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//! NATS client
//!
//! [`NatsClient`] provided here is a wrapper around [`Client`] that provides convenient methods
//! using domain-specific traits.
//!
//! Before reading code, make sure to familiarize yourself with NATS documentation, especially with
//! [subjects](https://docs.nats.io/nats-concepts/subjects) and
//! [Core NATS](https://docs.nats.io/nats-concepts/core-nats) features.
//!
//! Abstractions provided here cover a few use cases:
//! * request/response (for example piece request)
//! * request/stream of responses (for example a stream of plotted sectors of the farmer)
//! * notifications (typically targeting a particular instance of an app) and corresponding subscriptions (for example solution notification)
//! * broadcasts and corresponding subscriptions (for example slot info broadcast)
use crate::utils::AsyncJoinOnDrop;
use anyhow::anyhow;
use async_nats::{
Client, ConnectOptions, HeaderMap, HeaderValue, Message, PublishError, RequestError,
RequestErrorKind, Subject, SubscribeError, Subscriber, ToServerAddrs,
};
use backoff::backoff::Backoff;
use backoff::ExponentialBackoff;
use derive_more::{Deref, DerefMut};
use futures::channel::mpsc;
use futures::stream::FuturesUnordered;
use futures::{select, FutureExt, Stream, StreamExt};
use parity_scale_codec::{Decode, Encode};
use std::any::type_name;
use std::collections::VecDeque;
use std::future::{pending, Future};
use std::marker::PhantomData;
use std::pin::Pin;
use std::sync::Arc;
use std::task::{Context, Poll};
use std::time::Duration;
use std::{fmt, mem};
use thiserror::Error;
use tracing::{debug, error, trace, warn, Instrument};
use ulid::Ulid;
const EXPECTED_MESSAGE_SIZE: usize = 2 * 1024 * 1024;
const ACKNOWLEDGEMENT_TIMEOUT: Duration = Duration::from_mins(1);
/// Requests should time out eventually, but we should set a larger timeout to allow for spikes in
/// load to be absorbed gracefully
const REQUEST_TIMEOUT: Duration = Duration::from_mins(5);
/// Generic request with associated response.
///
/// Used for cases where request/response pattern is needed and response contains a single small
/// message. For large messages or multiple messages chunking with [`GenericStreamRequest`] can be
/// used instead.
pub trait GenericRequest: Encode + Decode + fmt::Debug + Send + Sync + 'static {
/// Request subject with optional `*` in place of application instance to receive the request
const SUBJECT: &'static str;
/// Response type that corresponds to this request
type Response: Encode + Decode + fmt::Debug + Send + Sync + 'static;
}
/// Generic stream request where response is streamed using [`NatsClient::stream_response`].
///
/// Used for cases where a large payload that doesn't fit into NATS message needs to be sent or
/// there is a very large number of messages to send. For simple request/response patten
/// [`GenericRequest`] can be used instead.
pub trait GenericStreamRequest: Encode + Decode + fmt::Debug + Send + Sync + 'static {
/// Request subject with optional `*` in place of application instance to receive the request
const SUBJECT: &'static str;
/// Response type that corresponds to this stream request. These responses are send as a stream
/// of [`GenericStreamResponses`] messages.
type Response: Encode + Decode + fmt::Debug + Send + Sync + 'static;
}
/// Messages sent in response to [`StreamRequest`].
///
/// Empty list of responses means the end of the stream.
#[derive(Debug, Encode, Decode)]
pub enum GenericStreamResponses<Response> {
/// Some responses, but the stream didn't end yet
Continue {
/// Monotonically increasing index of responses in a stream
index: u32,
/// Individual responses
responses: VecDeque<Response>,
/// Subject where to send acknowledgement of received stream response indices, which acts as
/// a backpressure mechanism
ack_subject: String,
},
/// Remaining responses and this is the end of the stream.
Last {
/// Monotonically increasing index of responses in a stream
index: u32,
/// Individual responses
responses: VecDeque<Response>,
},
}
impl<Response> From<GenericStreamResponses<Response>> for VecDeque<Response> {
#[inline]
fn from(value: GenericStreamResponses<Response>) -> Self {
match value {
GenericStreamResponses::Continue { responses, .. } => responses,
GenericStreamResponses::Last { responses, .. } => responses,
}
}
}
impl<Response> GenericStreamResponses<Response> {
fn next(&mut self) -> Option<Response> {
match self {
GenericStreamResponses::Continue { responses, .. } => responses.pop_front(),
GenericStreamResponses::Last { responses, .. } => responses.pop_front(),
}
}
fn index(&self) -> u32 {
match self {
GenericStreamResponses::Continue { index, .. } => *index,
GenericStreamResponses::Last { index, .. } => *index,
}
}
fn ack_subject(&self) -> Option<&str> {
if let GenericStreamResponses::Continue { ack_subject, .. } = self {
Some(ack_subject)
} else {
None
}
}
fn is_last(&self) -> bool {
matches!(self, Self::Last { .. })
}
}
/// Generic stream request that expects a stream of responses.
