influxdata/influxdb · error · Error

failed to build an http client

Error message

failed to build an http client: {}

What it means

Error::Builder, raised during Client construction when reqwest's ClientBuilder fails to produce an HTTP client. The reqwest::Error is attached as #[source] and described via reqwest_description. This happens once, before any request is made, and always indicates a problem with the client configuration, not the server.

Solutions

1. Unwrap the source chain to see which builder option reqwest rejected
2. Validate the CA certificate file exists and contains valid PEM before passing it to add_root_certificate
3. Simplify the builder config (remove custom certs/TLS options) to isolate the failing option
4. Ensure the TLS backend dependency is properly installed (openssl/pkg-config on the build host)
5. Rebuild the client with a plain reqwest::Client::new() to confirm the base builder works in the environment

Example fix

// before
let ca = Certificate::from_pem(std::fs::read("ca.pem")?); // invalid/missing PEM
let client = Client::new(url, token, Some(ca), ...)?; // Builder error
// after
let pem = std::fs::read("ca.pem")?;
let ca = Certificate::from_pem(&pem)?; // validate early
let client = Client::new(url, token, Some(ca), ...)?;

// validate cert material before building the client
fn validate_pem(path: &std::path::Path) -> Result<(), String> {
    let data = std::fs::read(path).map_err(|e| e.to_string())?;
    if !data.starts_with(b"-----BEGIN ") { return Err("not a PEM file".into()); }
    reqwest::Certificate::from_pem(&data).map(|_| ()).map_err(|e| e.to_string())
}

fn is_builder_error(e: &influxdb3_client::Error) -> bool {
    matches!(e, influxdb3_client::Error::Builder(_))
}

let client = match Client::new(url, token, ca, ...) {
    Err(e @ influxdb3_client::Error::Builder(src)) => {
        eprintln!("client config invalid: {src:#}");
        return Err(e); // fail fast at startup, never retry
    }
    other => other?,
};

When it happens

Trigger: Building the Client with invalid TLS configuration: unreadable/invalid CA certificate passed to add_root_certificate, invalid TLS version constraints, conflicting or invalid builder options (e.g. bad timeout values), or failure initializing the TLS backend.

Common situations: Pointing the client at a CA bundle path that doesn't exist or contains invalid PEM; enabling mutual TLS with a malformed client cert/key; platform TLS backend initialization failures (missing OpenSSL, restricted FIPS environments).

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• failed to parse JSON response
• failed to parse plaintext response
• failed to send request
• tls config error
• base URL error

AI-assisted analysis of influxdata/influxdb@06200ef96b (2026-09-19). Data as JSON: /api/errors/2da9a6a259afa88b. Report an issue: GitHub.

Appendix: source

Thrown at influxdb3_client/src/lib.rs:72

    Text(#[source] reqwest::Error),

    #[error("server responded with error [{code}]: {message}")]
    ApiError {
        code: StatusCode,
        message: String,
        /// Machine-readable error code from JSON error responses, if present.
        error_code: Option<String>,
    },

    #[error("failed to send {method} {url} request: {}", reqwest_description(.source))]
    RequestSend {
        method: Method,
        url: String,
        #[source]
        source: reqwest::Error,
    },

    #[error("failed to build an http client: {}", reqwest_description(.0))]
    Builder(#[source] reqwest::Error),

    #[error("io error: {0}")]
    IO(#[from] std::io::Error),
}

/// Try to parse a JSON error response body with `error_code` and `message` fields.
/// Returns `(message, error_code)`. If JSON parsing fails, treats the body as plain text.
pub(crate) fn parse_error_body(body: &str) -> (String, Option<String>) {
    #[derive(serde::Deserialize)]
    struct JsonError {
        #[serde(default)]
        error_code: Option<String>,
        #[serde(default)]
        message: Option<String>,
    }
    if let Ok(parsed) = serde_json::from_str::<JsonError>(body) {
        let message = parsed.message.unwrap_or_else(|| body.to_string());

View on GitHub (pinned to 06200ef96b)