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318 lines
9.5 KiB
Rust
318 lines
9.5 KiB
Rust
use std::collections::HashMap;
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use std::sync::{Arc, Weak};
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use std::time::Duration;
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use async_trait::async_trait;
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use tokio::sync::{mpsc, Mutex, RwLock};
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use tokio::{io, time};
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use crate::common::{Id, Response, UntypedResponse};
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#[derive(Clone, Debug)]
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pub struct PostOffice<T> {
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mailboxes: Arc<Mutex<HashMap<Id, mpsc::Sender<T>>>>,
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default_box: Arc<RwLock<Option<mpsc::Sender<T>>>>,
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}
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impl<T> Default for PostOffice<T>
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where
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T: Send + 'static,
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{
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/// Creates a new postoffice with a cleanup interval of 60s
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fn default() -> Self {
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Self::new(Duration::from_secs(60))
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}
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}
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impl<T> PostOffice<T>
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where
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T: Send + 'static,
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{
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/// Creates a new post office that delivers to mailboxes, cleaning up orphaned mailboxes
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/// waiting `cleanup` time inbetween attempts
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pub fn new(cleanup: Duration) -> Self {
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let mailboxes = Arc::new(Mutex::new(HashMap::new()));
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let mref = Arc::downgrade(&mailboxes);
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// Spawn a task that will clean up orphaned mailboxes every minute
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tokio::spawn(async move {
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while let Some(m) = Weak::upgrade(&mref) {
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m.lock()
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.await
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.retain(|_id, tx: &mut mpsc::Sender<T>| !tx.is_closed());
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// NOTE: Must drop the reference before sleeping, otherwise we block
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// access to the mailbox map elsewhere and deadlock!
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drop(m);
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// Wait a minute before trying again
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time::sleep(cleanup).await;
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}
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});
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Self {
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mailboxes,
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default_box: Arc::new(RwLock::new(None)),
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}
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}
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/// Creates a new mailbox using the given id and buffer size for maximum values that
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/// can be queued in the mailbox
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pub async fn make_mailbox(&self, id: Id, buffer: usize) -> Mailbox<T> {
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let (tx, rx) = mpsc::channel(buffer);
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self.mailboxes.lock().await.insert(id.clone(), tx);
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Mailbox {
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id,
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rx: Box::new(rx),
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}
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}
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/// Delivers some value to appropriate mailbox, returning false if no mailbox is found
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/// for the specified id or if the mailbox is no longer receiving values
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pub async fn deliver(&self, id: &Id, value: T) -> bool {
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if let Some(tx) = self.mailboxes.lock().await.get_mut(id) {
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let success = tx.send(value).await.is_ok();
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// If failed, we want to remove the mailbox sender as it is no longer valid
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if !success {
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self.mailboxes.lock().await.remove(id);
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}
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success
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} else if let Some(tx) = self.default_box.read().await.as_ref() {
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tx.send(value).await.is_ok()
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} else {
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false
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}
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}
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/// Creates a new default mailbox that will be used whenever no mailbox is found to deliver
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/// mail. This will replace any existing default mailbox.
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pub async fn assign_default_mailbox(&self, buffer: usize) -> Mailbox<T> {
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let (tx, rx) = mpsc::channel(buffer);
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*self.default_box.write().await = Some(tx);
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Mailbox {
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id: "".to_string(),
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rx: Box::new(rx),
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}
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}
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/// Removes the default mailbox such that any mail without a matching mailbox will be dropped
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/// instead of being delivered to a default mailbox.
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pub async fn remove_default_mailbox(&self) {
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*self.default_box.write().await = None;
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}
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/// Returns true if the post office is using a default mailbox for all mail that does not map
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/// to another mailbox.
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pub async fn has_default_mailbox(&self) -> bool {
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self.default_box.read().await.is_some()
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}
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/// Cancels delivery to the mailbox with the specified `id`.
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pub async fn cancel(&self, id: &Id) {
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self.mailboxes.lock().await.remove(id);
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}
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/// Cancels delivery to the mailboxes with the specified `id`s.
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pub async fn cancel_many(&self, ids: impl Iterator<Item = &Id>) {
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let mut lock = self.mailboxes.lock().await;
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for id in ids {
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lock.remove(id);
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}
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}
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/// Cancels delivery to all mailboxes.
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pub async fn cancel_all(&self) {
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self.mailboxes.lock().await.clear();
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}
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}
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impl<T> PostOffice<Response<T>>
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where
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T: Send + 'static,
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{
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/// Delivers some response to appropriate mailbox, returning false if no mailbox is found
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/// for the response's origin or if the mailbox is no longer receiving values
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pub async fn deliver_response(&self, res: Response<T>) -> bool {
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self.deliver(&res.origin_id.clone(), res).await
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}
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}
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impl PostOffice<UntypedResponse<'static>> {
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/// Delivers some response to appropriate mailbox, returning false if no mailbox is found
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/// for the response's origin or if the mailbox is no longer receiving values
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pub async fn deliver_untyped_response(&self, res: UntypedResponse<'static>) -> bool {
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self.deliver(&res.origin_id.clone().into_owned(), res).await
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}
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}
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/// Error encountered when invoking [`try_recv`] for [`MailboxReceiver`].
