Scaffolding for problem 06

problem_06/.gitignore

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+/target/
+.idea
+.DS_STORE

problem_06/Cargo.toml

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+[package]
+name = "problem_06"
+version = "0.1.0"
+edition = "2021"
+
+[[bin]]
+name = "server"
+path = "bin/server.rs"
+
+[dependencies]
+bytes = "1"
+tokio = { version = "1", features = ["full"] }
+tracing = "0.1.34"
+tracing-subscriber = { version = "0.3.11", features = ["env-filter"] }

problem_06/src/connection.rs

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+use crate::frame::{self, Frame};
+
+use bytes::{Buf, BytesMut};
+use std::io::Cursor;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, BufWriter};
+use tokio::net::TcpStream;
+use tracing::{debug, info};
+
+#[derive(Debug)]
+pub struct Connection {
+    stream: BufWriter<TcpStream>,
+    buffer: BytesMut,
+}
+
+impl Connection {
+    pub fn new(socket: TcpStream) -> Connection {
+        Connection {
+            stream: BufWriter::new(socket),
+            buffer: BytesMut::with_capacity(4 * 1024),
+        }
+    }
+
+    pub async fn read_frame(&mut self) -> crate::Result<Option<Frame>> {
+        loop {
+            info!("Loop read_frame");
+            if let Some(frame) = self.parse_frame()? {
+                info!("Frame parsed");
+                return Ok(Some(frame));
+            }
+
+            if 0 == self.stream.read_buf(&mut self.buffer).await? {
+                if self.buffer.is_empty() {
+                    return Ok(None);
+                } else {
+                    return Err("connection reset by peer".into());
+                }
+            }
+        }
+    }
+
+    fn parse_frame(&mut self) -> crate::Result<Option<Frame>> {
+        use frame::Error::Incomplete;
+
+        let mut buf = Cursor::new(&self.buffer[..]);
+        debug!(?buf);
+
+        match Frame::check(&mut buf) {
+            Ok(_) => {
+                info!("Frame::check succesful");
+                let len = buf.position() as usize;
+                debug!(?len);
+                buf.set_position(0);
+
+                let frame = Frame::parse(&mut buf)?;
+                self.buffer.advance(len);
+
+                Ok(Some(frame))
+            }
+            Err(Incomplete) => Ok(None),
+            Err(e) => Err(e.into()),
+        }
+    }
+
+    pub async fn write_frame(&mut self, frame: &Frame) -> tokio::io::Result<()> {
+        debug!(?frame);
+        if let Frame::Response(mean) = frame {
+            let _ = self.stream.write_i32(*mean as i32).await?;
+            info!("Write frame Response to stream");
+            return self.stream.flush().await;
+        }
+
+        Ok(())
+    }
+}

problem_06/src/frame.rs

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+use bytes::Buf;
+use std::fmt;
+use std::io::Cursor;
+use std::num::TryFromIntError;
+use std::string::FromUtf8Error;
+use tracing::{debug, error, info};
+
+#[derive(Clone, Debug)]
+pub enum Frame {}
+
+#[derive(Debug)]
+pub enum Error {
+    Incomplete,
+    Other(crate::Error),
+}
+
+impl Frame {
+    pub fn check(src: &mut Cursor<&[u8]>) -> Result<(), Error> {
+        unimplemented!()
+    }
+
+    pub fn parse(src: &mut Cursor<&[u8]>) -> Result<Frame, Error> {
+        unimplemented!()
+    }
+}
+
+fn get_decimal(src: &[u8]) -> Result<i32, Error> {
+    debug!(?src);
+
+    if let Ok(number) = <[u8; 4]>::try_from(src) {
+        return Ok(i32::from_be_bytes(number));
+    };
+
+    Err("protocol error; invalid frame format".into())
+}
+
+fn get_u8(src: &mut Cursor<&[u8]>) -> Result<u8, Error> {
+    if !src.has_remaining() {
+        error!("Incomplete frame");
+        return Err(Error::Incomplete);
+    }
+
+    Ok(src.get_u8())
+}
+
+fn get_line<'a>(src: &mut Cursor<&'a [u8]>) -> Result<&'a [u8], Error> {
+    unimplemented!()
+}
+
+impl From<String> for Error {
+    fn from(src: String) -> Error {
+        Error::Other(src.into())
+    }
+}
+
+impl From<&str> for Error {
+    fn from(src: &str) -> Error {
+        src.to_string().into()
+    }
+}
+
+impl From<FromUtf8Error> for Error {
+    fn from(_src: FromUtf8Error) -> Error {
+        "protocol error; invalid frame format".into()
+    }
+}
+
+impl From<TryFromIntError> for Error {
+    fn from(_src: TryFromIntError) -> Error {
+        "protocol error; invalid frame format".into()
+    }
+}
+
+impl std::error::Error for Error {}
+
+impl fmt::Display for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::Incomplete => "stream ended early".fmt(fmt),
+            Error::Other(err) => err.fmt(fmt),
+        }
+    }
+}

