warn if a streamer op takes too long

My odroid setup has been occasionally (about once a week) losing about 15
seconds of recordings on all cameras. I'm not sure why. So I'm labelling all
the likely suspect spots and logging if any of them takes longer than a
second. I think this will give me more information; hopefully narrow it down
to network or local disk I/O.

src/clock.rs

@@ -76,6 +76,34 @@ impl Clocks for RealClocks {
     }
 }
 
+/// Logs a warning if the TimerGuard lives "too long", using the label created by a supplied
+/// function.
+pub struct TimerGuard<'a, C: Clocks + 'a, S: AsRef<str>, F: FnOnce() -> S + 'a> {
+    clocks: &'a C,
+    label_f: Option<F>,
+    start: Timespec,
+}
+
+impl<'a, C: Clocks + 'a, S: AsRef<str>, F: FnOnce() -> S + 'a> TimerGuard<'a, C, S, F> {
+    pub fn new(clocks: &'a C, label_f: F) -> Self {
+        TimerGuard {
+            clocks,
+            label_f: Some(label_f),
+            start: clocks.monotonic(),
+        }
+    }
+}
+
+impl<'a, C: Clocks + 'a, S: AsRef<str>, F: FnOnce() -> S + 'a> Drop for TimerGuard<'a, C, S, F> {
+    fn drop(&mut self) {
+        let elapsed = self.clocks.monotonic() - self.start;
+        if elapsed.num_seconds() >= 1 {
+            let label_f = self.label_f.take().unwrap();
+            warn!("{} took {}!", label_f().as_ref(), elapsed);
+        }
+    }
+}
+
 /// Simulated clock for testing.
 #[cfg(test)]
 pub struct SimulatedClocks {

src/streamer.rs

@@ -28,7 +28,7 @@
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-use clock::Clocks;
+use clock::{Clocks, TimerGuard};
 use db::{Camera, Database};
 use dir;
 use error::Error;
@@ -111,21 +111,29 @@ impl<'a, C, S> Streamer<'a, C, S> where C: 'a + Clocks, S: 'a + stream::Stream {
     fn run_once(&mut self) -> Result<(), Error> {
         info!("{}: Opening input: {}", self.short_name, self.redacted_url);
 
-        let mut stream = self.opener.open(stream::Source::Rtsp(&self.url))?;
+        let mut stream = {
+            let _t = TimerGuard::new(self.clocks, || format!("opening {}", self.redacted_url));
+            self.opener.open(stream::Source::Rtsp(&self.url))?
+        };
         let realtime_offset = self.clocks.realtime() - self.clocks.monotonic();
         // TODO: verify width/height.
         let extra_data = stream.get_extra_data()?;
-        let video_sample_entry_id =
+        let video_sample_entry_id = {
+            let _t = TimerGuard::new(self.clocks, || "inserting video sample entry");
             self.db.lock().insert_video_sample_entry(extra_data.width, extra_data.height,
                                                      extra_data.sample_entry,
-                                                     extra_data.rfc6381_codec)?;
+                                                     extra_data.rfc6381_codec)?
+        };
         debug!("{}: video_sample_entry_id={}", self.short_name, video_sample_entry_id);
         let mut seen_key_frame = false;
         let mut state: Option<WriterState> = None;
         let mut transformed = Vec::new();
         let mut prev = None;
         while !self.shutdown.load(Ordering::SeqCst) {
-            let pkt = stream.get_next()?;
+            let pkt = {
+                let _t = TimerGuard::new(self.clocks, || "getting next packet");
+                stream.get_next()?
+            };
             let pts = pkt.pts().ok_or_else(|| Error::new("packet with no pts".to_owned()))?;
             if !seen_key_frame && !pkt.is_key() {
                 continue;
@@ -138,6 +146,7 @@ impl<'a, C, S> Streamer<'a, C, S> where C: 'a + Clocks, S: 'a + stream::Stream {
             state = if let Some(s) = state {
                 if frame_realtime.sec > s.rotate && pkt.is_key() {
                     trace!("{}: write on normal rotation", self.short_name);
+                    let _t = TimerGuard::new(self.clocks, || "closing writer");
                     prev = Some(s.writer.close(Some(pts))?);
                     None
                 } else {
@@ -157,6 +166,7 @@ impl<'a, C, S> Streamer<'a, C, S> where C: 'a + Clocks, S: 'a + stream::Stream {
                     // the start time.
                     let r = r + if prev.is_none() { self.rotate_interval_sec } else { 0 };
 
+                    let _t = TimerGuard::new(self.clocks, || "creating writer");
                     let w = self.dir.create_writer(&self.syncer_channel, prev, self.camera_id,
                                                    video_sample_entry_id)?;
                     WriterState{
@@ -175,10 +185,13 @@ impl<'a, C, S> Streamer<'a, C, S> where C: 'a + Clocks, S: 'a + stream::Stream {
             } else {
                 orig_data
             };
+            let _t = TimerGuard::new(self.clocks,
+                                      || format!("writing {} bytes", transformed_data.len()));
             s.writer.write(transformed_data, local_time, pts, pkt.is_key())?;
             state = Some(s);
         }
         if let Some(s) = state {
+            let _t = TimerGuard::new(self.clocks, || "closing writer");
             s.writer.close(None)?;
         }
         Ok(())