feat(codec): compression support (#692)

* Initial compression support

* Support configuring compression on `Server`

* Minor clean up

* Test that compression is actually happening

* Clean up some todos

* channels compressing requests

* Move compression to be on the codecs

* Test sending compressed request to server that doesn't support it

* Clean up a bit

* Compress server streams

* Compress client streams

* Bidirectional streaming compression

* Handle receiving unsupported encoding

* Clean up

* Add note to future self

* Support disabling compression for individual responses

* Add docs

* Add compression examples

* Disable compression behind feature flag

* Add some docs

* Make flate2 optional dependency

* Fix docs wording

* Format

* Reply with which encodings are supported

* Convert tests to use mocked io

* Fix lints

* Use separate counters

* Don't make a long stream

* Address review feedback

examples/src/compression/client.rs

@@ -0,0 +1,27 @@
+use hello_world::greeter_client::GreeterClient;
+use hello_world::HelloRequest;
+use tonic::transport::Channel;
+
+pub mod hello_world {
+    tonic::include_proto!("helloworld");
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let channel = Channel::builder("http://[::1]:50051".parse().unwrap())
+        .connect()
+        .await
+        .unwrap();
+
+    let mut client = GreeterClient::new(channel).send_gzip().accept_gzip();
+
+    let request = tonic::Request::new(HelloRequest {
+        name: "Tonic".into(),
+    });
+
+    let response = client.say_hello(request).await?;
+
+    dbg!(response);
+
+    Ok(())
+}

examples/src/compression/server.rs

@@ -0,0 +1,40 @@
+use tonic::{transport::Server, Request, Response, Status};
+
+use hello_world::greeter_server::{Greeter, GreeterServer};
+use hello_world::{HelloReply, HelloRequest};
+
+pub mod hello_world {
+    tonic::include_proto!("helloworld");
+}
+
+#[derive(Default)]
+pub struct MyGreeter {}
+
+#[tonic::async_trait]
+impl Greeter for MyGreeter {
+    async fn say_hello(
+        &self,
+        request: Request<HelloRequest>,
+    ) -> Result<Response<HelloReply>, Status> {
+        println!("Got a request from {:?}", request.remote_addr());
+
+        let reply = hello_world::HelloReply {
+            message: format!("Hello {}!", request.into_inner().name),
+        };
+        Ok(Response::new(reply))
+    }
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let addr = "[::1]:50051".parse().unwrap();
+    let greeter = MyGreeter::default();
+
+    println!("GreeterServer listening on {}", addr);
+
+    let service = GreeterServer::new(greeter).send_gzip().accept_gzip();
+
+    Server::builder().add_service(service).serve(addr).await?;
+
+    Ok(())
+}