feat: add background database auto-updater with hot-reload

src/main.rs

@@ -1,6 +1,7 @@
 mod config;
 mod db;
 mod models;
+mod updater;
 
 fn main() {
     let _config = config::Config::from_env();

src/updater.rs

@@ -0,0 +1,73 @@
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use std::time::Duration;
+
+use tokio::fs;
+use tokio::io::AsyncWriteExt;
+use tracing::error;
+
+use crate::db::{DbReader, SharedDb, load_db};
+
+pub async fn ensure_db_exists(db_path: &Path, update_url: &str) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    if db_path.exists() {
+        return Ok(());
+    }
+
+    if let Some(parent) = db_path.parent() {
+        fs::create_dir_all(parent).await?;
+    }
+
+    download_db(update_url, db_path).await
+}
+
+async fn download_db(url: &str, dest: &Path) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    let tmp_path = dest.with_extension("mmdb.tmp");
+    let client = reqwest::Client::builder()
+        .timeout(Duration::from_secs(300))
+        .build()?;
+
+    let response = client.get(url).send().await?.error_for_status()?;
+    let bytes = response.bytes().await?;
+
+    let mut file = fs::File::create(&tmp_path).await?;
+    file.write_all(&bytes).await?;
+    file.flush().await?;
+    drop(file);
+
+    validate_db(&tmp_path)?;
+    fs::rename(&tmp_path, dest).await?;
+
+    Ok(())
+}
+
+fn validate_db(path: &Path) -> Result<DbReader, Box<dyn std::error::Error + Send + Sync>> {
+    load_db(path).map_err(|e| e.into())
+}
+
+pub fn spawn_updater(
+    shared_db: SharedDb,
+    db_path: PathBuf,
+    update_url: String,
+    interval_hours: u64,
+) {
+    tokio::spawn(async move {
+        let interval = Duration::from_secs(interval_hours * 3600);
+        loop {
+            tokio::time::sleep(interval).await;
+            if let Err(e) = update_db(&shared_db, &db_path, &update_url).await {
+                error!("database update failed: {e}");
+            }
+        }
+    });
+}
+
+async fn update_db(
+    shared_db: &SharedDb,
+    db_path: &Path,
+    update_url: &str,
+) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    download_db(update_url, db_path).await?;
+    let reader = load_db(db_path)?;
+    shared_db.store(Arc::new(reader));
+    Ok(())
+}