///
/// Internally it is expected that [`GenericStreamResponses<Request::Response>`] messages will be
/// sent to auto-generated subject specified in `response_subject` field.
#[derive(Debug, Encode, Decode)]
#[non_exhaustive]
pub struct StreamRequest<Request>
where
Request: GenericStreamRequest,
{
/// Request
pub request: Request,
/// Topic to send a stream of [`GenericStreamResponses<Request::Response>`]s to
pub response_subject: String,
}
impl<Request> StreamRequest<Request>
where
Request: GenericStreamRequest,
{
/// Create new stream request
pub fn new(request: Request) -> Self {
Self {
request,
response_subject: format!("stream-response.{}", Ulid::new()),
}
}
}
/// Stream request error
#[derive(Debug, Error)]
pub enum StreamRequestError {
/// Subscribe error
#[error("Subscribe error: {0}")]
Subscribe(#[from] SubscribeError),
/// Publish error
#[error("Publish error: {0}")]
Publish(#[from] PublishError),
}
/// Wrapper around subscription that transforms [`GenericStreamResponses<Response>`] messages into a
/// normal `Response` stream.
#[derive(Debug, Deref, DerefMut)]
#[pin_project::pin_project]
pub struct StreamResponseSubscriber<Response> {
#[pin]
#[deref]
#[deref_mut]
subscriber: Subscriber,
response_subject: String,
buffered_responses: Option<GenericStreamResponses<Response>>,
next_index: u32,
acknowledgement_sender: mpsc::UnboundedSender<(String, u32)>,
_background_task: AsyncJoinOnDrop<()>,
_phantom: PhantomData<Response>,
}
impl<Response> Stream for StreamResponseSubscriber<Response>
where
Response: Decode,
{
type Item = Response;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
if let Some(buffered_responses) = self.buffered_responses.as_mut() {
if let Some(response) = buffered_responses.next() {
return Poll::Ready(Some(response));
} else if buffered_responses.is_last() {
return Poll::Ready(None);
}
self.buffered_responses.take();
self.next_index += 1;
}
let mut projected = self.project();
match projected.subscriber.poll_next_unpin(cx) {
Poll::Ready(Some(message)) => {
match GenericStreamResponses::<Response>::decode(&mut message.payload.as_ref()) {
Ok(mut responses) => {
if responses.index() != *projected.next_index {
warn!(
actual_index = %responses.index(),
expected_index = %*projected.next_index,
message_type = %type_name::<Response>(),
response_subject = %projected.response_subject,
"Received unexpected response stream index, aborting stream"
);
return Poll::Ready(None);
}
if let Some(ack_subject) = responses.ack_subject() {
let index = responses.index();
let ack_subject = ack_subject.to_string();
if let Err(error) = projected
.acknowledgement_sender
.unbounded_send((ack_subject.clone(), index))
{
warn!(
%error,
%index,
message_type = %type_name::<Response>(),
response_subject = %projected.response_subject,
%ack_subject,
"Failed to send acknowledgement for stream response"
);
}
}
if let Some(response) = responses.next() {
*projected.buffered_responses = Some(responses);
Poll::Ready(Some(response))
} else {
Poll::Ready(None)
}
}
Err(error) => {
warn!(
%error,
response_type = %type_name::<Response>(),
response_subject = %projected.response_subject,
message = %hex::encode(message.payload),
"Failed to decode stream response"
);
Poll::Ready(None)
}
}
}
Poll::Ready(None) => Poll::Ready(None),
Poll::Pending => Poll::Pending,
}
}
}
impl<Response> StreamResponseSubscriber<Response> {
fn new(subscriber: Subscriber, response_subject: String, nats_client: NatsClient) -> Self {
let (acknowledgement_sender, mut acknowledgement_receiver) =
mpsc::unbounded::<(String, u32)>();
let ack_publisher_fut = {
let response_subject = response_subject.clone();
async move {
while let Some((subject, index)) = acknowledgement_receiver.next().await {
trace!(
%subject,
%index,
%response_subject,
%index,
"Sending stream response acknowledgement"
);
if let Err(error) = nats_client
.publish(subject.clone(), index.to_le_bytes().to_vec().into())
.await
{
warn!(
%error,
%subject,
%index,
%response_subject,
%index,
"Failed to send stream response acknowledgement"
);
return;
}
}
}
};
let background_task =
AsyncJoinOnDrop::new(tokio::spawn(ack_publisher_fut.in_current_span()), true);
Self {
response_subject,
subscriber,
buffered_responses: None,
next_index: 0,
acknowledgement_sender,
_background_task: background_task,
_phantom: PhantomData,
}
}
}
/// Generic one-off notification
pub trait GenericNotification: Encode + Decode + fmt::Debug + Send + Sync + 'static {
/// Notification subject with optional `*` in place of application instance receiving the
/// request
const SUBJECT: &'static str;
}
/// Generic broadcast message.
