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iopub.rs
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iopub.rs
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/*
* iopub.rs
*
* Copyright (C) 2022 Posit Software, PBC. All rights reserved.
*
*/
use std::time::Duration;
use crossbeam::channel::tick;
use crossbeam::channel::Receiver;
use crossbeam::channel::Sender;
use crossbeam::select;
use log::trace;
use log::warn;
use crate::error::Error;
use crate::socket::socket::Socket;
use crate::wire::comm_close::CommClose;
use crate::wire::comm_msg::CommWireMsg;
use crate::wire::comm_open::CommOpen;
use crate::wire::display_data::DisplayData;
use crate::wire::execute_error::ExecuteError;
use crate::wire::execute_input::ExecuteInput;
use crate::wire::execute_result::ExecuteResult;
use crate::wire::header::JupyterHeader;
use crate::wire::jupyter_message::JupyterMessage;
use crate::wire::jupyter_message::ProtocolMessage;
use crate::wire::status::ExecutionState;
use crate::wire::status::KernelStatus;
use crate::wire::stream::Stream;
use crate::wire::stream::StreamOutput;
use crate::wire::update_display_data::UpdateDisplayData;
pub struct IOPub {
/// The underlying IOPub socket
socket: Socket,
/// A channel that receives IOPub messages from other threads
receiver: Receiver<IOPubMessage>,
/// The current message context; attached to outgoing messages to pair
/// outputs with the message that caused them.
shell_context: Option<JupyterHeader>,
control_context: Option<JupyterHeader>,
/// A buffer for the active stdout/stderr stream to batch stream messages
/// that we send to the frontend, since this can be extremely high traffic.
/// We only have 1 buffer because we immediately flush the active stream if
/// we are about to process a message for the other stream. The idea is that
/// this avoids a message sequence of <stdout, stderr, stdout> getting
/// accidentally sent to the frontend as <stdout, stdout, stderr>.
buffer: StreamBuffer,
}
/// Enumeration of possible channels that an IOPub message can be associated
/// with.
pub enum IOPubContextChannel {
Shell,
Control,
}
/// Enumeration of all messages that can be delivered from the IOPub PUB/SUB
/// socket. These messages generally are created on other threads and then sent
/// via a channel to the IOPub thread.
pub enum IOPubMessage {
Status(JupyterHeader, IOPubContextChannel, KernelStatus),
ExecuteResult(ExecuteResult),
ExecuteError(ExecuteError),
ExecuteInput(ExecuteInput),
Stream(StreamOutput),
CommOpen(CommOpen),
CommMsgReply(JupyterHeader, CommWireMsg),
CommMsgEvent(CommWireMsg),
CommClose(String),
DisplayData(DisplayData),
UpdateDisplayData(UpdateDisplayData),
Wait(Wait),
}
/// A special IOPub message used to block the sender until the IOPub queue has
/// forwarded all messages before this one on to the frontend.
pub struct Wait {
pub wait_tx: Sender<()>,
}
impl IOPub {
/// Create a new IOPub socket wrapper.
///
/// * `socket` - The ZeroMQ socket that will deliver IOPub messages to
/// subscribed clients.
/// * `receiver` - The receiver channel that will receive IOPub
/// messages from other threads.
pub fn new(socket: Socket, receiver: Receiver<IOPubMessage>) -> Self {
let buffer = StreamBuffer::new(Stream::Stdout);
Self {
socket,
receiver,
shell_context: None,
control_context: None,
buffer,
}
}
/// Listen for IOPub messages from other threads. Does not return.
pub fn listen(&mut self) {
// Begin by emitting the starting state
self.emit_state(ExecutionState::Starting);
// Flush the active stream (either stdout or stderr) at regular
// intervals
let flush_interval = *StreamBuffer::interval();
let flush_interval = tick(flush_interval);
loop {
select! {
recv(self.receiver) -> message => {
match message {
Ok(message) => {
if let Err(error) = self.process_message(message) {
warn!("Error delivering iopub message: {error:?}")
}
},
Err(error) => {
warn!("Failed to receive iopub message: {error:?}");
},
}
},
recv(flush_interval) -> message => {
match message {
Ok(_) => self.flush_stream(),
Err(_) => unreachable!()
}
}
}
}
}
/// Process an IOPub message from another thread.
fn process_message(&mut self, message: IOPubMessage) -> Result<(), Error> {
match message {
IOPubMessage::Status(context, context_channel, msg) => {
// When we enter the Busy state as a result of a message, we
// update the context. Future messages to IOPub name this
// context in the parent header sent to the client; this makes
// it possible for the client to associate events/output with
// their originator without requiring us to thread the values
// through the stack.