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pub enum MailboxTryNextError {
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Empty,
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Closed,
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}
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#[async_trait]
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trait MailboxReceiver: Send + Sync {
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type Output;
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fn try_recv(&mut self) -> Result<Self::Output, MailboxTryNextError>;
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async fn recv(&mut self) -> Option<Self::Output>;
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fn close(&mut self);
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}
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#[async_trait]
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impl<T: Send> MailboxReceiver for mpsc::Receiver<T> {
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type Output = T;
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fn try_recv(&mut self) -> Result<Self::Output, MailboxTryNextError> {
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match mpsc::Receiver::try_recv(self) {
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Ok(x) => Ok(x),
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Err(mpsc::error::TryRecvError::Empty) => Err(MailboxTryNextError::Empty),
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Err(mpsc::error::TryRecvError::Disconnected) => Err(MailboxTryNextError::Closed),
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}
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}
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async fn recv(&mut self) -> Option<Self::Output> {
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mpsc::Receiver::recv(self).await
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}
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fn close(&mut self) {
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mpsc::Receiver::close(self)
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}
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}
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struct MappedMailboxReceiver<T, U> {
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rx: Box<dyn MailboxReceiver<Output = T>>,
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f: Box<dyn Fn(T) -> U + Send + Sync>,
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}
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#[async_trait]
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impl<T: Send, U: Send> MailboxReceiver for MappedMailboxReceiver<T, U> {
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type Output = U;
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fn try_recv(&mut self) -> Result<Self::Output, MailboxTryNextError> {
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match self.rx.try_recv() {
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Ok(x) => Ok((self.f)(x)),
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Err(x) => Err(x),
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}
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}
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async fn recv(&mut self) -> Option<Self::Output> {
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let value = self.rx.recv().await?;
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Some((self.f)(value))
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}
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fn close(&mut self) {
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self.rx.close()
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}
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}
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struct MappedOptMailboxReceiver<T, U> {
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rx: Box<dyn MailboxReceiver<Output = T>>,
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f: Box<dyn Fn(T) -> Option<U> + Send + Sync>,
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}
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#[async_trait]
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impl<T: Send, U: Send> MailboxReceiver for MappedOptMailboxReceiver<T, U> {
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type Output = U;
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fn try_recv(&mut self) -> Result<Self::Output, MailboxTryNextError> {
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match self.rx.try_recv() {
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Ok(x) => match (self.f)(x) {
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Some(x) => Ok(x),
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None => Err(MailboxTryNextError::Empty),
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},
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Err(x) => Err(x),
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}
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}
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async fn recv(&mut self) -> Option<Self::Output> {
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// Continually receive a new value and convert it to Option<U>
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// until Option<U> == Some(U) or we receive None from our inner receiver
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loop {
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let value = self.rx.recv().await?;
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if let Some(x) = (self.f)(value) {
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return Some(x);
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}
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}
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}
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fn close(&mut self) {
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self.rx.close()
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}
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}
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/// Represents a destination for responses
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pub struct Mailbox<T> {
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/// Represents id associated with the mailbox
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id: Id,
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/// Underlying mailbox storage
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rx: Box<dyn MailboxReceiver<Output = T>>,
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}
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impl<T> Mailbox<T> {
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/// Represents id associated with the mailbox
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pub fn id(&self) -> &Id {
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&self.id
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}
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/// Tries to receive the next value in mailbox without blocking or waiting async
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pub fn try_next(&mut self) -> Result<T, MailboxTryNextError> {
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self.rx.try_recv()
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}
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/// Receives next value in mailbox
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pub async fn next(&mut self) -> Option<T> {
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self.rx.recv().await
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}
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/// Receives next value in mailbox, waiting up to duration before timing out
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pub async fn next_timeout(&mut self, duration: Duration) -> io::Result<Option<T>> {
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time::timeout(duration, self.next())
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.await
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.map_err(|x| io::Error::new(io::ErrorKind::TimedOut, x))
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}
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/// Closes the mailbox such that it will not receive any more values
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///
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/// Any values already in the mailbox will still be returned via `next`
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pub fn close(&mut self) {
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self.rx.close()
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}
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}
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impl<T: Send + 'static> Mailbox<T> {
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/// Maps the results of each mailbox value into a new type `U`
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pub fn map<U: Send + 'static>(self, f: impl Fn(T) -> U + Send + Sync + 'static) -> Mailbox<U> {
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Mailbox {
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id: self.id,
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rx: Box::new(MappedMailboxReceiver {
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rx: self.rx,
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f: Box::new(f),
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}),
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}
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}
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/// Maps the results of each mailbox value into a new type `U` by returning an `Option<U>`
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/// where the option is `None` in the case that `T` cannot be converted into `U`
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pub fn map_opt<U: Send + 'static>(
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self,
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f: impl Fn(T) -> Option<U> + Send + Sync + 'static,
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) -> Mailbox<U> {
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Mailbox {
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id: self.id,
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rx: Box::new(MappedOptMailboxReceiver {
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rx: self.rx,
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f: Box::new(f),
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}),
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}
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}
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}
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