal Lua Error: {res}");
                }
            }
            finally
            {
                runnerAdapter = default;
                LuaRunnerTrampolines.ClearCallbackContext(this);
            }
        }

        /// <summary>
        /// Compile script for a <see cref="RespServerSession"/>.
        /// 
        /// Any errors encountered are written out as Resp errors.
        /// </summary>
        public unsafe bool CompileForSession(RespServerSession session)
        {
            state.ExpectLuaStackEmpty();

View on GitHub (pinned to 951b0fc683)

Solutions

1. Inspect the LuaStatus value (res) in the logs to map it to a Lua error class (e.g., ERRMEM, ERRERR).
2. Check memory pressure and configured memory limits on the Lua/runner.
3. Recreate the Lua state / restart the session; if reproducible, file it as an internal bug with the script that triggered it.

catch (GarnetException ex) when (ex.Message.StartsWith("Internal Lua Error")) {
    logger.LogError("Lua PCall returned non-OK status during compile: {Msg}", ex.Message);
    throw; // typically non-recoverable for this state; report and restart session
}

When it happens

Trigger: state.PCall for compilation returns a non-OK status and the runner adapter's response buffer did not contain a parseable RESP error, so the code falls to the else branch and throws 'Internal Lua Error: {res}'.

Common situations: Out-of-memory inside the Lua VM; stack overflow; a corrupted Lua state; a build mismatch. Rare under normal load.

Related errors

• Could not initialize Lua VM: {innerError}
• Could not initialize Lua VM
• Could not initialize Lua sandbox state: {errMsg}
• {errStr}
• Could not run function preamble: {errMsg}

AI-assisted analysis of microsoft/garnet@951b0fc683 (2026-08-13). Data as JSON: /api/errors/69eb4419627c652d. Report an issue: GitHub.