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// Copyright 2019-2021 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any
// person obtaining a copy of this software and associated
// documentation files (the "Software"), to deal in the
// Software without restriction, including without
// limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software
// is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice
// shall be included in all copies or substantial portions
// of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
use crate::{error::SubscriptionClosedError, v2::SubscriptionId, Error};
use core::marker::PhantomData;
use futures_channel::{mpsc, oneshot};
use futures_util::{future::FutureExt, sink::SinkExt, stream::StreamExt};
use serde::{de::DeserializeOwned, Deserialize, Serialize};
use serde_json::Value as JsonValue;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;
/// Subscription kind
#[derive(Debug)]
#[non_exhaustive]
pub enum SubscriptionKind {
/// Get notifications based on Subscription ID.
Subscription(SubscriptionId),
/// Get notifications based on method name.
Method(String),
/// Internal type to detect whether a subscription response from
/// the server was a valid notification or should be treated as an error.
#[derive(Debug, Deserialize, Serialize)]
#[serde(untagged)]
enum NotifResponse<Notif> {
Ok(Notif),
Err(SubscriptionClosedError),
}
/// Active subscription on the client.
///
/// It will automatically unsubscribe in the [`Subscription::drop`] so no need to explicitly call
/// the `unsubscribe method` if it is an an subscription based on [`SubscriptionId`].
#[derive(Debug)]
pub struct Subscription<Notif> {
/// Channel to send requests to the background task.
to_back: mpsc::Sender<FrontToBack>,
/// Channel from which we receive notifications from the server, as encoded `JsonValue`s.
notifs_rx: mpsc::Receiver<JsonValue>,
/// Callback kind.
kind: SubscriptionKind,
/// Marker in order to pin the `Notif` parameter.
marker: PhantomData<Notif>,
}
impl<Notif> Subscription<Notif> {
/// Create a new subscription.
pub fn new(
to_back: mpsc::Sender<FrontToBack>,
notifs_rx: mpsc::Receiver<JsonValue>,
kind: SubscriptionKind,
) -> Self {
Self { to_back, notifs_rx, kind, marker: PhantomData }
}
/// Batch request message.
#[derive(Debug)]
pub struct BatchMessage {
/// Serialized batch request.
pub raw: String,
/// Request IDs.
pub ids: Vec<u64>,
/// One-shot channel over which we send back the result of this request.
pub send_back: oneshot::Sender<Result<Vec<JsonValue>, Error>>,
}
/// Request message.
#[derive(Debug)]
pub struct RequestMessage {
/// Serialized message.
pub raw: String,
/// Request ID.
pub id: u64,
/// One-shot channel over which we send back the result of this request.
pub send_back: Option<oneshot::Sender<Result<JsonValue, Error>>>,
}
/// Subscription message.
#[derive(Debug)]
pub struct SubscriptionMessage {
/// Serialized message.
pub raw: String,
/// Request ID of the subscribe message.
pub subscribe_id: u64,
/// Request ID of the unsubscribe message.
pub unsubscribe_id: u64,
/// Method to use to unsubscribe later. Used if the channel unexpectedly closes.
pub unsubscribe_method: String,
/// If the subscription succeeds, we return a [`mpsc::Receiver`] that will receive notifications.
/// When we get a response from the server about that subscription, we send the result over
/// this channel.
pub send_back: oneshot::Sender<Result<(mpsc::Receiver<JsonValue>, SubscriptionId), Error>>,
}
/// RegisterNotification message.
#[derive(Debug)]
pub struct RegisterNotificationMessage {
/// Method name this notification handler is attached to
pub method: String,
/// We return a [`mpsc::Receiver`] that will receive notifications.
/// When we get a response from the server about that subscription, we send the result over
/// this channel.
pub send_back: oneshot::Sender<Result<(mpsc::Receiver<JsonValue>, String), Error>>,
}
/// Message that the Client can send to the background task.
pub enum FrontToBack {
/// Send a batch request to the server.
Batch(BatchMessage),
/// Send a notification to the server.
/// Send a request to the server.
/// Send a subscription request to the server.
Subscribe(SubscriptionMessage),
/// Register a notification handler
RegisterNotification(RegisterNotificationMessage),
/// Unregister a notification handler
UnregisterNotification(String),
/// When a subscription channel is closed, we send this message to the background
/// task to mark it ready for garbage collection.
