max / makenotwork

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1	//! A stand-in Multithreaded, so the forum-membership screens can be put under
2	//! load without a real instance.
3	//!
4	//! The two described forum screens (`src/quasi/forum_memberships.rs`) are the
5	//! only ones whose work is an outbound HTTP call rather than a database round
6	//! trip, and quasi's router is sync: the described version holds a
7	//! BLOCKING-POOL thread for that whole call, where the Askama version pays the
8	//! same latency on a runtime worker. Every runtime number about the description
9	//! layer so far came from sub-millisecond sqlx queries, so nothing has measured
10	//! that regime.
11	//!
12	//! What makes it measurable is that the upstream latency becomes the variable.
13	//! This stub sleeps `LOAD_MT_LATENCY_MS` before answering, so a run can be
14	//! repeated at 0ms, 50ms, 500ms and 5s and the question becomes the threshold at
15	//! which occupancy starts to cost something, rather than a pass/fail against
16	//! whatever a real instance happened to be doing that afternoon.
17	//!
18	//! It sleeps on the runtime rather than blocking, which is the point: the stub
19	//! must not itself consume the pool being measured.
20
21	use axum::Router;
22	use axum::extract::Path;
23	use axum::routing::get;
24	use std::time::Duration;
25
26	/// A running stub, alive until it is dropped.
27	pub(super) struct MtStub {
28	/// What to hand `IntegrationsConfig::mt_base_url`.
29	base_url: String,
30	server: tokio::task::JoinHandle<()>,
31	}
32
33	impl MtStub {
34	/// Bind on an ephemeral port and start answering.
35	///
36	/// `latency` is slept before every answer. `memberships` is how many rows
37	/// come back, which decides how much describing the screen has to do once
38	/// the call lands.
39	pub(super) async fn start(latency: Duration, memberships: usize) -> Self {
40	let app = Router::new().route(
41	"/api/user/{user_id}/summary",
42	get(move \|Path(_user_id): Path<String>\| async move {
43	if !latency.is_zero() {
44	tokio::time::sleep(latency).await;
45	}
46	axum::Json(summary(memberships))
47	}),
48	);
49
50	let listener = tokio::net::TcpListener::bind("127.0.0.1:0")
51	.await
52	.expect("MT stub could not bind");
53	let addr = listener.local_addr().expect("MT stub has no address");
54
55	let server = tokio::spawn(async move {
56	// Ignore the result: the runner drops the stub at the end of the
57	// run and a shutdown error there is not a finding.
58	let _ = axum::serve(listener, app).await;
59	});
60
61	MtStub {
62	base_url: format!("http://{addr}"),
63	server,
64	}
65	}
66
67	pub(super) fn base_url(&self) -> String {
68	self.base_url.clone()
69	}
70	}
71
72	impl Drop for MtStub {
73	fn drop(&mut self) {
74	self.server.abort();
75	}
76	}
77
78	/// The shape `fetch` in `src/quasi/forum_memberships.rs` reads, and the same
79	/// shape the Askama handler in `routes::pages::public::landing` reads. Both
80	/// sides of the comparison parse this, so a change to it moves both together.
81	fn summary(memberships: usize) -> serde_json::Value {
82	let rows: Vec<serde_json::Value> = (0..memberships)
83	.map(\|i\| {
84	serde_json::json!({
85	"community_slug": format!("community-{i}"),
86	"community_name": format!("Community {i}"),
87	"role": if i == 0 { "Moderator" } else { "Member" },
88	"post_count": 40 + i as i64,
89	"joined_at": "2026-03-14T09:00:00Z",
90	})
91	})
92	.collect();
93	serde_json::json!({ "memberships": rows })
94	}
95