///
/// Broadcast messages are sent by an instance to (potentially) an instance-specific subject that
/// any other app can subscribe to. The same broadcast message can also originate from multiple
/// places and be de-duplicated using [`Self::deterministic_message_id`].
pub trait GenericBroadcast: Encode + Decode + fmt::Debug + Send + Sync + 'static {
/// Broadcast subject with optional `*` in place of application instance sending broadcast
const SUBJECT: &'static str;
/// Deterministic message ID that is used for de-duplicating messages broadcast by different
/// instances
fn deterministic_message_id(&self) -> Option<HeaderValue> {
None
}
}
/// Subscriber wrapper that decodes messages automatically and skips messages that can't be decoded
#[derive(Debug, Deref, DerefMut)]
#[pin_project::pin_project]
pub struct SubscriberWrapper<Message> {
#[pin]
#[deref]
#[deref_mut]
subscriber: Subscriber,
_phantom: PhantomData<Message>,
}
impl<Message> Stream for SubscriberWrapper<Message>
where
Message: Decode,
{
type Item = Message;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
match self.project().subscriber.poll_next_unpin(cx) {
Poll::Ready(Some(message)) => match Message::decode(&mut message.payload.as_ref()) {
Ok(message) => Poll::Ready(Some(message)),
Err(error) => {
warn!(
%error,
message_type = %type_name::<Message>(),
message = %hex::encode(message.payload),
"Failed to decode stream message"
);
Poll::Pending
}
},
Poll::Ready(None) => Poll::Ready(None),
Poll::Pending => Poll::Pending,
}
}
}
#[derive(Debug)]
struct Inner {
client: Client,
request_retry_backoff_policy: ExponentialBackoff,
approximate_max_message_size: usize,
max_message_size: usize,
}
/// NATS client wrapper that can be used to interact with other Subspace-specific clients
#[derive(Debug, Clone)]
pub struct NatsClient {
inner: Arc<Inner>,
}
impl Deref for NatsClient {
type Target = Client;
#[inline]
fn deref(&self) -> &Self::Target {
&self.inner.client
}
}
impl NatsClient {
/// Create new instance by connecting to specified addresses
pub async fn new<A: ToServerAddrs>(
addrs: A,
request_retry_backoff_policy: ExponentialBackoff,
) -> Result<Self, async_nats::Error> {
let servers = addrs.to_server_addrs()?.collect::<Vec<_>>();
Self::from_client(
async_nats::connect_with_options(
&servers,
ConnectOptions::default().request_timeout(Some(REQUEST_TIMEOUT)),
)
.await?,
request_retry_backoff_policy,
)
}
/// Create new client from existing NATS instance
pub fn from_client(
client: Client,
request_retry_backoff_policy: ExponentialBackoff,
) -> Result<Self, async_nats::Error> {
let max_payload = client.server_info().max_payload;
if max_payload < EXPECTED_MESSAGE_SIZE {
return Err(format!(
"Max payload {max_payload} is smaller than expected {EXPECTED_MESSAGE_SIZE}, \
increase it by specifying max_payload = 2MB or higher number in NATS configuration"
)
.into());
}
let inner = Inner {
client,
request_retry_backoff_policy,
// Allow up to 90%, the rest will be wrapper data structures, etc.
approximate_max_message_size: max_payload * 9 / 10,
// Allow up to 90%, the rest will be wrapper data structures, etc.
