alamb commented on code in PR #4727:
URL: https://github.com/apache/arrow-rs/pull/4727#discussion_r1303407710
##########
arrow-flight/src/decode.rs:
##########
@@ -98,9 +109,36 @@ impl FlightRecordBatchStream {
{
Self {
inner: FlightDataDecoder::new(inner),
+ headers: MetadataMap::default(),
+ trailers: None,
+ }
+ }
+
+ /// Record response headers.
+ pub fn with_headers(self, headers: MetadataMap) -> Self {
+ Self { headers, ..self }
+ }
+
+ /// Record response trailers.
+ pub fn with_trailers(self, trailers: LazyTrailers) -> Self {
+ Self {
+ trailers: Some(trailers),
+ ..self
}
}
+ /// Headers attached to this stream.
+ pub fn headers(&self) -> &MetadataMap {
+ &self.headers
+ }
+
+ /// Trailers attached to this stream.
+ ///
+ /// This is only filled when the entire stream was consumed.
Review Comment:
```suggestion
/// Note that this will return `None` until the entire stream is
consumed.
/// Only after calling `next()` returns `None`, might any available
trailers be returned.
```
##########
arrow-flight/src/client.rs:
##########
@@ -204,16 +204,14 @@ impl FlightClient {
pub async fn do_get(&mut self, ticket: Ticket) ->
Result<FlightRecordBatchStream> {
Review Comment:
There are other methods on this client that might be interested in server
headers/trailers -- like do_exchange and do_put. Maybe we can file a ticket to
track adding support for them too
##########
arrow-flight/tests/client.rs:
##########
@@ -158,18 +159,39 @@ async fn test_do_get() {
let response = vec![Ok(batch.clone())];
test_server.set_do_get_response(response);
- let response_stream = client
+ let mut response_stream = client
.do_get(ticket.clone())
.await
.expect("error making request");
+ assert_eq!(
+ response_stream
+ .headers()
+ .get("test-resp-header")
+ .expect("header exists")
+ .to_str()
+ .unwrap(),
+ "some_val",
+ );
+
let expected_response = vec![batch];
- let response: Vec<_> = response_stream
+ let response: Vec<_> = (&mut response_stream)
Review Comment:
I think it would be good to assert that `response_stream.trailers()` returns
`None` prior to stream exhaustion
##########
arrow-flight/src/trailers.rs:
##########
@@ -0,0 +1,92 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::{
+ pin::Pin,
+ sync::{Arc, Mutex},
+ task::{Context, Poll},
+};
+
+use futures::{ready, FutureExt, Stream, StreamExt};
+use tonic::{metadata::MetadataMap, Status, Streaming};
+
+/// Extract trailers from [`Streaming`] [tonic] response.
Review Comment:
I think expanding on the fact that returns something with inner mutability
that is updated when the stream is exhausted (as opposed to `extract_headers`
which returns a value immediately) would help
Maybe we could call it `extract_lazy_trailers` to call attention to the fact
it behaves differently to extract_headers
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