1 files changed, 47 insertions, 13 deletions

diff --git a/src/modules/blog/module.rs b/src/modules/blog/module.rs
index b1ca8c6..e3a78ef 100644
--- a/src/modules/blog/module.rs
+++ b/src/modules/blog/module.rs
@@ -10,7 +10,10 @@ use {
     url::ROOT_GEMINI_URL,
     xml::{Item as XmlItem, Writer as XmlWriter},
   },
-  std::sync::{LazyLock, Mutex, RwLock},
+  std::sync::{
+    LazyLock, Mutex, RwLock,
+    atomic::{AtomicBool, Ordering},
+  },
 };
 
 pub static POSTS: LazyLock<Mutex<Vec<Post>>> =
@@ -19,12 +22,11 @@ static BLOG_CATEGORIES: LazyLock<RwLock<Vec<BlogCategory>>> =
   LazyLock::new(|| RwLock::new(Vec::new()));
 static BLOG_POSTS: LazyLock<RwLock<Vec<BlogPost>>> =
   LazyLock::new(|| RwLock::new(Vec::new()));
+static REFRESH_IN_PROGRESS: AtomicBool = AtomicBool::new(false);
 
 #[allow(clippy::too_many_lines)]
 pub fn module(router: &mut windmark::router::Router) {
-  std::thread::spawn(fetch_from_notion)
-    .join()
-    .expect("initial Notion fetch failed");
+  trigger_background_refresh("initial");
   track_mount(router, "/blog", "Fuwn's blogs", |context| {
     if should_trigger_manual_refresh(context.url.query()) {
       trigger_manual_refresh();
@@ -126,13 +128,37 @@ fn should_trigger_manual_refresh(query: Option<&str>) -> bool {
   })
 }
 
-fn trigger_manual_refresh() {
+fn begin_refresh() -> bool {
+  REFRESH_IN_PROGRESS
+    .compare_exchange(false, true, Ordering::AcqRel, Ordering::Acquire)
+    .is_ok()
+}
+
+fn finish_refresh() { REFRESH_IN_PROGRESS.store(false, Ordering::Release); }
+
+fn refresh_once(refresh_origin: &str) {
+  if !begin_refresh() {
+    info!(
+      "{refresh_origin} Notion refresh skipped because another refresh is already in progress"
+    );
+
+    return;
+  }
+
   match std::panic::catch_unwind(fetch_from_notion) {
-    Ok(()) => info!("manually refreshed blog data from Notion"),
-    Err(_) => warn!("manual Notion refresh failed"),
+    Ok(()) => info!("{refresh_origin} refreshed blog data from Notion"),
+    Err(_) => warn!("{refresh_origin} Notion refresh failed"),
   }
+
+  finish_refresh();
+}
+
+fn trigger_background_refresh(refresh_origin: &'static str) {
+  std::thread::spawn(move || refresh_once(refresh_origin));
 }
 
+fn trigger_manual_refresh() { trigger_background_refresh("manual"); }
+
 fn construct_header(post: &BlogPost) -> String {
   let title_line = format!("# {}", post.title);
   let has_metadata = post.author.is_some()
@@ -453,18 +479,16 @@ pub fn refresh_loop() {
   loop {
     std::thread::sleep(std::time::Duration::from_secs(refresh_interval_seconds));
 
-    match std::panic::catch_unwind(fetch_from_notion) {
-      Ok(()) => info!("refreshed blog data from Notion"),
-      Err(_) => warn!("failed to refresh blog data from Notion"),
-    }
+    refresh_once("scheduled");
   }
 }
 
 #[cfg(test)]
 mod tests {
   use super::{
-    build_global_posts, build_rss_feed, find_visible_post_by_slug,
-    render_blog_page, should_trigger_manual_refresh, slugify,
+    begin_refresh, build_global_posts, build_rss_feed,
+    find_visible_post_by_slug, finish_refresh, render_blog_page,
+    should_trigger_manual_refresh, slugify,
     visible_posts_for_blog, BLOG_CATEGORIES, BLOG_POSTS,
   };
   use crate::modules::blog::config::{BlogCategory, BlogPost};
@@ -751,4 +775,14 @@ mod tests {
     assert!(!should_trigger_manual_refresh(Some("foo=bar")));
     assert!(!should_trigger_manual_refresh(None));
   }
+
+  #[test]
+  fn manual_refresh_guard_prevents_parallel_refreshes() {
+    finish_refresh();
+    assert!(begin_refresh());
+    assert!(!begin_refresh());
+    finish_refresh();
+    assert!(begin_refresh());
+    finish_refresh();
+  }
 }