firecracker-microvm/firecracker · error

'http-api-max-payload-size' parameter expected to be of 'usi

Error message

'http-api-max-payload-size' parameter expected to be of 'usize' type.

What it means

Error "'http-api-max-payload-size' parameter expected to be of 'usize' type." thrown in firecracker-microvm/firecracker.

Source

Thrown at src/firecracker/src/main.rs:405

    let vmm_config_json = arguments
        .single_value("config-file")
        .map(fs::read_to_string)
        .map(|x| x.expect("Unable to open or read from the configuration file"));

    let metadata_json = arguments
        .single_value(MMDS_CONTENT_ARG)
        .map(fs::read_to_string)
        .map(|x| x.expect("Unable to open or read from the mmds content file"));

    let boot_timer_enabled = arguments.flag_present("boot-timer");
    let pci_enabled = arguments.flag_present("enable-pci");
    let api_enabled = !arguments.flag_present("no-api");
    let api_payload_limit = arg_parser
        .arguments()
        .single_value("http-api-max-payload-size")
        .map(|lim| {
            lim.parse::<usize>()
                .expect("'http-api-max-payload-size' parameter expected to be of 'usize' type.")
        })
        // Safe to unwrap as we provide a default value.
        .unwrap();

    // If the mmds size limit is not explicitly configured, default to using the
    // `http-api-max-payload-size` value.
    let mmds_size_limit = arg_parser
        .arguments()
        .single_value("mmds-size-limit")
        .map(|lim| {
            lim.parse::<usize>()
                .expect("'mmds-size-limit' parameter expected to be of 'usize' type.")
        })
        .unwrap_or_else(|| api_payload_limit);

    if api_enabled {
        let bind_path = arguments
            .single_value("api-sock")

View on GitHub (pinned to 0a745def42)

Solutions

1. Pass a non-negative integer for the http-api-max-payload-size metadata value.
2. Check the config file JSON types; the value must be a number, not a string.

When it happens

Trigger: Thrown at src/firecracker/src/main.rs:405 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of firecracker-microvm/firecracker@0a745def42 (2026-08-19). Data as JSON: /api/errors/1e33ab4ae677ba33. Report an issue: GitHub.