Add tonic for opentelemetry-otlp (open-telemetry#352)

Add support for the [tonic](https://github.com/hyperium/tonic) implementation of the gRPC transport layer to `opentelemetry-otlp`.

- Use tonic as the underlying gRPC transport layer (default)
- Optional: TLS support using rustls
- Optional: Use the platform's native certificate store
- Optional: Use an async client

Author: realtimetodie

CONTRIBUTING.md

@@ -15,7 +15,14 @@ join the meeting or get in touch on
 
 ### Prerequisites
 
-Crate `opentelemetry-otlp` uses gRPC. So you will need the following to build:
+Crate `opentelemetry-otlp` uses gRPC + Protocol Buffers.<br>
+You can provide the protocol compiler protoc path programmatically (only works with tonic) or build it from source
+
+```sh
+export PROTOC=$(which protoc)
+```
+
+Prerequisites to build the protocol compiler protoc from source
 
 - [protoc](https://github.com/protocolbuffers/protobuf)
 - [cmake](https://cmake.org)

opentelemetry-otlp/Cargo.toml

@@ -16,22 +16,34 @@ license = "Apache-2.0"
 edition = "2018"
 build = "build.rs"
 
+[lib]
+doctest = false
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
 async-trait = "0.1"
 futures = "0.3"
-grpcio = "0.6"
+grpcio = { version = "0.7", optional = true }
 opentelemetry = { version = "0.10", default-features = false, features = ["trace"], path = "../opentelemetry" }
-protobuf = "2.18"
+prost = { version = "0.6", optional = true }
+protobuf = { version = "2.18", optional = true }
 thiserror = "1.0"
+tonic = { package = "tonic", version = "0.3", optional = true }
+tokio = { version = "0.2", features = ["full"], optional = true }
 
 [features]
+async = ["default"]
+default = ["tonic", "tonic-build", "prost", "tokio"]
+grpc-sys = ["grpcio", "protobuf", "protobuf-codegen", "protoc-grpcio"]
+tls = ["tonic/tls"]
+tls-roots = ["tls", "tonic/tls-roots"]
 openssl = ["grpcio/openssl"]
 openssl-vendored = ["grpcio/openssl-vendored"]
 
 [build-dependencies]
-protobuf-codegen = "2.16"
-protoc-grpcio = "2.0"
+protobuf-codegen = { version = "2.16", optional = true }
+protoc-grpcio = { version = "2.0", optional = true }
+tonic-build = { version = "0.3", optional = true }

opentelemetry-otlp/README.md

@@ -57,17 +57,33 @@ fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
     Ok(())
 }
 ```
+
+## Options
+
+Multiple gRPC transport layers are available. [`tonic`](https://crates.io/crates/tonic) is the default gRPC transport 
+layer and is enabled by default. [`grpcio`](https://crates.io/crates/grpcio) is optional.
+
+| gRPC transport layer | [hyperium/tonic](https://github.com/hyperium/tonic) | [tikv/grpc-rs](https://github.com/tikv/grpc-rs) |
+|---|---|---|
+| Feature | --features=default | --features=grpc-sys |
+| gRPC library | [`tonic`](https://crates.io/crates/tonic) | [`grpcio`](https://crates.io/crates/grpcio) |
+| Transport | [hyperium/hyper](https://github.com/hyperium/hyper) (Rust) | [grpc/grpc](https://github.com/grpc/grpc) (C++ binding) |
+| TLS support | yes | yes |
+| TLS library | rustls | OpenSSL |
+| TLS optional | yes | yes |
+| Supported .proto generator | [`prost`](https://crates.io/crates/prost) | [`prost`](https://crates.io/crates/prost), [`protobuf`](https://crates.io/crates/protobuf) |
+
 ## Performance
 
 For optimal performance, a batch exporter is recommended as the simple
-exporter will export each span synchronously on drop. You can enable the
-[`tokio`] or [`async-std`] features to have a batch exporter configured for
-you automatically for either executor when you install the pipeline.
+exporter will export each span synchronously on drop. Enable a runtime
+to have a batch exporter configured automatically for either executor
+when using the pipeline.
 
