What causes "Failed to create default AxHttpClient" in nautechsystems/nautilus_trader?

Use AxHttpClient::new(...) explicitly and handle its Result instead of Default's expect.

nautechsystems/nautilus_trader · critical

Failed to create default AxHttpClient

Error message

Failed to create default AxHttpClient

What it means

AxHttpClient::default() calls new(None, None, 60, 3, 1000, 10_000, None) and expects success, panicking with 'Failed to create default AxHttpClient' if the underlying construction — default URL parsing and reqwest client building (which also constructs the raw client internally) — returns Err.

Source

Thrown at crates/adapters/architect_ax/src/http/client.rs:1162

    account_fees: Arc<ArcSwapOption<(Decimal, Decimal)>>,
}

impl Clone for AxHttpClient {
    fn clone(&self) -> Self {
        Self {
            inner: self.inner.clone(),
            instruments_cache: self.instruments_cache.clone(),
            cache_initialized: self.cache_initialized.clone(),
            clock: self.clock,
            account_fees: self.account_fees.clone(),
        }
    }
}

impl Default for AxHttpClient {
    fn default() -> Self {
        Self::new(None, None, 60, 3, 1000, 10_000, None)
            .expect("Failed to create default AxHttpClient")
    }
}

impl AxHttpClient {
    /// Creates a new [`AxHttpClient`] using the default Ax HTTP URL.
    ///
    /// # Errors
    ///
    /// Returns an error if the retry manager cannot be created.
    pub fn new(
        base_url: Option<String>,
        orders_base_url: Option<String>,
        timeout_secs: u64,
        max_retries: u32,
        retry_delay_ms: u64,
        retry_delay_max_ms: u64,
        proxy_url: Option<String>,
    ) -> Result<Self, AxHttpError> {

View on GitHub (pinned to 18893faf8b)

Solutions

Use AxHttpClient::new(...) explicitly and handle its Result instead of Default's expect.
Supply an explicit base URL and credentials through new() to rule out default-constant issues.
Verify reqwest TLS features (rustls vs native-tls) and that the binary links them correctly.
Confirm the default URL constant is still valid after upgrading the adapter crate.

Example fix

// before
let client = AxHttpClient::default(); // panics on failure
// after
let client = AxHttpClient::new(None, None, 60, 3, 1000, 10_000, None)?; // propagate the error

Defensive patterns

Strategy: try-catch

Validate before calling

// Ensure the default URL is parseable and TLS backend available before Default-based construction
assert!(url::Url::parse(DEFAULT_AX_HTTP_URL).is_ok(), "default AX URL invalid");

Try / catch

// Avoid Default()'s expect; construct explicitly and handle the error:
let client = AxHttpClient::new(None, None, 60, 3, 1000, 10_000, None)
    .map_err(|e| anyhow!("AxHttpClient init failed: {e}"))?;

Prevention

Use AxHttpClient::new with explicit arguments instead of Default in services.
Run a startup health check that constructs the client once before trading begins.
After adapter upgrades, re-verify the built-in default URL constant.

When it happens

Trigger: Calling AxHttpClient::default() when the built-in default AX HTTP URL fails to parse, or the internal reqwest/AxRawHttpClient construction fails (TLS/runtime initialization problems).

Common situations: Startup of the AX adapter in environments where reqwest's TLS backend cannot initialize; relying on Default in tests or binaries after an adapter version changed the default URL; miscompiled reqwest feature set.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/e2648f8aaa73e9ff. Report an issue: GitHub.