feat: add Rust reverse proxy with JSON logging

- Axum-based API server with Unix socket and TCP support
- Custom tracing formatters for Railway-compatible JSON logs
- SvelteKit hooks and Vite plugin for unified logging
- Justfile updated for concurrent dev workflow with hl log viewer
This commit is contained in:
2026-01-04 18:21:00 -06:00
parent 07ea1c093e
commit d86027d27a
19 changed files with 3069 additions and 11 deletions
+418
View File
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use axum::{
Json, Router,
extract::{Request, State},
http::{HeaderMap, StatusCode},
response::{IntoResponse, Response},
routing::get,
};
use clap::Parser;
use serde::{Deserialize, Serialize};
use std::path::PathBuf;
use std::sync::Arc;
use tower_http::{cors::CorsLayer, trace::TraceLayer};
use tracing_subscriber::{EnvFilter, layer::SubscriberExt, util::SubscriberInitExt};
mod config;
mod formatter;
mod middleware;
use config::{Args, ListenAddr};
use formatter::{CustomJsonFormatter, CustomPrettyFormatter};
use middleware::RequestIdLayer;
fn init_tracing() {
let use_json = std::env::var("LOG_JSON")
.map(|v| v == "true" || v == "1")
.unwrap_or(false);
// Build the EnvFilter
// Priority: RUST_LOG > LOG_LEVEL > default
let filter = if let Ok(rust_log) = std::env::var("RUST_LOG") {
// RUST_LOG overwrites everything
EnvFilter::new(rust_log)
} else {
// Get LOG_LEVEL for our crate, default based on build profile
let our_level = std::env::var("LOG_LEVEL").unwrap_or_else(|_| {
if cfg!(debug_assertions) {
"debug".to_string()
} else {
"info".to_string()
}
});
// Default other crates to WARN, our crate to LOG_LEVEL
EnvFilter::new(format!("warn,api={}", our_level))
};
if use_json {
tracing_subscriber::registry()
.with(filter)
.with(
tracing_subscriber::fmt::layer()
.event_format(CustomJsonFormatter)
.fmt_fields(tracing_subscriber::fmt::format::DefaultFields::new())
.with_ansi(false), // Disable ANSI codes in JSON mode
)
.init();
} else {
tracing_subscriber::registry()
.with(filter)
.with(tracing_subscriber::fmt::layer().event_format(CustomPrettyFormatter))
.init();
}
}
#[tokio::main]
async fn main() {
// Initialize tracing with configurable format and levels
init_tracing();
// Parse CLI arguments and environment variables
let args = Args::parse();
// Validate we have at least one listen address
if args.listen.is_empty() {
eprintln!("Error: At least one --listen address is required");
std::process::exit(1);
}
// Create shared application state
let state = Arc::new(AppState {
downstream_url: args.downstream.clone(),
});
// Build router with shared state
let app = Router::new()
.nest("/api", api_routes().fallback(api_404_handler))
.fallback(isr_handler)
.layer(TraceLayer::new_for_http())
.layer(RequestIdLayer::new(args.trust_request_id.clone()))
.layer(CorsLayer::permissive())
.with_state(state);
// Spawn a listener for each address
let mut tasks = Vec::new();
for listen_addr in &args.listen {
let app = app.clone();
let listen_addr = listen_addr.clone();
let task = tokio::spawn(async move {
match listen_addr {
ListenAddr::Tcp(addr) => {
let listener = tokio::net::TcpListener::bind(addr)
.await
.expect("Failed to bind TCP listener");
// Format as clickable URL
let url = if addr.is_ipv6() {
format!("http://[{}]:{}", addr.ip(), addr.port())
} else {
format!("http://{}:{}", addr.ip(), addr.port())
};
tracing::info!(url, "Listening on TCP");
axum::serve(listener, app)
.await
.expect("Server error on TCP listener");
}
ListenAddr::Unix(path) => {
// Remove existing socket file if it exists
let _ = std::fs::remove_file(&path);
let listener = tokio::net::UnixListener::bind(&path)
.expect("Failed to bind Unix socket listener");
tracing::info!(socket = %path.display(), "Listening on Unix socket");
axum::serve(listener, app)
.await
.expect("Server error on Unix socket listener");
}
}
});
tasks.push(task);
}
// Wait for all listeners (this will run forever unless interrupted)
for task in tasks {
task.await.expect("Listener task panicked");
}
}
/// Shared application state
#[derive(Clone)]
struct AppState {
downstream_url: String,
}
/// Custom error type for proxy operations
#[derive(Debug)]
enum ProxyError {
/// Network error (connection failed, timeout, etc.)