max_message_size: max_payload,
};
Ok(Self {
inner: Arc::new(inner),
})
}
/// Approximate max message size (a few more bytes will not hurt), the actual limit is expected
/// to be a bit higher
pub fn approximate_max_message_size(&self) -> usize {
self.inner.approximate_max_message_size
}
/// Make request and wait for response
pub async fn request<Request>(
&self,
request: &Request,
instance: Option<&str>,
) -> Result<Request::Response, RequestError>
where
Request: GenericRequest,
{
let subject = subject_with_instance(Request::SUBJECT, instance);
let mut maybe_retry_backoff = None;
let message = loop {
match self
.inner
.client
.request(subject.clone(), request.encode().into())
.await
{
Ok(message) => {
break message;
}
Err(error) => {
match error.kind() {
RequestErrorKind::TimedOut | RequestErrorKind::NoResponders => {
// Continue with retries
}
RequestErrorKind::Other => {
return Err(error);
}
}
let retry_backoff = maybe_retry_backoff.get_or_insert_with(|| {
let mut retry_backoff = self.inner.request_retry_backoff_policy.clone();
retry_backoff.reset();
retry_backoff
});
if let Some(delay) = retry_backoff.next_backoff() {
debug!(
%subject,
%error,
request_type = %type_name::<Request>(),
?delay,
"Failed to make request, retrying after some delay"
);
tokio::time::sleep(delay).await;
continue;
} else {
return Err(error);
}
}
}
};
let response =
Request::Response::decode(&mut message.payload.as_ref()).map_err(|error| {
warn!(
%subject,
%error,
response_type = %type_name::<Request::Response>(),
response = %hex::encode(message.payload),
"Response decoding failed"
);
RequestErrorKind::Other
})?;
Ok(response)
}
/// Responds to requests from the given subject using the provided processing function.
///
/// This will create a subscription on the subject for the given instance (if provided) and
/// queue group. Incoming messages will be deserialized as the request type `Request` and passed
/// to the `process` function to produce a response of type `Request::Response`. The response
/// will then be sent back on the reply subject from the original request.
///
/// Each request is processed in a newly created async tokio task.
///
/// # Arguments
///
/// * `instance` - Optional instance name to use in place of the `*` in the subject
/// * `group` - The queue group name for the subscription
/// * `process` - The function to call with the decoded request to produce a response
pub async fn request_responder<Request, F, OP>(
&self,
instance: Option<&str>,
queue_group: Option<String>,
process: OP,
) -> anyhow::Result<()>
where
Request: GenericRequest,
F: Future<Output = Option<Request::Response>> + Send,
OP: Fn(Request) -> F + Send + Sync,
{
// Initialize with pending future so it never ends
let mut processing = FuturesUnordered::from_iter([
Box::pin(pending()) as Pin<Box<dyn Future<Output = ()> + Send>>
]);
let subject = subject_with_instance(Request::SUBJECT, instance);
let subscription = if let Some(queue_group) = queue_group {
self.inner
.client
.queue_subscribe(subject, queue_group)
.await
} else {
self.inner.client.subscribe(subject).await
}
.map_err(|error| {
anyhow!(
"Failed to subscribe to {} requests for {instance:?}: {error}",
type_name::<Request>(),
)
})?;
debug!(
request_type = %type_name::<Request>(),
?subscription,
"Requests subscription"
);
let mut subscription = subscription.fuse();
loop {
select! {
maybe_message = subscription.next() => {
let Some(message) = maybe_message else {
break;
};
// Create background task for concurrent processing
processing.push(Box::pin(self.process_request(
message,
&process,
)));
}
_ = processing.next() => {
// Nothing to do here
}
}
}
Ok(())
}
async fn process_request<Request, F, OP>(&self, message: Message, process: OP)
where
Request: GenericRequest,
F: Future<Output = Option<Request::Response>> + Send,
OP: Fn(Request) -> F + Send + Sync,
{
let Some(reply_subject) = message.reply else {
return;
};
let message_payload_size = message.payload.len();
let request = match Request::decode(&mut message.payload.as_ref()) {
Ok(request) => {
// Free allocation early
drop(message.payload);
request
}
Err(error) => {
warn!(
request_type = %type_name::<Request>(),
%error,
message = %hex::encode(message.payload),
"Failed to decode request"
);
return;
}
};
// Avoid printing large messages in logs
if message_payload_size > 1024 {
trace!(
request_type = %type_name::<Request>(),
%reply_subject,
"Processing request"
);
} else {
trace!(
request_type = %type_name::<Request>(),
?request,