problem_06/src/lib.rs

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+mod connection;
+pub use connection::Connection;
+
+pub mod frame;
+pub use frame::Frame;
+
+pub mod server;
+
+mod shutdown;
+use shutdown::Shutdown;
+
+pub const DEFAULT_PORT: u16 = 1222;
+
+pub type Error = Box<dyn std::error::Error + Send + Sync>;
+pub type Result<T> = std::result::Result<T, Error>;

problem_06/src/server.rs

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+use crate::{frame::Frame, Connection, Shutdown};
+
+use std::collections::BTreeMap;
+use std::future::Future;
+use std::sync::Arc;
+use tokio::net::{TcpListener, TcpStream};
+use tokio::sync::{broadcast, mpsc, Semaphore};
+use tokio::time::{self, Duration};
+use tracing::{debug, error, info};
+
+struct Listener {
+    listener: TcpListener,
+    limit_connections: Arc<Semaphore>,
+    notify_shutdown: broadcast::Sender<()>,
+    shutdown_complete_rx: mpsc::Receiver<()>,
+    shutdown_complete_tx: mpsc::Sender<()>,
+}
+
+struct Handler {
+    connection: Connection,
+    shutdown: Shutdown,
+    local_db: BTreeMap<Timestamp, Price>,
+    _shutdown_complete: mpsc::Sender<()>,
+}
+
+type Timestamp = i32;
+type Price = i32;
+
+const MAX_CONNECTIONS: usize = 5;
+
+pub async fn run(listener: TcpListener, shutdown: impl Future) -> crate::Result<()> {
+    let (notify_shutdown, _) = broadcast::channel(1);
+    let (shutdown_complete_tx, shutdown_complete_rx) = mpsc::channel(1);
+
+    let mut server = Listener {
+        listener,
+        limit_connections: Arc::new(Semaphore::new(MAX_CONNECTIONS)),
+        notify_shutdown,
+        shutdown_complete_tx,
+        shutdown_complete_rx,
+    };
+
+    tokio::select! {
+        res = server.run() => {
+            if let Err(err) = res {
+                error!(cause = %err, "failed to accept");
+            }
+        }
+        _ = shutdown => {
+            info!("shutting down");
+        }
+    }
+
+    let Listener {
+        mut shutdown_complete_rx,
+        shutdown_complete_tx,
+        notify_shutdown,
+        ..
+    } = server;
+
+    drop(notify_shutdown);
+    drop(shutdown_complete_tx);
+
+    let _ = shutdown_complete_rx.recv().await;
+
+    Ok(())
+}
+
+impl Listener {
+    async fn run(&mut self) -> crate::Result<()> {
+        info!("accepting inbound connections");
+
+        loop {
+            let permit = self
+                .limit_connections
+                .clone()
+                .acquire_owned()
+                .await
+                .unwrap();
+
+            let socket = self.accept().await?;
+
+            let mut handler = Handler {
+                connection: Connection::new(socket),
+                shutdown: Shutdown::new(self.notify_shutdown.subscribe()),
+                local_db: BTreeMap::new(),
+                _shutdown_complete: self.shutdown_complete_tx.clone(),
+            };
+
+            info!("Created new handler");
+
+            tokio::spawn(async move {
+                if let Err(err) = handler.run().await {
+                    error!(cause = ?err, "connection error");
+                }
+                drop(permit);
+            });
+        }
+    }
+
+    async fn accept(&mut self) -> crate::Result<TcpStream> {
+        let mut backoff = 1;
+
+        loop {
+            match self.listener.accept().await {
+                Ok((socket, _)) => return Ok(socket),
+                Err(err) => {
+                    if backoff > 64 {
+                        return Err(err.into());
+                    }
+                }
+            }
+
+            time::sleep(Duration::from_secs(backoff)).await;
+
+            backoff *= 2;
+        }
+    }
+}
+
+impl Handler {
+    async fn run(&mut self) -> crate::Result<()> {
+        while !self.shutdown.is_shutdown() {
+            let maybe_frame = tokio::select! {
+                res = self.connection.read_frame() => res?,
+                _ = self.shutdown.recv() => {
+                    debug!("Shutdown");
+                    return Ok(());
+                }
+            };
+
+            debug!(?maybe_frame);
+
+            let frame = match maybe_frame {
+                Some(frame) => frame,
+                None => return Ok(()),
+            };
+        }
+
+        Ok(())
+    }
+}

problem_06/src/shutdown.rs

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+use tokio::sync::broadcast;
+
+#[derive(Debug)]
+pub(crate) struct Shutdown {
+    shutdown: bool,
+    notify: broadcast::Receiver<()>,
+}
+
+impl Shutdown {
+    pub(crate) fn new(notify: broadcast::Receiver<()>) -> Shutdown {
+        Shutdown {
+            shutdown: false,
+            notify,
+        }
+    }
+
+    pub(crate) fn is_shutdown(&self) -> bool {
+        self.shutdown
+    }
+
+    pub(crate) async fn recv(&mut self) {
+        if self.shutdown {
+            return;
+        }
+
+        let _ = self.notify.recv().await;
+
+        self.shutdown = true;
+    }
+}