Network(reqwest::Error),
}
impl std::fmt::Display for ProxyError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
ProxyError::Network(e) => write!(f, "Network error: {}", e),
}
}
}
impl std::error::Error for ProxyError {}
/// Check if a path represents a static asset that should be logged at TRACE level
fn is_static_asset(path: &str) -> bool {
path.starts_with("/node_modules/")
|| path.starts_with("/@") // Vite internals like /@vite/client, /@fs/, /@id/
|| path.starts_with("/.svelte-kit/")
|| path.starts_with("/.well-known/")
|| path.ends_with(".woff2")
|| path.ends_with(".woff")
|| path.ends_with(".ttf")
|| path.ends_with(".ico")
|| path.ends_with(".png")
|| path.ends_with(".jpg")
|| path.ends_with(".svg")
|| path.ends_with(".webp")
|| path.ends_with(".css")
|| path.ends_with(".js")
|| path.ends_with(".map")
}
/// Check if a path represents a page route (heuristic: no file extension)
fn is_page_route(path: &str) -> bool {
!path.starts_with("/node_modules/")
&& !path.starts_with("/@")
&& !path.starts_with("/.svelte-kit/")
&& !path.contains('.') // Simple heuristic: no extension = likely a page
}
// API routes for data endpoints
fn api_routes() -> Router<Arc<AppState>> {
Router::new()
.route("/health", get(health_handler))
.route("/projects", get(projects_handler))
}
// Health check endpoint
async fn health_handler() -> impl IntoResponse {
(StatusCode::OK, "OK")
}
// API 404 fallback handler - catches unmatched /api/* routes
async fn api_404_handler(uri: axum::http::Uri) -> impl IntoResponse {
tracing::warn!(path = %uri.path(), "API route not found");
(
StatusCode::NOT_FOUND,
Json(serde_json::json!({
"error": "Not found",
"path": uri.path()
})),
)
}
// Project data structure
#[derive(Debug, Clone, Serialize, Deserialize)]
struct ProjectLink {
url: String,
#[serde(skip_serializing_if = "Option::is_none")]
title: Option<String>,
}
#[derive(Debug, Clone, Serialize, Deserialize)]
struct Project {
id: String,
name: String,
#[serde(rename = "shortDescription")]
short_description: String,
#[serde(skip_serializing_if = "Option::is_none")]
icon: Option<String>,
links: Vec<ProjectLink>,
}
// Projects endpoint - returns hardcoded project data for now
async fn projects_handler() -> impl IntoResponse {
let projects = vec![
Project {
id: "1".to_string(),
name: "xevion.dev".to_string(),
short_description: "Personal portfolio with fuzzy tag discovery".to_string(),
icon: None,
links: vec![ProjectLink {
url: "https://github.com/Xevion/xevion.dev".to_string(),
title: Some("GitHub".to_string()),
}],
},
Project {
id: "2".to_string(),
name: "Contest".to_string(),
short_description: "Competitive programming problem archive".to_string(),
icon: None,
links: vec![
ProjectLink {
url: "https://github.com/Xevion/contest".to_string(),
title: Some("GitHub".to_string()),
},
ProjectLink {
url: "https://contest.xevion.dev".to_string(),
title: Some("Demo".to_string()),
},
],
},
];
Json(projects)
}
// ISR handler - proxies to Bun SSR server
// This is the fallback for all routes not matched by /api/*
#[tracing::instrument(skip(state, req), fields(path = %req.uri().path()))]
async fn isr_handler(State(state): State<Arc<AppState>>, req: Request) -> Response {
let uri = req.uri();
let path = uri.path();
let query = uri.query().unwrap_or("");
// Check if API route somehow reached ISR handler (shouldn't happen)
if path.starts_with("/api/") {
tracing::error!("API request reached ISR handler - routing bug!");
return (
