codex/codex-rs/exec-server/src/rpc_server_requests.rs

use std::collections::HashMap;
use std::sync::Arc;
use std::sync::Mutex;
use std::sync::atomic::AtomicI64;
use std::sync::atomic::Ordering;
use std::time::Duration;

use codex_exec_server_protocol::JSONRPCRequest;
use codex_exec_server_protocol::RequestId;
use serde::Serialize;
use serde::de::DeserializeOwned;
use serde_json::Value;
use tokio::sync::Semaphore;
use tokio::sync::mpsc;
use tokio::sync::oneshot;
use tokio::time::timeout;
use tokio_util::sync::CancellationToken;

use crate::rpc::RpcCallError;
use crate::rpc::RpcServerOutboundMessage;

pub(crate) const MAX_IN_FLIGHT_SERVER_CALLS: usize = 256;

type PendingRequest = oneshot::Sender<Result<Value, RpcCallError>>;

#[derive(Clone)]
pub(crate) struct RpcServerRequestSender {
    inner: Arc<RpcServerRequestSenderInner>,
}

struct RpcServerRequestSenderInner {
    outgoing_tx: mpsc::Sender<RpcServerOutboundMessage>,
    pending: Mutex<HashMap<RequestId, PendingRequest>>,
    call_slots: Semaphore,
    next_request_id: AtomicI64,
    closed: CancellationToken,
}

struct PendingServerRequestGuard {
    inner: Arc<RpcServerRequestSenderInner>,
    request_id: RequestId,
}

impl Drop for PendingServerRequestGuard {
    fn drop(&mut self) {
        self.inner
            .pending
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .remove(&self.request_id);
    }
}

impl RpcServerRequestSender {
    pub(crate) fn new(outgoing_tx: mpsc::Sender<RpcServerOutboundMessage>) -> Self {
        Self {
            inner: Arc::new(RpcServerRequestSenderInner {
                outgoing_tx,
                pending: Mutex::new(HashMap::new()),
                call_slots: Semaphore::new(MAX_IN_FLIGHT_SERVER_CALLS),
                next_request_id: AtomicI64::new(1),
                closed: CancellationToken::new(),
            }),
        }
    }

    pub(crate) async fn call_with_timeout<P, T>(
        &self,
        method: &str,
        params: &P,
        call_timeout: Duration,
    ) -> Result<T, RpcCallError>
    where
        P: Serialize,
        T: DeserializeOwned,
    {
        let _call_slot = self.inner.call_slots.try_acquire().map_err(|_| {
            RpcCallError::PendingRequestLimitExceeded {
                limit: MAX_IN_FLIGHT_SERVER_CALLS,
            }
        })?;
        let params = serde_json::to_value(params).map_err(RpcCallError::Json)?;
        let request_id =
            RequestId::Integer(self.inner.next_request_id.fetch_add(1, Ordering::SeqCst));
        let (response_tx, response_rx) = oneshot::channel();
        {
            let mut pending = self
                .inner
                .pending
                .lock()
                .unwrap_or_else(std::sync::PoisonError::into_inner);
            if self.inner.closed.is_cancelled() {
                return Err(RpcCallError::Closed);
            }
            pending.insert(request_id.clone(), response_tx);
        }
        let _pending = PendingServerRequestGuard {
            inner: Arc::clone(&self.inner),
            request_id: request_id.clone(),
        };
        let request = RpcServerOutboundMessage::Request(JSONRPCRequest {
            id: request_id,
            method: method.to_string(),
            params: Some(params),
            trace: codex_otel::current_span_w3c_trace_context(),
        });

        let response = timeout(call_timeout, async {
            tokio::select! {
                biased;
                _ = self.inner.closed.cancelled() => return Err(RpcCallError::Closed),
                result = self.inner.outgoing_tx.send(request) => {
                    result.map_err(|_| RpcCallError::Closed)?;
                }
            }
            response_rx.await.map_err(|_| RpcCallError::Closed)?
        })
        .await
        .map_err(|_| RpcCallError::TimedOut {
            method: method.to_string(),
            timeout: call_timeout,
        })??;
        serde_json::from_value(response).map_err(RpcCallError::Json)
    }

    pub(crate) fn complete(
        &self,
        request_id: RequestId,
        result: Result<Value, RpcCallError>,
    ) -> bool {
        if let Some(pending) = self
            .inner
            .pending
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .remove(&request_id)
        {
            let _ = pending.send(result);
            true
        } else {
            matches!(
                request_id,
                RequestId::Integer(id)
                    if id > 0 && id < self.inner.next_request_id.load(Ordering::Acquire)
            )
        }
    }

    pub(crate) fn close(&self) {
        self.inner.closed.cancel();
        let pending = {
            let mut pending = self
                .inner
                .pending
                .lock()
                .unwrap_or_else(std::sync::PoisonError::into_inner);
            pending
                .drain()
                .map(|(_, pending)| pending)
                .collect::<Vec<_>>()
        };
        for pending in pending {
            let _ = pending.send(Err(RpcCallError::Closed));
        }
    }
}

#[cfg(test)]
#[path = "rpc_server_requests_tests.rs"]
mod tests;