improvements phase: toy -> med

Cargo.lock

@@ -66,6 +66,21 @@ version = "1.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33"
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "82b8f8f868b36967f9606790d1903570de9ceaf870a7bf9fbbd3016d636a2cb2"
+dependencies = [
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0a5c400df2834b80a4c3327b3aad3a4c4cd4de0629063962b03235697506a28"
+
 [[package]]
 name = "errno"
 version = "0.3.14"
@@ -375,6 +390,7 @@ name = "simple-tsdb"
 version = "0.1.0"
 dependencies = [
  "axum",
+ "crossbeam-channel",
  "serde",
  "serde_json",
  "tokio",

Cargo.toml

@@ -7,4 +7,5 @@ edition = "2024"
 tokio = { version = "1.50.0", features = ["signal", "rt", "rt-multi-thread", "macros"] }
 axum = "0.8.8"
 serde = { version = "1.0.228", features = ["derive"] }
-serde_json = "1.0.149"
+serde_json = "1.0.149"
+crossbeam-channel = "0.5.15"

scripts/test/send.lua

@@ -0,0 +1,7 @@
+wrk.method = "POST"
+wrk.headers["Content-Type"] = "application/json"
+
+function request()
+  local body = '{"metric":"cpu_usage","timestamp":' .. os.time() .. ',"value":42.3}'
+  return wrk.format(nil, "/metrics", nil, body)
+end

scripts/test/send.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -euo pipefail
+
+THREADS=${1:-4}
+CONNECTIONS=${2:-10}
+DURATION_SECS=${3:-30}
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+wrk -t"$THREADS" -c"$CONNECTIONS" -d"$DURATION_SECS"s -s "$SCRIPT_DIR/send.lua" http://localhost:3000

scripts/test/spawn.sh

@@ -23,7 +23,7 @@ cleanup() {
   echo "All workers stopped."
 }
 
-trap cleanup SIGINT SIGTERM EXIT
+trap cleanup SIGINT SIGTERM
 
 echo "Starting $THREADS workers with RATE=$RATE each..."
 

src/main.rs

@@ -1,14 +1,19 @@
 use axum::extract::State;
+use axum::http::StatusCode;
 use axum::{
     extract::Json,
     routing::post,
     Router,
 };
+use crossbeam_channel::{bounded, Receiver, RecvTimeoutError, Sender};
 use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::fs::{File, OpenOptions};
-use std::io::{BufRead, BufReader, Write};
-use std::sync::{Arc, Mutex};
+use std::io::{BufRead, BufReader, BufWriter, Write};
+use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
+use std::sync::Arc;
+use std::thread;
+use std::thread::JoinHandle;
 use std::time::Duration;
 use tokio::net::TcpListener;
 use tokio::signal;
@@ -20,60 +25,166 @@ struct Metric {
     value: f64,
 }
 
+enum QueueCommand {
+    WriteLine(String),
+    Shutdown,
+}
+
 #[derive(Clone)]
 struct BaseState {
-    file: Arc<Mutex<File>>,
+    sender: Sender<QueueCommand>,
+    queue_size: Arc<AtomicUsize>,
+    running: Arc<AtomicBool>,
 }
 
 impl BaseState {
-    fn new(file: File) -> Self {
+    fn new(sender: Sender<QueueCommand>) -> Self {
         BaseState {
-            file: Arc::new(Mutex::new(file)),
+            sender,
+            queue_size: Arc::new(AtomicUsize::new(0)),
+            running: Arc::new(AtomicBool::new(true)),
         }
     }
 }
 
 #[tokio::main]
 async fn main() {
+    let (tx, rx) = bounded::<QueueCommand>(1000);
+    let state = BaseState::new(tx.clone());
+    println!("Starting Simple TSDB... listening on: localhost <port: 3000>");
+
+    let writer = spawn_writer_facade(rx, &state);
+    let counter = spawn_counter_facade(&state);
+
+    let app = Router::new().route("/metrics", post(handler)).with_state(state.clone());
+    let listener = TcpListener::bind("0.0.0.0:3000").await.expect("error when opening port 3000");
+
+    let start_time = std::time::SystemTime::now();
+    axum::serve(listener, app).with_graceful_shutdown(shutdown_signal(state.clone())).await.expect("internal server error");
+
+    writer.join().expect("error thread panic");
+    counter.join().expect("error thread panic");
+    println!("\nServer Stopped. Analysing metrics...\n");
+    let elapsed = start_time.elapsed().expect("error when measuring elapsed time");
+    print_metrics_report(elapsed, "data/metrics.ndjson");
+}
+
+fn spawn_counter_facade(state: &BaseState) -> JoinHandle<()> {
+    let s2 = state.clone();
+    let counter = thread::spawn(move || counter_facade(s2));
+    counter
+}
+
+fn counter_facade(state: BaseState) {
+    let spinner = ['⠁','⠂','⠄','⡀','⢀','⠠','⠐','⠈'];
+    let mut i = 0;
+
+    while state.running.load(Ordering::Relaxed)
+    {
+        let size = state.queue_size.load(Ordering::Relaxed);
+        let spin = spinner[i % spinner.len()];
+        print!("\r\x1b[2K{} pending_writes: {:5}", spin, size);
+        std::io::stdout().flush().unwrap();
+
+        i += 1;
+        thread::sleep(Duration::from_millis(80));
+    }
+
+    println!("\r\x1b[2K✔ done");
+}
+
+fn spawn_writer_facade(rx: Receiver<QueueCommand>, state: &BaseState) -> JoinHandle<()> {
+    let s1 = state.clone();
+    let writer = thread::spawn(move || writer_facade(s1, rx));
+    writer
+}
+
+fn writer_facade(state: BaseState, rx: Receiver<QueueCommand>) {
+    std::fs::create_dir_all("data").expect("error when creating data dir");
     let file = OpenOptions::new()
         .append(true)
         .create(true)
         .open("data/metrics.ndjson")
         .expect("error when opening file");
-    let state = BaseState::new(file);
-    let app = Router::new().route("/metrics", post(receive_metric)).with_state(state.clone());
-    let listener = TcpListener::bind("0.0.0.0:3000").await.expect("error when opening port 3000");
-    println!("Starting Simple TSDB... listening on: localhost <port: 3000>");
+    let mut writer = BufWriter::new(file);
 
