nautechsystems/nautilus_trader · error

{description} endpoint host is required

Error message

{description} endpoint host is required

What it means

Thrown by `validate_execution_endpoint` when the parsed URL has no host component. An HTTP JSON-RPC endpoint must address a host, so scheme-only or opaque URLs (e.g. `http:` with nothing after it, or `mailto:`-like forms) fail this check.

Source

Thrown at crates/adapters/blockchain/src/rpc/http.rs:922

            .ok_or_else(|| BroadcastError::Failed("Broadcast returned no result".to_string()))?;

        B256::from_str(&hex_string)
            .map_err(|e| BroadcastError::Failed(format!("Failed to parse broadcast result: {e}")))
    }
}

#[cfg(feature = "hypersync")]
pub(crate) fn validate_execution_endpoint(
    endpoint: &str,
    description: &str,
) -> anyhow::Result<Url> {
    let url =
        Url::parse(endpoint).map_err(|_| anyhow::anyhow!("Invalid {description} endpoint"))?;
    anyhow::ensure!(
        matches!(url.scheme(), "http" | "https"),
        "{description} endpoint must use HTTPS or canonical loopback HTTP"
    );
    anyhow::ensure!(
        url.host().is_some(),
        "{description} endpoint host is required"
    );
    anyhow::ensure!(
        url.fragment().is_none(),
        "{description} endpoint fragments are unsupported"
    );
    anyhow::ensure!(
        url.scheme() == "https" || is_canonical_loopback_endpoint(endpoint),
        "{description} endpoint must use HTTPS unless its host is a canonical loopback IP literal"
    );
    Ok(url)
}

fn is_canonical_loopback_endpoint(endpoint: &str) -> bool {
    let Some((scheme, rest)) = endpoint.split_once("://") else {
        return false;
    };

View on GitHub (pinned to 18893faf8b)

Solutions

1. Ensure the configured value includes a host: `https://your-node.example.com:8545`.
2. Check that environment variable/templating substitution actually populated the host part.
3. Validate the endpoint string at startup (fail fast) rather than at first RPC call.

Example fix

// before
let endpoint = &format!("https://{}", std::env::var("RPC_HOST").unwrap_or_default()); // empty host
// after
let endpoint = &format!("https://{}", std::env::var("RPC_HOST").expect("RPC_HOST must be set"));

let url = url::Url::parse(endpoint)?;
anyhow::ensure!(url.host().is_some(), "endpoint is missing a host: '{endpoint}'");

fn has_host(s: &str) -> bool {
    url::Url::parse(s).map(|u| u.host().is_some()).unwrap_or(false)
}

let endpoint = format!("https://{}", host_var); // ensure substitution happened
let client = HttpRpcClient::new(&endpoint).map_err(|e| {
    if e.to_string().contains("host is required") {
        anyhow::anyhow!("RPC_HOST is unset or empty; got endpoint '{endpoint}'")
    } else { e.into() }
})?;

When it happens

Trigger: Passing a URL that parses but yields `url.host() == None` — e.g. `"http://"`, `"https:///path"`, or a scheme-only string — to `new`, `normalize_endpoint`, or validation tests.

Common situations: Config value partially deleted leaving `http://` behind; templating variable left empty so the URL becomes `https://${HOST}` with HOST unset; string concatenation bugs building the endpoint.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

Related errors

• Invalid {description} endpoint
• {description} endpoint must use HTTPS or canonical loopback
• {description} endpoint fragments are unsupported
• request_rate_per_second must be greater than zero
• order_request_rate_per_second must be greater than zero

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/e72c265b422847fa. Report an issue: GitHub.