max / makenotwork

3.1 KB · 77 lines History Blame Raw

1	//! Whether the platform changelog is published, for the footer link.
2	//!
3	//! `base.html` renders the site footer on every page and cannot await a query,
4	//! so the answer lives in a process-global flag that a background task
5	//! refreshes. `/changelog` resolves through
6	//! `db::projects::get_public_project_by_slug(CHANGELOG_PROJECT_SLUG)`; when no
7	//! such published project exists the route 404s, which turned the footer link
8	//! into a sitewide dead end.
9	//!
10	//! The flag starts `false`, so until the first refresh lands the footer omits a
11	//! link we cannot yet prove resolves. The route is unchanged: this only decides
12	//! whether visitors are pointed at it. Publish a changelog project and the link
13	//! comes back on its own within `REFRESH_INTERVAL_SECS`.
14	//!
15	//! Per-process, not per-instance-cluster: the refresher runs in every instance
16	//! rather than under the scheduler's advisory lock, so a second instance in a
17	//! rolling deploy does not serve a stale footer.
18
19	use std::sync::atomic::{AtomicBool, Ordering};
20
21	use sqlx::PgPool;
22	use tokio::sync::watch;
23	use tokio::task::JoinHandle;
24
25	use crate::constants;
26	use crate::db::{self, Slug};
27
28	static PUBLISHED: AtomicBool = AtomicBool::new(false);
29
30	/// How often each instance re-checks whether the changelog project is public.
31	/// One indexed lookup per minute per instance, cheap enough that the link's
32	/// reappearance is prompt without a write-path hook in every publish route.
33	const REFRESH_INTERVAL_SECS: u64 = 60;
34
35	/// Whether the footer should link to `/changelog`. Called from `base.html`.
36	pub fn is_published() -> bool {
37	PUBLISHED.load(Ordering::Relaxed)
38	}
39
40	/// Re-read the changelog project's visibility into the flag.
41	///
42	/// A failed query keeps the previous value rather than hiding the link: a
43	/// transient DB error is not evidence that the changelog went away.
44	#[tracing::instrument(skip_all)]
45	pub async fn refresh(pool: &PgPool) {
46	let slug = Slug::from_trusted(constants::CHANGELOG_PROJECT_SLUG.to_owned());
47	match db::projects::get_public_project_by_slug(pool, &slug).await {
48	Ok(project) => PUBLISHED.store(project.is_some(), Ordering::Relaxed),
49	Err(e) => {
50	tracing::warn!(error = ?e, "changelog visibility refresh failed, keeping last value");
51	}
52	}
53	}
54
55	/// Spawn the per-instance refresh loop. Drop the shutdown sender to stop it.
56	/// Refreshes once immediately so the first rendered page is already accurate.
57	pub fn spawn_refresher(pool: PgPool, mut shutdown_rx: watch::Receiver<()>) -> JoinHandle<()> {
58	tokio::spawn(async move {
59	let mut interval =
60	tokio::time::interval(std::time::Duration::from_secs(REFRESH_INTERVAL_SECS));
61	interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);
62
63	loop {
64	tokio::select! {
65	_ = interval.tick() => refresh(&pool).await,
66	_ = shutdown_rx.changed() => break,
67	}
68	}
69	})
70	}
71
72	/// Force the flag for tests that render the footer without a database.
73	#[doc(hidden)]
74	pub fn set_published_for_test(published: bool) {
75	PUBLISHED.store(published, Ordering::Relaxed);
76	}
77