databendlabs/databend · error

Failed to register metactl namespace

Error message

Failed to register metactl namespace: {}

What it means

After all members are registered, the `metactl` table itself is assigned as a global with `lua.globals().set("metactl", metactl_table)`. If mlua fails to store the table into the globals table, the error is wrapped as `Failed to register metactl namespace` and setup aborts.

Solutions

1. Inspect the inner mlua error; memory/stack errors mean the Lua instance should be recreated.
2. Check that no earlier script enabled a sandbox/readonly-globals mode that blocks `globals().set`.
3. Ensure `metactl_table` was created in the same Lua instance whose globals are being set.
4. Increase or drop custom MemoryLimits; if still failing, report the inner error against mlua.

match setup_lua_environment(&lua) {
    Err(e) if e.to_string().contains("Failed to register metactl namespace") => {
        // sandbox/globals or state problem: rebuild environment
    }
    other => other?,
}

When it happens

Trigger: `lua.globals().set("metactl", metactl_table)` returning an mlua error during `setup_lua_environment`, before `LUA_UTIL` is loaded.

Common situations: Lua stack/memory exhaustion, a globals table that has been locked or replaced by sandboxing code, or values from a mismatched Lua instance.

Related errors

• Failed to create now_ms function
• Failed to create sleep function
• Failed to create spawn function
• Failed to register now_ms function
• Failed to register sleep function

AI-assisted analysis of databendlabs/databend@288d84d76e (2026-09-11). Data as JSON: /api/errors/f02430f483d0fa86. Report an issue: GitHub.

Appendix: source

Thrown at src/meta/control/src/lua_support.rs:491

        .set("now_ms", now_ms_fn)
        .map_err(|e| anyhow::anyhow!("Failed to register now_ms function: {}", e))?;

    // Register the Zipf load generator. The module returns the `ZipfGenerator`
    // table, exposed as `metactl.ZipfGenerator` so any script can call
    // `metactl.ZipfGenerator:new(num_keys, alpha)` directly.
    let zipf_generator = lua
        .load(ZIPF_LOAD_GENERATOR)
        .eval::<Table>()
        .map_err(|e| anyhow::anyhow!("Failed to load zipf_load_generator: {}", e))?;

    metactl_table
        .set("ZipfGenerator", zipf_generator)
        .map_err(|e| anyhow::anyhow!("Failed to register ZipfGenerator: {}", e))?;

    // Set the metactl table as a global
    lua.globals()
        .set("metactl", metactl_table)
        .map_err(|e| anyhow::anyhow!("Failed to register metactl namespace: {}", e))?;

    // Load lua_util functions (which registers to_string in metactl namespace)
    lua.load(LUA_UTIL)
        .exec()
        .map_err(|e| anyhow::anyhow!("Failed to load lua_util functions: {}", e))?;

    Ok(())
}

pub fn new_grpc_client(
    addresses: Vec<String>,
) -> Result<Arc<ClientHandle<DatabendRuntime>>, CreationError> {
    eprintln!(
        "Using gRPC API address: {}",
        serde_json::to_string(&addresses).unwrap()
    );
    MetaGrpcClient::try_create(
        addresses,

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