lmn-core 0.3.0

Core engine for the lmn HTTP load testing CLI
Documentation 
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use std::sync::Arc;
use std::time::Duration;
use std::time::Instant;

use crate::command::{Body, HttpMethod};
use crate::config::secret::SensitiveString;
use crate::response_template::field::TrackedField;

/// Maximum response body size read into memory for capture extraction or
/// response template processing. Prevents OOM when a target server returns
/// unexpectedly large responses (e.g. 100 VUs × 100 MB = 10 GB).
const MAX_RESPONSE_BODY_SIZE: usize = 10 * 1024 * 1024; // 10 MiB

// ── Body format ───────────────────────────────────────────────────────────────

pub enum BodyFormat {
    Json,
}

// ── Shared per-run config ─────────────────────────────────────────────────────

pub struct RequestConfig {
    pub client: reqwest::Client,
    pub host: Arc<String>,
    pub method: HttpMethod,
    pub body: Arc<Option<Body>>,
    pub tracked_fields: Option<Arc<Vec<TrackedField>>>,
    /// Static headers applied to every request in the run.
    /// Stored as `Arc` so the list is shared cheaply across concurrent tasks.
    /// Values are `SensitiveString` so secrets are redacted in debug output.
    pub headers: Arc<Vec<(String, SensitiveString)>>,
}

impl RequestConfig {
    /// Resolves the body for a single request.
    /// Returns `(content, content_type)`, or `None` if no body is configured.
    /// `template_body` takes priority when provided (pre-generated template output).
    pub fn resolve_body(&self, template_body: Option<String>) -> Option<(String, &'static str)> {
        if let Some(content) = template_body {
            return Some((content, "application/json"));
        }
        self.body.as_ref().as_ref().map(|b| match b {
            Body::Formatted { content, format } => (
                content.clone(),
                match format {
                    BodyFormat::Json => "application/json",
                },
            ),
        })
    }
}

// ── Result ────────────────────────────────────────────────────────────────────

pub struct RequestResult {
    pub duration: Duration,
    /// Wall-clock instant at which the response was received (or the error occurred).
    /// Used by the output module to bucket results into per-stage windows when
    /// `mode == Curve`. Zero-cost in fixed mode where `curve_stages` is `None`.
    pub completed_at: Instant,
    pub success: bool,
    pub status_code: Option<u16>,
    pub response_body: Option<String>,
}

// ── RequestRecord ─────────────────────────────────────────────────────────────

/// Lightweight per-request record sent from VU to coordinator over the channel.
///
/// Unlike `RequestResult`, carries no raw response body — any extraction is done
/// inside the VU before sending, keeping KB-sized bodies off the channel.
pub struct RequestRecord {
    pub duration: std::time::Duration,
    /// Wall-clock instant at which the response was received (or the error occurred).
    /// Used by the drain task to bucket results into per-stage windows in curve mode.
    pub completed_at: Instant,
    pub success: bool,
    pub status_code: Option<u16>,
    /// Present only when a response template is active and extraction succeeded.
    pub extraction: Option<crate::response_template::extractor::ExtractionResult>,
    /// Optional scenario name associated with this request.
    pub scenario: Option<Arc<str>>,
    /// Optional step name inside a scenario.
    pub step: Option<Arc<str>>,
    /// True when this record represents a step that was skipped (not executed).
    /// Skipped records count toward `total_requests` but do not contribute to
    /// latency histograms or status code distributions.
    pub skipped: bool,
}

impl RequestResult {
    /// Constructs a `RequestResult` with all fields explicit.
    ///
    /// Use this constructor rather than struct literals so that adding fields in the
    /// future causes a compile error at every call site, preventing silent omissions.
    pub fn new(
        duration: Duration,
        success: bool,
        status_code: Option<u16>,
        response_body: Option<String>,
    ) -> Self {
        Self {
            duration,
            completed_at: Instant::now(),
            success,
            status_code,
            response_body,
        }
    }
}

// ── Request builder ───────────────────────────────────────────────────────────

pub struct Request {
    client: reqwest::Client,
    url: Arc<String>,
    method: HttpMethod,
    body: Option<(String, &'static str)>,
    headers: Option<Arc<Vec<(String, String)>>>,
    capture_response: bool,
}

impl Request {
    pub fn new(client: reqwest::Client, url: Arc<String>, method: HttpMethod) -> Self {
        Self {
            client,
            url,
            method,
            body: None,
            headers: None,
            capture_response: false,
        }
    }

    pub fn body(mut self, content: String, content_type: &'static str) -> Self {
        self.body = Some((content, content_type));
        self
    }

    /// Attach a list of custom HTTP headers.
    /// These are applied after the auto-set `Content-Type`, so a user-supplied
    /// `Content-Type` header will override the auto-set one.
    pub fn headers(mut self, headers: Arc<Vec<(String, String)>>) -> Self {
        self.headers = Some(headers);
        self
    }

    pub fn read_response(mut self) -> Self {
        self.capture_response = true;
        self
    }

    pub async fn execute(self) -> RequestResult {
        let start = Instant::now();
        let mut req = match self.method {
            HttpMethod::Get => self.client.get(self.url.as_str()),
            HttpMethod::Post => self.client.post(self.url.as_str()),
            HttpMethod::Put => self.client.put(self.url.as_str()),
            HttpMethod::Patch => self.client.patch(self.url.as_str()),
            HttpMethod::Delete => self.client.delete(self.url.as_str()),
        };
        if let Some((content, content_type)) = self.body {
            req = req.header("Content-Type", content_type).body(content);
        }
        // Apply user-supplied headers AFTER body/Content-Type so they take precedence.
        if let Some(headers) = self.headers {
            for (name, value) in headers.iter() {
                req = req.header(name, value);
            }
        }

        match req.send().await {
            Ok(resp) => {
                let status = resp.status();
                let response_body = if self.capture_response {
                    // Pre-check content-length when available to reject oversized
                    // responses before buffering. Chunked responses without
                    // content-length fall through to the post-read check.
                    let too_large = resp
                        .content_length()
                        .is_some_and(|len| len > MAX_RESPONSE_BODY_SIZE as u64);
                    if too_large {
                        None
                    } else {
                        match resp.bytes().await {
                            Ok(bytes) if bytes.len() <= MAX_RESPONSE_BODY_SIZE => {
                                String::from_utf8(bytes.to_vec()).ok()
                            }
                            _ => None,
                        }
                    }
                } else {
                    None
                };
                let duration = start.elapsed();
                let completed_at = Instant::now();
                RequestResult {
                    duration,
                    completed_at,
                    success: status.is_success(),
                    status_code: Some(status.as_u16()),
                    response_body,
                }
            }
            Err(_) => {
                let duration = start.elapsed();
                let completed_at = Instant::now();
                RequestResult {
                    duration,
                    completed_at,
                    success: false,
                    status_code: None,
                    response_body: None,
                }
            }
        }
    }
}