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fix: record match results synchronously to eliminate race condition (#13) #14

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fix: record match results synchronously to eliminate race condition (#13) #14

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49 changes: 33 additions & 16 deletions pact_mock_server/src/hyper_server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ use std::collections::HashMap;
use std::fmt;
use std::fmt::{Display, Formatter};
use std::net::SocketAddr;
#[cfg(feature = "tls")] use std::sync::Arc;
use std::sync::{Arc, Mutex};
use std::time::Duration;

#[allow(unused_imports)] use anyhow::anyhow;
Expand Down Expand Up @@ -72,7 +72,8 @@ pub(crate) async fn create_and_bind(
server_id: String,
pact: V4Pact,
addr: SocketAddr,
config: MockServerConfig
config: MockServerConfig,
matches: Arc<Mutex<Vec<MatchResult>>>
) -> anyhow::Result<(SocketAddr, oneshot::Sender<()>, mpsc::Receiver<MockServerEvent>, JoinHandle<()>)> {
let listener = TcpListener::bind(addr).await?;
let local_addr = listener.local_addr()?;
Expand All @@ -88,6 +89,7 @@ pub(crate) async fn create_and_bind(
let server_id = server_id.clone();
let pact = pact.clone();
let config = config.clone();
let matches = matches.clone();

select! {
connection = listener.accept() => {
Expand All @@ -106,9 +108,10 @@ pub(crate) async fn create_and_bind(
let event_send = ev.clone();
let config = config.clone();
let server_id = sid.clone();
let matches = matches.clone();
LOG_ID.scope(server_id, async move {
handle_mock_request_error(
handle_request(req, pact.clone(), event_send.clone(), &local_addr, &config).await
handle_request(req, pact.clone(), event_send.clone(), matches.clone(), &local_addr, &config).await
)
})
})
Expand Down Expand Up @@ -162,7 +165,8 @@ pub(crate) async fn create_and_bind_https(
server_id: String,
pact: V4Pact,
addr: SocketAddr,
config: MockServerConfig
config: MockServerConfig,
matches: Arc<Mutex<Vec<MatchResult>>>
) -> anyhow::Result<(SocketAddr, oneshot::Sender<()>, mpsc::Receiver<MockServerEvent>, JoinHandle<()>)> {
if CryptoProvider::get_default().is_none() {
warn!("No TLS cryptographic provider has been configured, defaulting to the standard FIPS provider");
Expand Down Expand Up @@ -197,6 +201,7 @@ pub(crate) async fn create_and_bind_https(
let server_id = server_id.clone();
let pact = pact.clone();
let config = config.clone();
let matches = matches.clone();

select! {
connection = listener.accept() => {
Expand All @@ -219,9 +224,10 @@ pub(crate) async fn create_and_bind_https(
let event_send = ev.clone();
let config = config.clone();
let server_id = sid.clone();
let matches = matches.clone();
LOG_ID.scope(server_id, async move {
handle_mock_request_error(
handle_request(req, pact.clone(), event_send.clone(), &local_addr, &config).await
handle_request(req, pact.clone(), event_send.clone(), matches.clone(), &local_addr, &config).await
)
})
})
Expand Down Expand Up @@ -278,6 +284,7 @@ async fn handle_request(
req: Request<Incoming>,
pact: V4Pact,
event_send: Sender<MockServerEvent>,
matches: Arc<Mutex<Vec<MatchResult>>>,
local_addr: &SocketAddr,
config: &MockServerConfig
) -> Result<Response<Full<Bytes>>, InteractionError> {
Expand Down Expand Up @@ -322,8 +329,13 @@ async fn handle_request(

let match_result = match_request(&pact_request, &pact).await;

if let Err(_) = event_send.send(MockServerEvent::RequestMatch(match_result.clone())).await {
error!("Failed to send RequestMatch event");
// Record the match result synchronously before returning the response. This ensures that
// pactffi_mock_server_matched() / pactffi_mock_server_mismatches() always sees the correct
// state immediately after the client receives the HTTP response, with no race against the
// async event loop.
{
let mut guard = matches.lock().unwrap();

@JP-Ellis JP-Ellis Jul 6, 2026

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The unwrap makes me uncomfortable... While it is unlikely that the mutex gets poisoned, it would probably still be nicer to return an error if it fails.

guard.push(match_result.clone());
}

match_result_to_hyper_response(&pact_request, &match_result, local_addr, config).await
Expand Down Expand Up @@ -569,11 +581,13 @@ mod tests {

