Add gRPC reflection support to arrow flight

Addresses #1706, adding a
constant to the gRPC generated code so it is possible to include the
Flight and Flight SQL APIs in a `tonic-reflection` service.

Testing:

```
grpcurl --plaintext localhost:8082 list
```

arrow-flight/Cargo.toml

@@ -78,6 +78,7 @@ tracing-log = { version = "0.2" }
 tracing-subscriber = { version = "0.3.1", default-features = false, features = ["ansi", "env-filter", "fmt"] }
 tokio = { version = "1.0", default-features = false, features = ["macros", "rt", "rt-multi-thread"] }
 tokio-stream = { version = "0.1", features = ["net"] }
+tonic-reflection = "0.12.3"
 tower = { version = "0.5.0", features = ["util"] }
 uuid = { version = "1.10.0", features = ["v4"] }
 

arrow-flight/gen/src/main.rs

@@ -29,6 +29,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         // protoc in Ubuntu builder needs this option
         .protoc_arg("--experimental_allow_proto3_optional")
         .out_dir("src")
+        .file_descriptor_set_path("src/flight_descriptor.bin")
         .compile_protos_with_config(prost_config(), &[proto_path], &[proto_dir])?;
 
     // read file contents to string
@@ -52,6 +53,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         // protoc in Ubuntu builder needs this option
         .protoc_arg("--experimental_allow_proto3_optional")
         .out_dir("src/sql")
+        .file_descriptor_set_path("src/sql/flight_sql_descriptor.bin")
         .compile_protos_with_config(prost_config(), &[proto_path], &[proto_dir])?;
 
     // read file contents to string

arrow-flight/src/lib.rs

@@ -58,12 +58,25 @@ mod gen {
     // Since this file is auto-generated, we suppress all warnings
     #![allow(missing_docs)]
     include!("arrow.flight.protocol.rs");
+
+    /// The descriptor used for making the Arrow Flight gRPC API available for [gRPC
+    /// reflection](https://grpc.io/docs/guides/reflection/).
+    ///
+    /// ```
+    /// let reflection_server = tonic_reflection::server::Builder::configure()
+    ///    .register_encoded_file_descriptor_set(arrow_flight::flight_descriptor::FILE_DESCRIPTOR_SET)
+    ///    .build_v1()
+    ///    .unwrap();
+    /// ```
+    pub const FILE_DESCRIPTOR_SET: &[u8] = include_bytes!("flight_descriptor.bin");
 }
 
 /// Defines a `Flight` for generation or retrieval.
 pub mod flight_descriptor {
     use super::gen;
     pub use gen::flight_descriptor::DescriptorType;
+
+    pub use gen::FILE_DESCRIPTOR_SET;
 }
 
 /// Low Level [tonic] [`FlightServiceClient`](gen::flight_service_client::FlightServiceClient).

arrow-flight/src/sql/mod.rs

@@ -49,6 +49,17 @@ mod gen {
     // Since this file is auto-generated, we suppress all warnings
     #![allow(missing_docs)]
     include!("arrow.flight.protocol.sql.rs");
+
+    /// The descriptor used for making the Arrow Flight SQL gRPC API available for [gRPC
+    /// reflection](https://grpc.io/docs/guides/reflection/).
+    ///
+    /// ```
+    /// let reflection_server = tonic_reflection::server::Builder::configure()
+    ///    .register_encoded_file_descriptor_set(arrow_flight::sql::FILE_DESCRIPTOR_SET)
+    ///    .build_v1()
+    ///    .unwrap();
+    /// ```
+    pub const FILE_DESCRIPTOR_SET: &[u8] = include_bytes!("flight_sql_descriptor.bin");
 }
 
 pub use gen::action_end_transaction_request::EndTransaction;
@@ -109,6 +120,7 @@ pub use gen::TicketStatementQuery;
 pub use gen::UpdateDeleteRules;
 pub use gen::XdbcDataType;
 pub use gen::XdbcDatetimeSubcode;
+pub use gen::FILE_DESCRIPTOR_SET;
 
 pub mod client;
 pub mod metadata;