-    let start_time = std::time::SystemTime::now();
-    axum::serve(listener, app).with_graceful_shutdown(shutdown_signal()).await.expect("internal server error");
+    let buffer_flush = |writer: &mut BufWriter<File>, buffer: &mut Vec<String>| -> usize {
+        let amount = buffer.len();
+        if amount <= 0 {
+            return 0usize;
+        }
 
-    {
-        let mut file = state.file.lock().expect("error when locking file");
-        file.flush().expect("error when final flushing");
+        for line in buffer.drain(..) {
+            writer.write_all(line.as_bytes()).unwrap();
+            writer.write_all(b"\n").unwrap();
+        }
+
+        // thread::sleep(Duration::from_millis(20)); // delay of 20ms - simulate ~50ops/s
+        amount
+    };
+
+    let flush_writer = |writer: &mut BufWriter<File>| {
+        writer.flush().expect("error when flushing writer");
+    };
+
+    let shutdown = |writer: &mut BufWriter<File>, buffer: &mut Vec<String>| {
+        state.running.store(false, Ordering::Relaxed);
+        let amount = buffer_flush(writer, buffer);
+        state.queue_size.fetch_sub(amount, Ordering::Relaxed);
+        flush_writer(writer);
+    };
+
+    let buffer_capacity = 50;
+    let mut buffer: Vec<String> = Vec::with_capacity(buffer_capacity);
+
+    loop {
+        match rx.recv_timeout(Duration::from_millis(100)) {
+            Ok(QueueCommand::WriteLine(line)) => {
+                buffer.push(line);
+                if buffer.len() >= buffer_capacity {
+                    let amount = buffer_flush(&mut writer, &mut buffer);
+                    state.queue_size.fetch_sub(amount, Ordering::Relaxed);
+                }
+            }
+            Err(RecvTimeoutError::Timeout) => {
+                if !buffer.is_empty() {
+                    let amount = buffer_flush(&mut writer, &mut buffer);
+                    state.queue_size.fetch_sub(amount, Ordering::Relaxed);
+                }
+            }
+            Ok(QueueCommand::Shutdown) => {
+                println!("\nStarting shutdown...");
+                shutdown(&mut writer, &mut buffer);
+                break; // quit the loop
+            }
+            Err(RecvTimeoutError::Disconnected) => {
+                println!("error when receiving command: disconnected");
+                shutdown(&mut writer, &mut buffer);
+                break; // quit the loop
+            }
+        }
     }
-
-    let elapsed = start_time.elapsed().expect("error when measuring elapsed time");
-    println!("\nStoping server. Analysing metrics...\n");
-    print_metrics_report(elapsed, "data/metrics.ndjson");
 }
 
-async fn receive_metric(
+async fn handler(
     State(state): State<BaseState>,
-    Json(metric): Json<Metric>) -> &'static str {
-    println!("metric received: {:?}", metric);
-
+    Json(metric): Json<Metric>) -> StatusCode {
     let line = serde_json::to_string(&metric).expect("error when serializing metric");
-
-    let mut file = state.file.lock().expect("error when locking file");
-    writeln!(file, "{line}").expect("error when writing to file");
-
-    "ok"
+    state.queue_size.fetch_add(1, Ordering::Relaxed);
+    match state.sender.try_send(QueueCommand::WriteLine(line)) {
+        Ok(_) => {
+            StatusCode::OK
+        },
+        Err(_) => {
+            state.queue_size.fetch_sub(1, Ordering::Relaxed);
+            StatusCode::SERVICE_UNAVAILABLE
+        },
+    }
 }
 
-async fn shutdown_signal() {
+async fn shutdown_signal(state: BaseState) {
     signal::ctrl_c().await.expect("fail when waiting for Ctrl+C");
-    println!("\nCtrl+C ack. Starting shutdown...");
+    state.sender.send(QueueCommand::Shutdown).expect("error when sending flush signal");
 }
 
 fn print_metrics_report(elapsed: Duration, path: &str) {
@@ -115,8 +226,8 @@ fn print_metrics_report(elapsed: Duration, path: &str) {
         return;
     }
 
-    let elapsed_time = elapsed.as_secs();
-    let rate = total as f64 / elapsed_time as f64;
+    let elapsed_time = elapsed.as_secs_f64().max(0.001);
+    let rate = total as f64 / elapsed_time;
     println!("Number of valid metrics: {total} in {elapsed_time}s ({rate} metrics/s)");
     if invalid_lines > 0 {
         println!("Ignored values: {invalid_lines}");