databendlabs/databend · error

Lua execution error

Error message

Lua execution error: {}

What it means

run_lua_script executes a Lua script on an mlua async runtime. If `lua.load(script).exec_async()` returns Err — a syntax error, a runtime error raised by the script (via `error()`), or a callback error — the function wraps it in anyhow with "Lua execution error: {}". This is a pass-through wrapper: the real cause is in the inner Lua error message.

Solutions

1. Read the inner Lua error after 'Lua execution error:' to find the failing line/function in the script
2. Validate the script syntax with a standalone lua interpreter (luac -p) before running it against meta
3. Fix the nil reference or error() call inside the Lua script
4. If a Rust callback is the cause, fix that function's error condition

Example fix

// before: run script directly and get opaque failure
run_lua_script(&script).await?;
// after: smoke-test compile first (in a test)
let lua = mlua::Lua::new();
lua.load(&script).exec_async().await
    .expect("script must compile and run");

if let Err(e) = luac_check(&script) { bail!("script will not compile: {e}"); }

fn is_compilable_lua(script: &str) -> bool { luac_syntax_check(script).is_ok() }

match run_lua_script(&script).await {
    Ok(()) => {},
    Err(e) if e.to_string().contains("Lua execution error") => log::error!("lua script failed: {e:#}"),
    Err(e) => return Err(e),
}

When it happens

Trigger: Calling run_lua_script(script) where the script fails to compile (syntax error), calls error()/panic, references a nil global, or a Rust-registered function it calls returns an error.

Common situations: Meta-service Lua maintenance/upgrade scripts edited by hand with typos; scripts assuming tables or APIs that don't exist in the embedded runtime; scripts that raise errors on unexpected meta data state.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Unsupported format for
• Unsupported source type. Expected path, pandas.DataFrame…
• Access denied: is outside allowed directories
• rename_database: src (db) should exist
• internal error: expect TxnGetResponseGet of get database…

AI-assisted analysis of databendlabs/databend@288d84d76e (2026-09-11). Data as JSON: /api/errors/95f3418cea02221a. Report an issue: GitHub.

Appendix: source

Thrown at src/meta/control/src/lua_support.rs:533

        DEFAULT_GRPC_MESSAGE_SIZE,
    )
}

pub fn new_admin_client(addr: &str) -> MetaAdminClient {
    MetaAdminClient::new(addr)
}

pub async fn run_lua_script(script: &str) -> anyhow::Result<()> {
    let lua = Lua::new();

    setup_lua_environment(&lua)?;

    #[allow(clippy::disallowed_types)]
    let local = tokio::task::LocalSet::new();
    let res = local.run_until(lua.load(script).exec_async()).await;

    if let Err(e) = res {
        return Err(anyhow::anyhow!("Lua execution error: {}", e));
    }
    Ok(())
}

pub async fn run_lua_script_with_result(
    script: &str,
) -> anyhow::Result<Result<Option<String>, String>> {
    let lua = Lua::new();

    setup_lua_environment(&lua)?;

    #[allow(clippy::disallowed_types)]
    let local = tokio::task::LocalSet::new();
    let res = local
        .run_until(lua.load(script).eval_async::<mlua::MultiValue>())
        .await;

    match res {

View on GitHub (pinned to 288d84d76e)