examples: allow configurable uds socket paths

Update unix domain socket examples to show configurable paths. It
demonstrates a way of configuring the UDS client using the ustr crate to
meet the closure capture requirements of the connector service_fn.

Fixes: hyperium#1611
Refs: hyperium#1612

examples/Cargo.toml

@@ -287,7 +287,7 @@ grpc-web = ["dep:tonic-web", "dep:bytes", "dep:http", "dep:hyper", "dep:tracing-
 tracing = ["dep:tracing", "dep:tracing-subscriber"]
 hyper-warp = ["dep:either", "dep:tower", "dep:hyper", "dep:http", "dep:http-body", "dep:warp"]
 hyper-warp-multiplex = ["hyper-warp"]
-uds = ["tokio-stream/net", "dep:tower", "dep:hyper"]
+uds = ["tokio-stream/net", "dep:tower", "dep:hyper", "dep:ustr"]
 streaming = ["tokio-stream", "dep:h2"]
 mock = ["tokio-stream", "dep:tower"]
 tower = ["dep:hyper", "dep:tower", "dep:http"]
@@ -337,6 +337,7 @@ tokio-rustls = { version = "0.24.0", optional = true }
 hyper-rustls = { version = "0.24.0", features = ["http2"], optional = true }
 rustls-pemfile = { version = "1", optional = true }
 tower-http = { version = "0.4", optional = true }
+ustr = { version = "1.0.0", optional = true }
 
 [build-dependencies]
 tonic-build = { path = "../tonic-build", features = ["prost"] }

examples/src/uds/client.rs

@@ -5,21 +5,28 @@ pub mod hello_world {
 }
 
 use hello_world::{greeter_client::GreeterClient, HelloRequest};
+use std::env;
 #[cfg(unix)]
 use tokio::net::UnixStream;
 use tonic::transport::{Endpoint, Uri};
 use tower::service_fn;
+use ustr::ustr;
 
 #[cfg(unix)]
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Path needs to be a static str due to service_fn FnMut.
+    let path = match env::var("EXAMPLE_UDS_PATH") {
+        Ok(path) => ustr(path.as_ref()).as_str(),
+        Err(_) => "/tmp/tonic/helloworld"
+    };
+    println!("Using path {}", path);
+
     // We will ignore this uri because uds do not use it
     // if your connector does use the uri it will be provided
     // as the request to the `MakeConnection`.
     let channel = Endpoint::try_from("http://[::]:50051")?
-        .connect_with_connector(service_fn(|_: Uri| {
-            let path = "/tmp/tonic/helloworld";
-
+        .connect_with_connector(service_fn(move |_: Uri| {
             // Connect to a Uds socket
             UnixStream::connect(path)
         }))

examples/src/uds/server.rs

@@ -1,6 +1,6 @@
 #![cfg_attr(not(unix), allow(unused_imports))]
 
-use std::path::Path;
+use std::{env, path::Path};
 #[cfg(unix)]
 use tokio::net::UnixListener;
 #[cfg(unix)]
@@ -43,9 +43,9 @@ impl Greeter for MyGreeter {
 #[cfg(unix)]
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let path = "/tmp/tonic/helloworld";
-
-    std::fs::create_dir_all(Path::new(path).parent().unwrap())?;
+    let path = env::var("EXAMPLE_UDS_PATH").unwrap_or("/tmp/tonic/helloworld".to_owned());
+    std::fs::create_dir_all(Path::new(&path).parent().unwrap())?;
+    println!("Using path {}", path);
 
     let greeter = MyGreeter::default();