match (&context_channel, &msg.execution_state) {
(IOPubContextChannel::Control, ExecutionState::Busy) => {
self.control_context = Some(context.clone());
},
(IOPubContextChannel::Control, ExecutionState::Idle) => {
self.flush_stream();
self.control_context = None;
},
(IOPubContextChannel::Control, ExecutionState::Starting) => {
// Nothing to do
},
(IOPubContextChannel::Shell, ExecutionState::Busy) => {
self.shell_context = Some(context.clone());
},
(IOPubContextChannel::Shell, ExecutionState::Idle) => {
self.flush_stream();
self.shell_context = None;
},
(IOPubContextChannel::Shell, ExecutionState::Starting) => {
// Nothing to do
},
}
self.send_message_with_header(context, msg)
},
IOPubMessage::ExecuteResult(msg) => {
self.flush_stream();
self.send_message_with_context(msg, IOPubContextChannel::Shell)
},
IOPubMessage::ExecuteError(msg) => {
self.flush_stream();
self.send_message_with_context(msg, IOPubContextChannel::Shell)
},
IOPubMessage::ExecuteInput(msg) => {
self.send_message_with_context(msg, IOPubContextChannel::Shell)
},
IOPubMessage::Stream(msg) => self.process_stream_message(msg),
IOPubMessage::CommOpen(msg) => self.send_message(msg),
IOPubMessage::CommMsgEvent(msg) => self.send_message(msg),
IOPubMessage::CommMsgReply(header, msg) => self.send_message_with_header(header, msg),
IOPubMessage::CommClose(comm_id) => self.send_message(CommClose { comm_id }),
IOPubMessage::DisplayData(msg) => {
self.flush_stream();
self.send_message_with_context(msg, IOPubContextChannel::Shell)
},
IOPubMessage::UpdateDisplayData(msg) => {
self.flush_stream();
self.send_message_with_context(msg, IOPubContextChannel::Shell)
},
IOPubMessage::Wait(msg) => self.process_wait_request(msg),
}
}
/// Send a message using the underlying socket with the given content.
/// No parent is assumed.
fn send_message<T: ProtocolMessage>(&self, content: T) -> Result<(), Error> {
self.send_message_impl(None, content)
}
/// Send a message using the underlying socket with the given content. The
/// parent message is assumed to be the current context.
fn send_message_with_context<T: ProtocolMessage>(
&self,
content: T,
context_channel: IOPubContextChannel,
) -> Result<(), Error> {
let context = match context_channel {
IOPubContextChannel::Control => &self.control_context,
IOPubContextChannel::Shell => &self.shell_context,
};
self.send_message_impl(context.clone(), content)
}
/// Send a message using the underlying socket with the given content and
/// specific header. Used when the parent message is known by the message
/// sender, typically in comm message replies.
fn send_message_with_header<T: ProtocolMessage>(
&self,
header: JupyterHeader,
content: T,
) -> Result<(), Error> {
self.send_message_impl(Some(header), content)
}
fn send_message_impl<T: ProtocolMessage>(
&self,
header: Option<JupyterHeader>,
content: T,
) -> Result<(), Error> {
let msg = JupyterMessage::<T>::create(content, header, &self.socket.session);
msg.send(&self.socket)
}
/// Flushes the active stream, sending along the message if the buffer
/// wasn't empty. Handles its own errors since we often call this before
/// sending some other message and we don't want to prevent that from going
/// through.
fn flush_stream(&mut self) {
if self.buffer.is_empty() {
return;
}
let message = self.buffer.drain();
let Err(error) = self.send_message_with_context(message, IOPubContextChannel::Shell) else {
// Message sent successfully
return;
};
let name = match self.buffer.name {
Stream::Stdout => "stdout",
Stream::Stderr => "stderr",
};
warn!("Error delivering iopub 'stream' message over '{name}': {error:?}");
}
/// Processes a `Stream` message by appending it to the stream buffer
///
/// The buffer will be flushed on the next tick interval unless it is
/// manually flushed before then.
///
/// If this new message switches streams, then we flush the existing stream
/// before switching.
fn process_stream_message(&mut self, message: StreamOutput) -> Result<(), Error> {
if message.name != self.buffer.name {
// Swap streams, but flush the existing stream first
self.flush_stream();
self.buffer = StreamBuffer::new(message.name);
}
self.buffer.push(message.text);
Ok(())
}
/// Process a `Wait` request
///
/// Processing the request is simple, we just respond. The actual "wait"
/// occurred in `iopub_tx` / `iopub_rx` where all other pending messages had
/// to be send along before we got here.
///
/// Note that this doesn't guarantee that the frontend has received all of
/// the messages on the IOPub socket in front of this one. So even after
/// waiting for the queue to empty, it is possible for a message on a
/// different socket that is sent after waiting to still get processed by
/// the frontend before the messages we cleared from the IOPub queue.
fn process_wait_request(&mut self, message: Wait) -> Result<(), Error> {
message.wait_tx.send(()).unwrap();
Ok(())
}
/// Emits the given kernel state to the client.
fn emit_state(&self, state: ExecutionState) {
trace!("Entering kernel state: {:?}", state);
if let Err(err) = JupyterMessage::<KernelStatus>::create(
KernelStatus {
execution_state: state,
},
None,
&self.socket.session,
)
.send(&self.socket)
{
warn!("Could not emit kernel's state. {}", err)
}
}
}
struct StreamBuffer {
name: Stream,
buffer: Vec<String>,
}
impl StreamBuffer {
fn new(name: Stream) -> Self {
return StreamBuffer {
name,
buffer: Vec::new(),
};
}
fn push(&mut self, message: String) {
self.buffer.push(message);
}
fn is_empty(&self) -> bool {
self.buffer.is_empty()
}
fn drain(&mut self) -> StreamOutput {
let text = self.buffer.join("");
self.buffer.clear();
StreamOutput {
name: self.name,
text,
}
}
fn interval() -> &'static Duration {
static STREAM_BUFFER_INTERVAL: Duration = Duration::from_millis(80);
&STREAM_BUFFER_INTERVAL
}
}