From e121fe28bb82a155e51918c07cf7af8f84461b6a Mon Sep 17 00:00:00 2001
From: Anders Olsson <anders.e.olsson@gmail.com>
Date: Mon, 25 May 2026 11:37:19 +0200
Subject: [PATCH] feat(supervisor): LogSink fans out to file, ring buffer,
 broadcast

---
 crates/xy-supervisor/src/lib.rs  |  2 +-
 crates/xy-supervisor/src/logs.rs | 75 ++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/crates/xy-supervisor/src/lib.rs b/crates/xy-supervisor/src/lib.rs
index e8f7fb1..9a6df14 100644
--- a/crates/xy-supervisor/src/lib.rs
+++ b/crates/xy-supervisor/src/lib.rs
@@ -8,6 +8,6 @@ pub mod retry_window;
 
 pub use backoff::Backoff;
 pub use child::{ChildHandle, MockChild, MockChildController};
-pub use logs::{RecordedLine, RingBuffer, RotatingLogWriter};
+pub use logs::{LogSink, RecordedLine, RingBuffer, RotatingLogWriter};
 pub use policy::{RestartDecision, decide};
 pub use retry_window::RetryWindow;
diff --git a/crates/xy-supervisor/src/logs.rs b/crates/xy-supervisor/src/logs.rs
index a2c80f7..a343585 100644
--- a/crates/xy-supervisor/src/logs.rs
+++ b/crates/xy-supervisor/src/logs.rs
@@ -4,6 +4,9 @@ use std::io::Write;
 use std::path::{Path, PathBuf};
 use std::sync::{Arc, Mutex};
 
+use tokio::sync::broadcast;
+use xy_protocol::rpc::{LogLine, LogStream};
+
 pub struct RotatingLogWriter {
     base: PathBuf,
     max_bytes: u64,
@@ -121,6 +124,62 @@ impl RingBuffer {
     }
 }
 
+const LOG_BROADCAST_CAP: usize = 256;
+
+#[derive(Clone)]
+pub struct LogSink {
+    pub server_name: String,
+    writer: Arc<Mutex<RotatingLogWriter>>,
+    pub ring: RingBuffer,
+    pub broadcast: broadcast::Sender<LogLine>,
+}
+
+impl LogSink {
+    pub fn new(
+        server_name: String,
+        writer: RotatingLogWriter,
+        ring_capacity_bytes: usize,
+    ) -> Self {
+        let (tx, _) = broadcast::channel(LOG_BROADCAST_CAP);
+        Self {
+            server_name,
+            writer: Arc::new(Mutex::new(writer)),
+            ring: RingBuffer::new(ring_capacity_bytes),
+            broadcast: tx,
+        }
+    }
+
+    pub fn record(&self, stream: LogStream, line: String) {
+        let ts = now_unix_ms();
+        let tag = match stream {
+            LogStream::Stdout => "[out]",
+            LogStream::Stderr => "[err]",
+        };
+        if let Err(e) = self.writer.lock().unwrap().write_line(tag, &line) {
+            tracing::warn!(server = %self.server_name, error = %e, "log file write failed");
+        }
+        self.ring.push(RecordedLine {
+            stream,
+            line: line.clone(),
+            ts_unix_ms: ts,
+        });
+        let _ = self.broadcast.send(LogLine {
+            subscription_id: 0,
+            name: self.server_name.clone(),
+            stream,
+            line,
+            ts_unix_ms: ts,
+        });
+    }
+}
+
+fn now_unix_ms() -> u64 {
+    std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .map(|d| d.as_millis() as u64)
+        .unwrap_or(0)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -192,4 +251,20 @@ mod tests {
         assert_eq!(snap[0].line, "line3");
         assert_eq!(snap[1].line, "line4");
     }
+
+    #[tokio::test]
+    async fn log_sink_records_and_broadcasts() {
+        let dir = tempdir().unwrap();
+        let writer = RotatingLogWriter::open(&dir.path().join("s.log"), 1024, 3).unwrap();
+        let sink = LogSink::new("s".to_string(), writer, 1024);
+        let mut rx = sink.broadcast.subscribe();
+        sink.record(LogStream::Stdout, "hello".to_string());
+        let got = tokio::time::timeout(std::time::Duration::from_millis(100), rx.recv())
+            .await
+            .unwrap()
+            .unwrap();
+        assert_eq!(got.line, "hello");
+        assert_eq!(got.stream, LogStream::Stdout);
+        assert_eq!(sink.ring.snapshot_tail(None).len(), 1);
+    }
 }