// NOTE: It is not possible to cancel pending subscriptions or pending requests.
// Such operations will be blocked until a response is received or the background
// thread has been terminated.
SubscriptionClosed(SubscriptionId),
}
impl<Notif> Subscription<Notif>
where
Notif: DeserializeOwned,
{
/// Returns the next notification from the stream.
/// This may return `Ok(None)` if the subscription has been terminated,
/// may happen if the channel becomes full or is dropped.
pub async fn next(&mut self) -> Result<Option<Notif>, Error> {
match self.notifs_rx.next().await {
Some(n) => match serde_json::from_value::<NotifResponse<Notif>>(n) {
Ok(NotifResponse::Ok(parsed)) => Ok(Some(parsed)),
Ok(NotifResponse::Err(e)) => Err(Error::SubscriptionClosed(e)),
Err(e) => Err(Error::ParseError(e)),
},
None => Ok(None),
impl<Notif> Drop for Subscription<Notif> {
fn drop(&mut self) {
// We can't actually guarantee that this goes through. If the background task is busy, then
// the channel's buffer will be full.
// However, when a notification arrives, the background task will realize that the channel
// to the `Callback` has been closed.
let kind = std::mem::replace(&mut self.kind, SubscriptionKind::Subscription(SubscriptionId::Num(0)));
let msg = match kind {
SubscriptionKind::Method(notif) => FrontToBack::UnregisterNotification(notif),
SubscriptionKind::Subscription(sub_id) => FrontToBack::SubscriptionClosed(sub_id),
};
let _ = self.to_back.send(msg).now_or_never();
#[derive(Debug)]
/// Keep track of request IDs.
pub struct RequestIdManager {
// Current pending requests.
/// Max concurrent pending requests allowed.
max_concurrent_requests: usize,
/// Get the next request ID.
current_id: AtomicU64,
}
/// Create a new `RequestIdGuard` with the provided concurrency limit.
pub fn new(limit: usize) -> Self {
Self { current_pending: Arc::new(()), max_concurrent_requests: limit, current_id: AtomicU64::new(0) }
fn get_slot(&self) -> Result<Arc<()>, Error> {
// Strong count is 1 at start, so that's why we use `>` and not `>=`.
if Arc::strong_count(&self.current_pending) > self.max_concurrent_requests {
Err(Error::MaxSlotsExceeded)
} else {
Ok(self.current_pending.clone())
}
}
/// Attempts to get the next request ID.
///
/// Fails if request limit has been exceeded.
pub fn next_request_id(&self) -> Result<RequestIdGuard<u64>, Error> {
let rc = self.get_slot()?;
let id = self.current_id.fetch_add(1, Ordering::SeqCst);
Ok(RequestIdGuard { _rc: rc, id })
}
/// Attempts to get the `n` number next IDs that only counts as one request.
///
/// Fails if request limit has been exceeded.
pub fn next_request_ids(&self, len: usize) -> Result<RequestIdGuard<Vec<u64>>, Error> {
let rc = self.get_slot()?;
let mut ids = Vec::with_capacity(len);
for _ in 0..len {
ids.push(self.current_id.fetch_add(1, Ordering::SeqCst));
Ok(RequestIdGuard { _rc: rc, id: ids })
}
}
/// Reference counted request ID.
#[derive(Debug)]
pub struct RequestIdGuard<T> {
id: T,
/// Reference count decreased when dropped.
_rc: Arc<()>,
}
impl<T> RequestIdGuard<T> {
/// Get the actual ID.
pub fn inner(&self) -> &T {
&self.id
}
#[cfg(test)]
mod tests {
use super::RequestIdManager;
#[test]
fn request_id_guard_works() {
let manager = RequestIdManager::new(2);
let _first = manager.next_request_id().unwrap();
{
let _second = manager.next_request_ids(13).unwrap();
assert!(manager.next_request_id().is_err());
// second dropped here.
}
assert!(manager.next_request_id().is_ok());
/// What certificate store to use
#[derive(Clone, Copy, Debug, PartialEq)]
#[non_exhaustive]
pub enum CertificateStore {
/// Use the native system certificate store
Native,
/// Use WebPKI's certificate store
WebPki,
}