memoryd: a reported turn decided after loopd has its answer, from brokerd and the log

Co-Authored-By: ornith-1.5-35b-a3b <agent@wntrmute.dev>

crates/memoryd/tests/support/brokerd.rs

@@ -0,0 +1,127 @@
+//! A fake `brokerd` state socket for tests: it records each question and answers with a fixed
+//! state, an error frame, or nothing at all (it holds the connection open without a byte). It
+//! stops, and releases every held connection, when dropped; every wait has a deadline. Do not
+//! edit.
+
+#![allow(dead_code)] // each test file uses a different part of this module
+
+use std::os::unix::net::{UnixListener, UnixStream};
+use std::path::{Path, PathBuf};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, Mutex};
+use std::thread::JoinHandle;
+use std::time::{Duration, Instant};
+
+use bxcore::{
+    Envelope, ErrorCode, Message, PROTOCOL_VERSION, SessionStateReply, WireError, read_frame,
+    write_frame,
+};
+
+/// How the fake answers.
+#[derive(Debug, Clone)]
+pub enum Answer {
+    State(SessionStateReply),
+    Error(String),
+    /// Read the question, then send nothing until the fake is dropped (at most 30 s).
+    Hang,
+}
+
+pub struct FakeBrokerd {
+    path: PathBuf,
+    stop: Arc<AtomicBool>,
+    seen: Arc<Mutex<Vec<Envelope>>>,
+    accept: Option<JoinHandle<()>>,
+}
+
+impl FakeBrokerd {
+    /// Listen on `path` (its directory is made) and answer every connection with `answer`.
+    pub fn start(path: &Path, answer: Answer) -> FakeBrokerd {
+        if let Some(dir) = path.parent() {
+            std::fs::create_dir_all(dir).unwrap();
+        }
+        let _ = std::fs::remove_file(path);
+        let listener = UnixListener::bind(path).unwrap();
+        let stop = Arc::new(AtomicBool::new(false));
+        let seen = Arc::new(Mutex::new(Vec::new()));
+        let (stop_accept, seen_accept) = (Arc::clone(&stop), Arc::clone(&seen));
+        let accept = std::thread::spawn(move || {
+            for stream in listener.incoming() {
+                if stop_accept.load(Ordering::SeqCst) {
+                    return;
+                }
+                let Ok(stream) = stream else { return };
+                let (stop, seen, answer) = (
+                    Arc::clone(&stop_accept),
+                    Arc::clone(&seen_accept),
+                    answer.clone(),
+                );
+                std::thread::spawn(move || serve(stream, &answer, &seen, &stop));
+            }
+        });
+        FakeBrokerd {
+            path: path.to_path_buf(),
+            stop,
+            seen,
+            accept: Some(accept),
+        }
+    }
+
+    /// Every question read so far, in order.
+    pub fn seen(&self) -> Vec<Envelope> {
+        self.seen.lock().unwrap().clone()
+    }
+
+    /// Waits up to 10 s until at least `n` questions were read; true if they were.
+    pub fn wait_for(&self, n: usize) -> bool {
+        let deadline = Instant::now() + Duration::from_secs(10);
+        while Instant::now() < deadline {
+            if self.seen().len() >= n {
+                return true;
+            }
+            std::thread::sleep(Duration::from_millis(10));
+        }
+        false
+    }
+}
+
+fn serve(mut stream: UnixStream, answer: &Answer, seen: &Mutex<Vec<Envelope>>, stop: &AtomicBool) {
+    let _ = stream.set_read_timeout(Some(Duration::from_secs(10)));
+    let Ok(question) = read_frame(&mut stream) else {
+        return;
+    };
+    let id = question.id;
+    seen.lock().unwrap().push(question);
+    let msg = match answer {
+        Answer::State(state) => Message::SessionStateReply(state.clone()),
+        Answer::Error(detail) => Message::Error(WireError {
+            code: ErrorCode::Internal,
+            detail: detail.clone(),
+        }),
+        Answer::Hang => {
+            let deadline = Instant::now() + Duration::from_secs(30);
+            while !stop.load(Ordering::SeqCst) && Instant::now() < deadline {
+                std::thread::sleep(Duration::from_millis(10));
+            }
+            return;
+        }
+    };
+    let env = Envelope {
+        v: PROTOCOL_VERSION,
+        id,
+        r#final: true,
+        msg,
+    };
+    let _ = write_frame(&mut stream, &env);
+}
+
+impl Drop for FakeBrokerd {
+    fn drop(&mut self) {
+        self.stop.store(true, Ordering::SeqCst);
+        // Wakes the accept loop, which then sees `stop`.
+        let _ = UnixStream::connect(&self.path);
+        if let Some(accept) = self.accept.take() {
+            let _ = accept.join();
+        }
+        let _ = std::fs::remove_file(&self.path);
+    }
+}