#[tokio::test]
async fn can_fetch_results_on_current_thread() {
let matches = Arc::new(Mutex::new(vec![]));
let (_addr, shutdown, mut events, handle) = create_and_bind(
"can_fetch_results_on_current_thread".to_string(),
RequestResponsePact::default().as_v4_pact().unwrap(),
([0, 0, 0, 0], 0u16).into(),
MockServerConfig::default()
MockServerConfig::default(),
matches
).await.unwrap();

shutdown.send(()).unwrap();
Expand Down Expand Up @@ -605,11 +619,13 @@ mod tests {
interactions: vec![ RequestResponseInteraction::default() ],
.. RequestResponsePact::default()
};
let matches = Arc::new(Mutex::new(vec![]));
let (addr, shutdown, mut events, handle) = create_and_bind(
"can_fetch_results_on_current_thread".to_string(),
pact.as_v4_pact().unwrap(),
([127, 0, 0, 1], 0u16).into(),
MockServerConfig::default()
MockServerConfig::default(),
matches.clone()
).await.unwrap();

let client = reqwest::ClientBuilder::new()
Expand All @@ -625,17 +641,18 @@ mod tests {
shutdown.send(()).unwrap();
let _ = handle.await;

// Should be at least 3 events
expect!(events.len()).to(be_greater_or_equal_to(3));
// Match results are now recorded directly in the mutex, not via the event channel.
// Events should contain RequestReceived plus the shutdown event (and possibly a
// ConnectionFailed on Linux once the server shuts down).
expect!(events.len()).to(be_greater_or_equal_to(2));
assert_eq!(events.recv().await.unwrap(), MockServerEvent::RequestReceived("/".to_string()));
if let MockServerEvent::RequestMatch(_) = events.recv().await.unwrap() {
// expected
} else {
panic!("Was expected a request match event");
}
// For some reason, a http2 connection returns an error once the server is shutdown on Linux
let mut events_list = vec![];
events.recv_many(&mut events_list, 2).await;
assert_eq!(events_list.last().unwrap(), &MockServerEvent::ServerShutdown);

// Verify the match result was recorded synchronously in the mutex
let guard = matches.lock().unwrap();
assert_eq!(guard.len(), 1);
}
}
18 changes: 6 additions & 12 deletions pact_mock_server/src/mock_server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -210,8 +210,6 @@ pub enum MockServerEvent {
ConnectionFailed(String),
/// Request received with path
RequestReceived(String),
/// Result of matching a request
RequestMatch(MatchResult),
/// Server is shutting down
ServerShutdown
Comment on lines 210 to 214
}
Expand Down Expand Up @@ -295,15 +293,16 @@ impl MockServer {
};

trace!(%server_id, %address, "Starting mock server");
let (address, shutdown_send, event_recv, _task_handle) = create_and_bind(server_id.clone(), pact.clone(), address, config.clone()).await?;
let matches = Arc::new(Mutex::new(vec![]));
let (address, shutdown_send, event_recv, _task_handle) = create_and_bind(server_id.clone(), pact.clone(), address, config.clone(), matches.clone()).await?;
trace!(%server_id, %address, "Mock server started");

let mut mock_server = MockServer {
id: server_id,
scheme: Default::default(),
address,
pact,
matches: Default::default(),
matches,
shutdown_tx: RefCell::new(Some(shutdown_send)),
config: config.clone(),
metrics: Default::default(),
Expand Down Expand Up @@ -333,15 +332,16 @@ impl MockServer {
};

trace!(%server_id, %address, "Starting TLS mock server");
let (address, shutdown_send, event_recv, _task_handle) = create_and_bind_https(server_id.clone(), pact.clone(), address, config.clone()).await?;
let matches = Arc::new(Mutex::new(vec![]));
let (address, shutdown_send, event_recv, _task_handle) = create_and_bind_https(server_id.clone(), pact.clone(), address, config.clone(), matches.clone()).await?;
trace!(%server_id, %address, "TLS mock server started");

let mut mock_server = MockServer {
id: server_id,
scheme: MockServerScheme::HTTPS,
address,
pact,
matches: Default::default(),
matches,
shutdown_tx: RefCell::new(Some(shutdown_send)),
config: config.clone(),
metrics: Default::default(),
Expand Down Expand Up @@ -383,7 +383,6 @@ impl MockServer {
fn start_event_loop(&mut self, mut event_recv: Receiver<MockServerEvent>) {
let server_id = self.id.clone();
let metrics = self.metrics.clone();
let matches = self.matches.clone();
let (sender, receiver) = mpsc::channel();
self.event_loop_rx = Some(receiver);

Expand All @@ -392,7 +391,6 @@ impl MockServer {

let mut total_events = 0;
let metrics = metrics.clone();
let matches = matches.clone();
while let Some(event) = event_recv.recv().await {
trace!(%server_id, ?event, "Received event");
total_events += 1;
Expand All @@ -403,10 +401,6 @@ impl MockServer {
let mut guard = metrics.lock().unwrap();
guard.add_path(path);
}
MockServerEvent::RequestMatch(result) => {
let mut guard = matches.lock().unwrap();
guard.push(result.clone());
}
MockServerEvent::ServerShutdown => {
trace!(%server_id, total_events, "Exiting mock server event loop");
break;
Expand Down
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