%reply_subject,
"Processing request"
);
}
if let Some(response) = process(request).await
&& let Err(error) = self.publish(reply_subject, response.encode().into()).await
{
warn!(
request_type = %type_name::<Request>(),
%error,
"Failed to send response"
);
}
}
/// Make request that expects stream response
pub async fn stream_request<Request>(
&self,
request: Request,
instance: Option<&str>,
) -> Result<StreamResponseSubscriber<Request::Response>, StreamRequestError>
where
Request: GenericStreamRequest,
{
let stream_request = StreamRequest::new(request);
let subscriber = self
.inner
.client
.subscribe(stream_request.response_subject.clone())
.await?;
let stream_request_subject = subject_with_instance(Request::SUBJECT, instance);
debug!(
request_type = %type_name::<Request>(),
%stream_request_subject,
?subscriber,
"Stream request subscription"
);
self.inner
.client
.publish(stream_request_subject, stream_request.encode().into())
.await?;
Ok(StreamResponseSubscriber::new(
subscriber,
stream_request.response_subject,
self.clone(),
))
}
/// Helper method to send responses to requests initiated with [`Self::stream_request`]
pub async fn stream_response<Request, S>(&self, response_subject: String, response_stream: S)
where
Request: GenericStreamRequest,
S: Stream<Item = Request::Response> + Unpin,
{
type Response<Request> =
GenericStreamResponses<<Request as GenericStreamRequest>::Response>;
let mut response_stream = response_stream.fuse();
// Pull the first element to measure response size
let first_element = match response_stream.next().await {
Some(first_element) => first_element,
None => {
if let Err(error) = self
.publish(
response_subject.clone(),
Response::<Request>::Last {
index: 0,
responses: VecDeque::new(),
}
.encode()
.into(),
)
.await
{
warn!(
%response_subject,
%error,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
"Failed to send stream response"
);
}
return;
}
};
let max_message_size = self.inner.max_message_size;
let max_responses_per_message =
self.approximate_max_message_size() / first_element.encoded_size();
let ack_subject = format!("stream-response-ack.{}", Ulid::new());
let mut ack_subscription = match self.subscribe(ack_subject.clone()).await {
Ok(ack_subscription) => ack_subscription,
Err(error) => {
warn!(
%response_subject,
%error,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
"Failed to subscribe to ack subject"
);
return;
}
};
debug!(
%response_subject,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
?ack_subscription,
"Ack subscription subscription"
);
let mut index = 0;
// Initialize buffer that will be reused for responses
let mut buffer = VecDeque::with_capacity(max_responses_per_message);
buffer.push_back(first_element);
let mut overflow_buffer = VecDeque::new();
loop {
// Try to fill the buffer
let mut local_response_stream = response_stream
.by_ref()
.take(max_responses_per_message - buffer.len());
if buffer.is_empty() {
if let Some(element) = local_response_stream.next().await {
buffer.push_back(element);
}
}
while let Some(element) = local_response_stream.next().now_or_never().flatten() {
buffer.push_back(element);
}
loop {
let is_done = response_stream.is_done() && overflow_buffer.is_empty();
let num_messages = buffer.len();
let response = if is_done {
Response::<Request>::Last {
index,
responses: buffer,
}
} else {
Response::<Request>::Continue {
index,
responses: buffer,
ack_subject: ack_subject.clone(),
}
};
let encoded_response = response.encode();
let encoded_response_len = encoded_response.len();
// When encoded response is too large, remove one of the responses from it and try
// again
if encoded_response_len > max_message_size {
buffer = response.into();
if let Some(element) = buffer.pop_back() {
if buffer.is_empty() {
error!(
?element,
encoded_response_len,
max_message_size,
"Element was too large to fit into NATS message, this is an \
implementation bug"
);
}
overflow_buffer.push_front(element);
continue;
} else {
error!(
%response_subject,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
"Empty response overflown message size, this should never happen"
);
return;
}
}
debug!(
%response_subject,
num_messages,
%index,
%is_done,
"Publishing stream response messages",
);
if let Err(error) = self
.publish(response_subject.clone(), encoded_response.into())
.await
{
warn!(
%response_subject,
%error,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
"Failed to send stream response"
);
return;
}
if is_done {
return;
} else {
buffer = response.into();
