hasura/graphql-engine · error · Error

Error while building the request for the pre-parse plugin {0

Error message

Error while building the request for the pre-parse plugin {0} - {1}

What it means

The pre-route plugin could not build the HTTP request to its hook — invalid URL or builder-rejected headers/body. The message says 'pre-parse plugin' (shared wording) but it originates in the pre-route executor; {1} carries the specific reason.

Source

Thrown at v3/crates/plugins/pre-route-plugin/src/execute.rs:24

};
use http_body_util::BodyExt;
use regex::Regex;
use serde::Serialize;

use open_dds::plugins::{
    LifecyclePreRoutePluginHook, LifecyclePreRoutePluginHookConfigRequestMethod,
    LifecyclePreRoutePluginHookIncomingHTTPMethod,
};
use serde_json::json;
use tracing_util::{
    ErrorVisibility, SpanVisibility, Traceable, TraceableError, set_attribute_on_active_span,
};

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("Error while making the HTTP request to the pre-parse plugin {0} - {1}")]
    ErrorWhileMakingHTTPRequestToTheHook(String, reqwest::Error),
    #[error("Error while building the request for the pre-parse plugin {0} - {1}")]
    BuildRequestError(String, String),
    #[error("Reqwest error: {0}")]
    ReqwestError(reqwest::Error),
    #[error("Unexpected status code: {0}")]
    UnexpectedStatusCode(u16),
    #[error("Error parsing the request: {0}")]
    PluginRequestParseError(serde_json::error::Error),
    #[error("HTTP method {0} not supported")]
    UnsupportedHTTPMethod(String),
    #[error("Invalid header name {0}")]
    InvalidHeaderName(String),
    #[error("Invalid header value {0}")]
    InvalidHeaderValue(String),
    #[error("Not found")]
    NotFound,
    // Only used in the pre-route plugin handler function. Defined to ensure consistent
    // response formatting in IntoResponse impl.
    #[error("Cannot load pre-route plugins: {0}")]

View on GitHub (pinned to 724551b9ae)

Solutions

1. Read the {1} field to see why the builder rejected the request.
2. Validate the URL at config load with url::Url::parse.
3. Trim/normalize env-provided URLs and headers.

Example fix

// before
let url = std::env::var("PRE_ROUTE_HOOK_URL")?;

// after
let url = std::env::var("PRE_ROUTE_HOOK_URL")?.trim().to_string();
url::Url::parse(&url)?;

let u = url::Url::parse(cfg.pre_route_hook_url.trim())?;
assert!(u.scheme().starts_with("http"));

When it happens

Trigger: Malformed hook URL for the pre-route plugin, or invalid header name/value being set when constructing the outgoing request.

Common situations: Config typo in the hook URL; env-substituted URL containing trailing whitespace/newline; dynamic headers with invalid characters.

Related errors

• Invalid header name {0}
• User error from plugin {plugin_name}
• Error while building the request for the pre-parse plugin {0
• Error while building the request for the pre-parse plugin {0
• Error while making the HTTP request to the pre-parse plugin

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/8c3e67cbfeeffadb. Report an issue: GitHub.