Use append() for writing telemetry lock to file (#585)

Otherwise we see spurious race conditions where the file is opened twice and one thread is overwriting to the start of the file.

And lock cbindgen version for CI.

ddtelemetry/src/worker/http_client.rs

@@ -5,7 +5,7 @@ use ddcommon::HttpRequestBuilder;
 use http::{Request, Response};
 use hyper::Body;
 use std::{
- fs::File,
+ fs::OpenOptions,
  future::Future,
  io::Write,
  pin::Pin,
@@ -46,7 +46,11 @@ pub fn from_config(c: &Config) -> Box<dyn HttpClient + Sync + Send> {
  .expect("file urls should always have been encoded in authority");
  return Box::new(MockClient {
  file: Arc::new(Mutex::new(Box::new(
- File::create(file_path).expect("Couldn't open mock client file"),
+ OpenOptions::new()
+ .create(true)
+ .append(true)
+ .open(file_path.as_path())
+ .expect("Couldn't open mock client file"),
  ))),
  });
  }
@@ -78,12 +82,12 @@ impl HttpClient for MockClient {
  fn request(&self, mut req: Request<hyper::Body>) -> ResponseFuture {
  let s = self.clone();
  Box::pin(async move {
- let body = hyper::body::to_bytes(req.body_mut()).await?;
+ let mut body = hyper::body::to_bytes(req.body_mut()).await?.to_vec();
+ body.push(b'\n');
 
  {
  let mut writer = s.file.lock().expect("mutex poisoned");
  writer.write_all(body.as_ref()).unwrap();
- writer.write_all(b"\n").unwrap();
  }
 
  Ok(Response::builder()

tools/docker/Dockerfile.build

@@ -60,7 +60,7 @@ ENV PATH="/root/.cargo/bin:$PATH"
 ARG CARGO_BUILD_INCREMENTAL
 ARG CARGO_NET_RETRY
 ENV CARGO_NET_RETRY="${CARGO_NET_RETRY}"
-RUN cargo install cbindgen && cargo install bindgen-cli --locked && rm -rf /root/.cargo/registry /root/.cargo/git
+RUN cargo install cbindgen --version "^0.26" && cargo install bindgen-cli --locked && rm -rf /root/.cargo/registry /root/.cargo/git
 
 FROM alpine_aws_cli as alpine_builder
 COPY --from=alpine_cbindgen /root/.cargo/bin/cbindgen /usr/local/bin/cbindgen