buffer.clear();
// Fill buffer with any overflown responses that may have been stored
buffer.extend(overflow_buffer.drain(..));
}
if index >= 1 {
// Acknowledgements are received with delay
let expected_index = index - 1;
trace!(
%response_subject,
%expected_index,
"Waiting for acknowledgement"
);
match tokio::time::timeout(ACKNOWLEDGEMENT_TIMEOUT, ack_subscription.next())
.await
{
Ok(Some(message)) => {
if let Some(received_index) = message
.payload
.split_at_checked(mem::size_of::<u32>())
.map(|(bytes, _)| {
u32::from_le_bytes(
bytes.try_into().expect("Correctly chunked slice; qed"),
)
})
{
debug!(
%response_subject,
%received_index,
"Received acknowledgement"
);
if received_index != expected_index {
warn!(
%response_subject,
%received_index,
%expected_index,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
message = %hex::encode(message.payload),
"Unexpected acknowledgement index"
);
return;
}
} else {
warn!(
%response_subject,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
message = %hex::encode(message.payload),
"Unexpected acknowledgement message"
);
return;
}
}
Ok(None) => {
warn!(
%response_subject,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
"Acknowledgement stream ended unexpectedly"
);
return;
}
Err(_error) => {
warn!(
%response_subject,
%expected_index,
request_type = %type_name::<Request>(),
response_type = %type_name::<Request::Response>(),
"Acknowledgement wait timed out"
);
return;
}
}
}
index += 1;
// Unless `overflow_buffer` wasn't empty abort inner loop
if buffer.is_empty() {
break;
}
}
}
}
/// Make notification without waiting for response
pub async fn notification<Notification>(
&self,
notification: &Notification,
instance: Option<&str>,
) -> Result<(), PublishError>
where
Notification: GenericNotification,
{
self.inner
.client
.publish(
subject_with_instance(Notification::SUBJECT, instance),
notification.encode().into(),
)
.await
}
/// Send a broadcast message
pub async fn broadcast<Broadcast>(
&self,
message: &Broadcast,
instance: &str,
) -> Result<(), PublishError>
where
Broadcast: GenericBroadcast,
{
self.inner
.client
.publish_with_headers(
Broadcast::SUBJECT.replace('*', instance),
{
let mut headers = HeaderMap::new();
if let Some(message_id) = message.deterministic_message_id() {
headers.insert("Nats-Msg-Id", message_id);
}
headers
},
message.encode().into(),
)
.await
}
/// Simple subscription that will produce decoded stream requests, while skipping messages that
/// fail to decode
pub async fn subscribe_to_stream_requests<Request>(
&self,
instance: Option<&str>,
queue_group: Option<String>,
) -> Result<SubscriberWrapper<StreamRequest<Request>>, SubscribeError>
where
Request: GenericStreamRequest,
{
self.simple_subscribe(Request::SUBJECT, instance, queue_group)
.await
}
/// Simple subscription that will produce decoded notifications, while skipping messages that
/// fail to decode
pub async fn subscribe_to_notifications<Notification>(
&self,
instance: Option<&str>,
queue_group: Option<String>,
) -> Result<SubscriberWrapper<Notification>, SubscribeError>
where
Notification: GenericNotification,
{
self.simple_subscribe(Notification::SUBJECT, instance, queue_group)
.await
}
/// Simple subscription that will produce decoded broadcasts, while skipping messages that
/// fail to decode
pub async fn subscribe_to_broadcasts<Broadcast>(
&self,
instance: Option<&str>,
queue_group: Option<String>,
) -> Result<SubscriberWrapper<Broadcast>, SubscribeError>
where
Broadcast: GenericBroadcast,
{
self.simple_subscribe(Broadcast::SUBJECT, instance, queue_group)
.await
}
/// Simple subscription that will produce decoded messages, while skipping messages that fail to
/// decode
async fn simple_subscribe<Message>(
&self,
subject: &'static str,
instance: Option<&str>,
queue_group: Option<String>,
) -> Result<SubscriberWrapper<Message>, SubscribeError>
where
Message: Decode,
{
let subscriber = if let Some(queue_group) = queue_group {
self.inner
.client
.queue_subscribe(subject_with_instance(subject, instance), queue_group)
.await?
} else {
self.inner
.client
.subscribe(subject_with_instance(subject, instance))
.await?
};
debug!(
%subject,
message_type = %type_name::<Message>(),
?subscriber,
"Simple subscription"
);
Ok(SubscriberWrapper {
subscriber,
_phantom: PhantomData,
})
}
}
fn subject_with_instance(subject: &'static str, instance: Option<&str>) -> Subject {
if let Some(instance) = instance {
Subject::from(subject.replace('*', instance))
} else {
Subject::from_static(subject)
}
}