 ```toml
 [dependencies]
-opentelemetry = { version = "*", features = ["tokio"] }
-opentelemetry-otlp = "*"
+opentelemetry = { version = "*", features = ["async-std"] }
+opentelemetry-otlp = { version = "*", features = ["grpc-sys"] }
 ```
 
 [`tokio`]: https://tokio.rs
@@ -83,25 +99,31 @@ Example showing how to override all configuration options. See the
 ```rust
 use opentelemetry::{KeyValue, Tracer};
 use opentelemetry::sdk::{trace, IdGenerator, Resource, Sampler};
-use opentelemetry_otlp::{Compression, Credentials, Protocol};
+use opentelemetry_otlp::{Protocol};
 use std::time::Duration;
+use tonic::{
+    metadata::*,
+    transport::{Certificate, ClientTlsConfig},
+};
 
 fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
-    let headers = vec![("X-Custom".to_string(), "Custom-Value".to_string())]
-        .into_iter()
-        .collect();
+    let cert = std::fs::read_to_string("ca.pem")?;
+
+    let mut map = MetadataMap::with_capacity(3);
+
+    map.insert("x-host", "example.com".parse().unwrap());
+    map.insert("x-number", "123".parse().unwrap());
+    map.insert_bin("trace-proto-bin", MetadataValue::from_bytes(b"[binary data]"));
 
     let (tracer, _uninstall) = opentelemetry_otlp::new_pipeline()
         .with_endpoint("localhost:55680")
         .with_protocol(Protocol::Grpc)
-        .with_headers(headers)
-        .with_compression(Compression::Gzip)
+        .with_metadata(map)
         .with_timeout(Duration::from_secs(3))
-        .with_completion_queue_count(2)
-        .with_credentials(Credentials {
-            cert: "tls.cert".to_string(),
-            key: "tls.key".to_string(),
-        })
+        .with_tls_config(ClientTlsConfig::new()
+            .ca_certificate(Certificate::from_pem(&cert))
+            .domain_name("example.com".to_string())
+        )
         .with_trace_config(
             trace::config()
                 .with_default_sampler(Sampler::AlwaysOn)
@@ -120,16 +142,3 @@ fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
     Ok(())
 }
 ```
-
-## Feature flags
-
-By default `opentelemetry-otlp` uses `boringssl` for grpc crypto. You can switch
-this to use `openssl` by enabling the `openssl` feature:
-
-```toml
-[dependencies]
-opentelemetry-otlp = { version = "*", features = ["openssl"] }
-```
-
-If you would like to use a vendored `openssl` version, use the `openssl-vendored` feature.
-For more info, see https://github.com/tikv/grpc-rs#feature-openssl-and-openssl-vendored.

opentelemetry-otlp/build.rs

@@ -1,9 +1,33 @@
+#[cfg(all(feature = "grpc-sys", not(feature = "tonic")))]
 extern crate protoc_grpcio;
 
+#[cfg(all(feature = "grpc-sys", not(feature = "tonic")))]
 use protobuf_codegen::Customize;
+
+#[cfg(all(feature = "grpc-sys", not(feature = "tonic")))]
 use protoc_grpcio::compile_grpc_protos;
 
 fn main() {
+    #[cfg(feature = "tonic")]
+    tonic_build::configure()
+        .build_server(false)
+        .build_client(true)
+        .format(false)
+        .compile(
+            &[
+                "src/proto/opentelemetry-proto/opentelemetry/proto/common/v1/common.proto",
+                "src/proto/opentelemetry-proto/opentelemetry/proto/resource/v1/resource.proto",
+                "src/proto/opentelemetry-proto/opentelemetry/proto/trace/v1/trace.proto",
+                "src/proto/opentelemetry-proto/opentelemetry/proto/trace/v1/trace_config.proto",
+                "src/proto/opentelemetry-proto/opentelemetry/proto/collector/trace/v1/trace_service.proto",
+                "src/proto/opentelemetry-proto/opentelemetry/proto/metrics/v1/metrics.proto",
+                "src/proto/opentelemetry-proto/opentelemetry/proto/collector/metrics/v1/metrics_service.proto",
+            ],
+            &["src/proto/opentelemetry-proto"],
+        )
+        .expect("Error generating protobuf");
+
+    #[cfg(all(feature = "grpc-sys", not(feature = "tonic")))]
     compile_grpc_protos(
         &[
             "src/proto/opentelemetry-proto/opentelemetry/proto/common/v1/common.proto",
@@ -15,12 +39,12 @@ fn main() {
             "src/proto/opentelemetry-proto/opentelemetry/proto/collector/metrics/v1/metrics_service.proto",
         ],
         &["src/proto/opentelemetry-proto/"],
-        "src/proto",
+        "src/proto/grpcio",
         Some(Customize {
             expose_fields: Some(true),
             serde_derive: Some(true),
             ..Default::default()
         }),
-    )
-    .expect("Error generating protobuf");
+        )
+        .expect("Error generating protobuf");
 }