Add rate limit to metrics datapoint submission (#4237)

Cleanup

Raise limit on submission threshold

Pick nits and add metrics point

fmt

Fixup compiler warning

Cleanup if-else

Append new point to vec rather than submit

metrics/src/metrics.rs

@@ -133,28 +133,38 @@ impl Default for MetricsAgent {
         Self::new(
             Arc::new(InfluxDbMetricsWriter::new()),
             Duration::from_secs(10),
+            //max per-second datapoint submission limit
+            4000,
         )
     }
 }
 
 impl MetricsAgent {
-    fn new(writer: Arc<MetricsWriter + Send + Sync>, write_frequency: Duration) -> Self {
+    fn new(
+        writer: Arc<MetricsWriter + Send + Sync>,
+        write_frequency_secs: Duration,
+        max_points_per_sec: usize,
+    ) -> Self {
         let (sender, receiver) = channel::<MetricsCommand>();
-        thread::spawn(move || Self::run(&receiver, &writer, write_frequency));
+        thread::spawn(move || {
+            Self::run(&receiver, &writer, write_frequency_secs, max_points_per_sec)
+        });
         Self { sender }
     }
 
     fn run(
         receiver: &Receiver<MetricsCommand>,
         writer: &Arc<MetricsWriter + Send + Sync>,
-        write_frequency: Duration,
+        write_frequency_secs: Duration,
+        max_points_per_sec: usize,
     ) {
         trace!("run: enter");
         let mut last_write_time = Instant::now();
         let mut points = Vec::new();
+        let max_points = write_frequency_secs.as_secs() as usize * max_points_per_sec;
 
         loop {
-            match receiver.recv_timeout(write_frequency / 2) {
+            match receiver.recv_timeout(write_frequency_secs / 2) {
                 Ok(cmd) => match cmd {
                     MetricsCommand::Flush(barrier) => {
                         debug!("metrics_thread: flush");
@@ -180,8 +190,44 @@ impl MetricsAgent {
             }
 
             let now = Instant::now();
-            if now.duration_since(last_write_time) >= write_frequency && !points.is_empty() {
+            if now.duration_since(last_write_time) >= write_frequency_secs && !points.is_empty() {
-                debug!("run: writing {} points", points.len());
+                let num_points = points.len();
+                let points_written;
+                debug!("run: attempting to write {} points", points.len());
+                if points.len() > max_points {
+                    warn!(
+                        "max submission rate of {} datapoints per second exceeded.  only the
+                    first {} of {} points will be submitted",
+                        max_points_per_sec,
+                        max_points,
+                        points.len()
+                    );
+                    points.truncate(max_points - 1);
+                }
+                points_written = points.len();
+
+                points.push(
+                    influxdb::Point::new("metrics")
+                        .add_timestamp(timing::timestamp() as i64)
+                        .add_field("host_id", influxdb::Value::String(HOST_INFO.to_string()))
+                        .add_field(
+                            "points_written",
+                            influxdb::Value::Integer(points_written as i64),
+                        )
+                        .add_field("num_points", influxdb::Value::Integer(num_points as i64))
+                        .add_field(
+                            "secs_since_last_write",
+                            influxdb::Value::Integer(
+                                now.duration_since(last_write_time).as_secs() as i64
+                            ),
+                        )
+                        .add_field(
+                            "points_rate_exceeded",
+                            influxdb::Value::Boolean(num_points > max_points),
+                        )
+                        .to_owned(),
+                );
+
                 writer.write(points);
                 points = Vec::new();
                 last_write_time = now;
@@ -347,7 +393,7 @@ mod test {
     #[test]
     fn test_submit() {
         let writer = Arc::new(MockMetricsWriter::new());
-        let agent = MetricsAgent::new(writer.clone(), Duration::from_secs(10));
+        let agent = MetricsAgent::new(writer.clone(), Duration::from_secs(10), 1000);
 
         for i in 0..42 {
             agent.submit(influxdb::Point::new(&format!("measurement {}", i)));
@@ -360,11 +406,26 @@ mod test {
     #[test]
     fn test_submit_with_delay() {
         let writer = Arc::new(MockMetricsWriter::new());
-        let agent = MetricsAgent::new(writer.clone(), Duration::from_millis(100));
+        let agent = MetricsAgent::new(writer.clone(), Duration::from_secs(1), 1000);
 
         agent.submit(influxdb::Point::new("point 1"));
         thread::sleep(Duration::from_secs(2));
-        assert_eq!(writer.points_written(), 1);
+        assert_eq!(writer.points_written(), 2);
+    }
+
+    #[test]
+    fn test_submit_exceed_max_rate() {
+        let writer = Arc::new(MockMetricsWriter::new());
+        let agent = MetricsAgent::new(writer.clone(), Duration::from_secs(1), 100);
+
+        for i in 0..102 {
+            agent.submit(influxdb::Point::new(&format!("measurement {}", i)));
+        }
+
+        thread::sleep(Duration::from_secs(2));
+
+        agent.flush();
+        assert_eq!(writer.points_written(), 100);
     }
 
     #[test]
@@ -373,6 +434,7 @@ mod test {
         let agent = Arc::new(Mutex::new(MetricsAgent::new(
             writer.clone(),
             Duration::from_secs(10),
+            1000,
         )));
 
         //
@@ -399,7 +461,7 @@ mod test {
     fn test_flush_before_drop() {
         let writer = Arc::new(MockMetricsWriter::new());
         {
-            let agent = MetricsAgent::new(writer.clone(), Duration::from_secs(9999999));
+            let agent = MetricsAgent::new(writer.clone(), Duration::from_secs(9999999), 1000);
             agent.submit(influxdb::Point::new("point 1"));
         }