From 841987142882df300547d3efb99d2550eb33970f Mon Sep 17 00:00:00 2001
From: _ <_@_>
Date: Wed, 28 Apr 2021 19:50:40 -0500
Subject: [PATCH] :construction: wip: testing a hypothesis about collecting
 metrics

---
 Cargo.lock                      |  14 ++++
 crates/metrics_test/Cargo.toml  |  11 +++
 crates/metrics_test/src/main.rs | 130 ++++++++++++++++++++++++++++++++
 3 files changed, 155 insertions(+)
 create mode 100644 crates/metrics_test/Cargo.toml
 create mode 100644 crates/metrics_test/src/main.rs

diff --git a/Cargo.lock b/Cargo.lock
index fe92ba9..1f502c4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -425,6 +425,12 @@ dependencies = [
  "tracing-subscriber",
 ]
 
+[[package]]
+name = "devtimer"
+version = "4.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "907339959a92f6b98846570500c0a567c9aecbb3871cef00561eb5d20d47b7c1"
+
 [[package]]
 name = "digest"
 version = "0.8.1"
@@ -1053,6 +1059,14 @@ version = "2.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0ee1c47aaa256ecabcaea351eae4a9b01ef39ed810004e298d2511ed284b1525"
 
+[[package]]
+name = "metrics_test"
+version = "0.1.0"
+dependencies = [
+ "devtimer",
+ "tokio",
+]
+
 [[package]]
 name = "mime"
 version = "0.3.16"
diff --git a/crates/metrics_test/Cargo.toml b/crates/metrics_test/Cargo.toml
new file mode 100644
index 0000000..fef35f8
--- /dev/null
+++ b/crates/metrics_test/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "metrics_test"
+version = "0.1.0"
+authors = ["_ <_@_>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+devtimer = "4.0.1"
+tokio = { version = "1.4.0", features = ["full"] }
diff --git a/crates/metrics_test/src/main.rs b/crates/metrics_test/src/main.rs
new file mode 100644
index 0000000..abe3bf7
--- /dev/null
+++ b/crates/metrics_test/src/main.rs
@@ -0,0 +1,130 @@
+use std::{
+	sync::{
+		Arc,
+	},
+	time::Duration,
+};
+
+use devtimer::DevTime;
+use tokio::{
+	sync::{
+		RwLock,
+		mpsc,
+	},
+};
+
+#[tokio::main]
+async fn main () {
+	let num_iters = 1_000_000;
+	let mut timer = DevTime::new_simple ();
+	
+	let metric_lock = MetricLock::default ();
+	
+	timer.start ();
+	for _ in 0..num_iters {
+		metric_lock.add (10).await;
+	}
+	timer.stop ();
+	println!("The operation took: {} milliseconds", timer.time_in_millis().unwrap());
+	
+	assert_eq! (metric_lock.read ().await, Counter {
+		count: num_iters,
+		time: 10 * num_iters,
+	});
+	
+	// This is about 4 times slower with a single thread sending
+	// events. Also they're both faster enough that I don't care.
+	
+	let metric_channel = MetricChannel::new ();
+	
+	timer.start ();
+	for _ in 0..num_iters {
+		metric_channel.add (10_u64).await;
+	}
+	timer.stop ();
+	println!("The operation took: {} milliseconds", timer.time_in_millis().unwrap());
+	
+	tokio::time::sleep (Duration::from_millis (100)).await;
+	
+	assert_eq! (metric_channel.read ().await, Counter {
+		count: num_iters,
+		time: 10 * num_iters,
+	});
+}
+
+#[derive (Default)]
+struct MetricLock {
+	counter: RwLock <Counter>,
+}
+
+impl MetricLock {
+	async fn add (&self, time: u64) {
+		let mut guard = self.counter.write ().await;
+		guard.add (time);
+	}
+	
+	async fn read (&self) -> Counter {
+		let guard = self.counter.read ().await;
+		*guard
+	}
+}
+
+struct MetricChannel {
+	counter: RwLock <Counter>,
+	sender: mpsc::Sender <u64>,
+}
+
+impl MetricChannel {
+	fn new () -> Arc <Self> {
+		let counter = Default::default ();
+		let (sender, mut receiver) = mpsc::channel (64);
+		
+		let mc = Self {
+			counter, 
+			sender,
+		};
+		let mc = Arc::new (mc);
+		
+		{
+			let mc = Arc::clone (&mc);
+			tokio::spawn (async move {
+				let mut unflushed = Counter::default ();
+				
+				while let Some (time) = receiver.recv ().await {
+					unflushed.add (time);
+					
+					if unflushed.count >= 10 {
+						let mut guard = mc.counter.write ().await;
+						guard.count += unflushed.count;
+						guard.time += unflushed.time;
+						unflushed = Counter::default ();
+					}
+				}
+			});
+		}
+		
+		mc
+	}
+	
+	async fn add (&self, time: u64) {
+		self.sender.send (time).await.unwrap ()
+	}
+	
+	async fn read (&self) -> Counter {
+		let guard = self.counter.read ().await;
+		*guard
+	}
+}
+
+#[derive (Copy, Clone, Debug, Default, PartialEq)]
+struct Counter {
+	count: u64,
+	time: u64,
+}
+
+impl Counter {
+	fn add (&mut self, time: u64) {
+		self.count += 1;
+		self.time += time;
+	}
+}