StatusCode::INTERNAL_SERVER_ERROR,
"Internal routing error",
)
.into_response();
}
// Build URL for Bun server
let bun_url = if query.is_empty() {
format!("{}{}", state.downstream_url, path)
} else {
format!("{}{}?{}", state.downstream_url, path, query)
};
// Track request timing
let start = std::time::Instant::now();
// TODO: Add ISR caching layer here (moka, singleflight, stale-while-revalidate)
// For now, just proxy directly to Bun
match proxy_to_bun(&bun_url, &state.downstream_url).await {
Ok((status, headers, body)) => {
let duration_ms = start.elapsed().as_millis() as u64;
let cache = "miss"; // Hardcoded for now, will change when caching is implemented
// Intelligent logging based on path type and status
let is_static = is_static_asset(path);
let is_page = is_page_route(path);
match (status.as_u16(), is_static, is_page) {
// Static assets - success at TRACE
(200..=299, true, _) => {
tracing::trace!(status = status.as_u16(), duration_ms, cache, "ISR request");
}
// Static assets - 404 at WARN
(404, true, _) => {
tracing::warn!(
status = status.as_u16(),
duration_ms,
cache,
"ISR request - missing asset"
);
}
// Static assets - server error at ERROR
(500..=599, true, _) => {
tracing::error!(
status = status.as_u16(),
duration_ms,
cache,
"ISR request - server error"
);
}
// Page routes - success at DEBUG
(200..=299, _, true) => {
tracing::debug!(status = status.as_u16(), duration_ms, cache, "ISR request");
}
// Page routes - 404 silent (normal case for non-existent pages)
(404, _, true) => {}
// Page routes - server error at ERROR
(500..=599, _, _) => {
tracing::error!(
status = status.as_u16(),
duration_ms,
cache,
"ISR request - server error"
);
}
// Default fallback - DEBUG
_ => {
tracing::debug!(status = status.as_u16(), duration_ms, cache, "ISR request");
}
}
// Forward response
(status, headers, body).into_response()
}
Err(err) => {
let duration_ms = start.elapsed().as_millis() as u64;
tracing::error!(
error = %err,
url = %bun_url,
duration_ms,
"Failed to proxy to Bun"
);
(
StatusCode::BAD_GATEWAY,
format!("Failed to render page: {}", err),
)
.into_response()
}
}
}
// Proxy a request to the Bun SSR server, returning status, headers and body
async fn proxy_to_bun(
url: &str,
downstream_url: &str,
) -> Result<(StatusCode, HeaderMap, String), ProxyError> {
// Check if downstream is a Unix socket path
let client = if downstream_url.starts_with('/') || downstream_url.starts_with("./") {
// Unix socket
let path = PathBuf::from(downstream_url);
reqwest::Client::builder()
.unix_socket(path)
.build()
.map_err(ProxyError::Network)?
} else {
// Regular HTTP
reqwest::Client::new()
};
let response = client.get(url).send().await.map_err(ProxyError::Network)?;
// Extract status code
let status = StatusCode::from_u16(response.status().as_u16())
.unwrap_or(StatusCode::INTERNAL_SERVER_ERROR);
// Convert reqwest headers to axum HeaderMap
let mut headers = HeaderMap::new();
for (name, value) in response.headers() {
// Skip hop-by-hop headers and content-length (axum will recalculate it)
let name_str = name.as_str();
if name_str == "transfer-encoding"
|| name_str == "connection"
|| name_str == "content-length"
{
continue;
}
if let Ok(header_name) = axum::http::HeaderName::try_from(name.as_str()) {
if let Ok(header_value) = axum::http::HeaderValue::try_from(value.as_bytes()) {
headers.insert(header_name, header_value);
}
}
}
let body = response.text().await.map_err(ProxyError::Network)?;
Ok((status, headers, body))
}