# gRPC Elixir
[](https://github.com/elixir-grpc/grpc/actions/workflows/ci.yml)
[](https://hex.pm/packages/grpc)
[](https://hexdocs.pm/grpc/)
[](https://github.com/elixir-grpc/grpc/blob/master/LICENSE)
[](https://hex.pm/packages/grpc)
[](https://github.com/elixir-grpc/grpc/commits/master)
**gRPC Elixir** is a full-featured Elixir implementation of the [gRPC](https://grpc.io) protocol, supporting unary and streaming RPCs, interceptors, HTTP transcoding, and TLS. This version adopts a unified stream-based model for all types of calls.
## Table of contents
- [Installation](#installation)
- [Protobuf Code Generation](#protobuf-code-generation)
- [Server Implementation](#server-implementation)
- [Unary RPC using Stream API](#unary-rpc-using-stream-api)
- [Server-Side Streaming](#server-side-streaming)
- [Bidirectional Streaming](#bidirectional-streaming)
- [Application Startup](#application-startup)
- [Client Usage](#client-usage)
- [HTTP Transcoding](#http-transcoding)
- [CORS](#cors)
- [Features](#features)
- [Benchmark](#benchmark)
- [Contributing](#contributing)
## Installation
The package can be installed as:
```elixir
def deps do
[
{:grpc, "~> 0.11"},
{:protobuf, "~> 0.14"}, # optional for import wellknown google types
{:grpc_reflection, "~> 0.2"} # optional enable grpc reflection
]
end
```
## Protobuf Code Generation
Use `protoc` with [protobuf elixir plugin](https://github.com/elixir-protobuf/protobuf) or using [protobuf_generate](https://hexdocs.pm/protobuf_generate/readme.html) hex package to generate the necessary files.
1. Write your protobuf file:
```protobuf
syntax = "proto3";
package helloworld;
// The request message containing the user's name.
message HelloRequest {
string name = 1;
}
// The response message containing the greeting
message HelloReply {
string message = 1;
}
// The greeting service definition.
service GreetingServer {
rpc SayUnaryHello (HelloRequest) returns (HelloReply) {}
rpc SayServerHello (HelloRequest) returns (stream HelloReply) {}
rpc SayBidStreamHello (stream HelloRequest) returns (stream HelloReply) {}
}
```
2. Compile protos (protoc + elixir plugin):
```bash
protoc --elixir_out=plugins=grpc:./lib -I./priv/protos helloworld.proto
```
## Server Implementation
All RPC calls must be implemented using the stream-based API, even for unary requests.
### Unary RPC using Stream API
```elixir
defmodule HelloworldStreams.Server do
use GRPC.Server, service: Helloworld.GreetingServer.Service
alias GRPC.Stream
alias Helloworld.HelloRequest
alias Helloworld.HelloReply
@spec say_unary_hello(HelloRequest.t(), GRPC.Server.Stream.t()) :: any()
def say_unary_hello(request, _materializer) do
GRPC.Stream.unary(request)
|> GRPC.Stream.map(fn %HelloReply{} = reply ->
%HelloReply{message: "[Reply] #{reply.message}"}
end)
|> GRPC.Stream.run()
end
end
```
### Server-Side Streaming
```elixir
def say_server_hello(request, materializer) do
Stream.repeatedly(fn ->
index = :rand.uniform(10)
%HelloReply{message: "[#{index}] Hello #{request.name}"}
end)
|> Stream.take(10)
|> GRPC.Stream.from()
|> GRPC.Stream.run_with(materializer)
end
```
### Bidirectional Streaming
```elixir
@spec say_bid_stream_hello(Enumerable.t(), GRPC.Server.Stream.t()) :: any()
def say_bid_stream_hello(request, materializer) do
output_stream =
Stream.repeatedly(fn ->
index = :rand.uniform(10)
%HelloReply{message: "[#{index}] Server response"}
end)
GRPC.Stream.from(request, join_with: output_stream)
|> GRPC.Stream.map(fn
%HelloRequest{name: name} -> %HelloReply{message: "Welcome #{name}"}
other -> other
end)
|> GRPC.Stream.run_with(materializer)
end
```
__💡__ The Stream API supports composable stream transformations via `ask`, `map`, `run` and others functions, enabling clean and declarative stream pipelines. For a complete list of available operators see [here](lib/grpc/stream.ex).
## Application Startup
Add the server supervisor to your application's supervision tree:
```elixir
defmodule Helloworld.Application do
@ false
use Application
@impl true
def start(_type, _args) do
children = [
GrpcReflection,
{
GRPC.Server.Supervisor, [
endpoint: Helloworld.Endpoint,
port: 50051,
start_server: true,
# adapter_opts: [# any adapter-specific options like tls configuration....]
]
}
]
opts = [strategy: :one_for_one, name: Helloworld.Supervisor]
Supervisor.start_link(children, opts)
end
end
```
# Client Usage
```elixir
iex> {:ok, channel} = GRPC.Stub.connect("localhost:50051")
iex> request = Helloworld.HelloRequest.new(name: "grpc-elixir")
iex> {:ok, reply} = channel |> Helloworld.GreetingServer.Stub.say_unary_hello(request)
# With interceptors
iex> {:ok, channel} = GRPC.Stub.connect("localhost:50051", interceptors: [GRPC.Client.Interceptors.Logger])
...
```
Check the [examples](examples) and [interop](interop) directories in the project's source code for some examples.
## Client Adapter and Configuration
The default adapter used by `GRPC.Stub.connect/2` is `GRPC.Client.Adapter.Gun`. Another option is to use `GRPC.Client.Adapters.Mint` instead, like so:
```elixir
GRPC.Stub.connect("localhost:50051",
# Use Mint adapter instead of default Gun
adapter: GRPC.Client.Adapters.Mint
)
```
The `GRPC.Client.Adapters.Mint` adapter accepts custom configuration. To do so, you can configure it from your mix application via:
```elixir
# File: your application's config file.
config :grpc, GRPC.Client.Adapters.Mint, custom_opts
```
The accepted options for configuration are the ones listed on [Mint.HTTP.connect/4](https://hexdocs.pm/mint/Mint.HTTP.html#connect/4-options)
### **HTTP Transcoding**
1. Adding [grpc-gateway annotations](https://cloud.google.com/endpoints/docs/grpc/transcoding) to your protobuf file definition:
```protobuf
import "google/api/annotations.proto";
import "google/protobuf/timestamp.proto";
package helloworld;
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {
option (google.api.http) = {
get: "/v1/greeter/{name}"
};
}
rpc SayHelloFrom (HelloRequestFrom) returns (HelloReply) {
option (google.api.http) = {
post: "/v1/greeter"
body: "*"
};
}
}
```
2. Add protoc plugin dependency and compile your protos using [protobuf_generate](https://github.com/drowzy/protobuf_generate) hex [package](https://hex.pm/packages/protobuf_generate):
In mix.exs:
```elixir
def deps do
[
{:grpc, "~> 0.11"},
{:protobuf_generate, "~> 0.1.3"}
]
end
```
And in your terminal:
```shell
mix protobuf.generate \
--include-path=priv/proto \
--include-path=deps/googleapis \
--generate-descriptors=true \
--output-path=./lib \
--plugins=ProtobufGenerate.Plugins.GRPCWithOptions \
google/api/annotations.proto google/api/http.proto helloworld.proto
```
3. Enable http_transcode option in your Server module
```elixir
defmodule Helloworld.Greeter.Server do
use GRPC.Server,
service: Helloworld.Greeter.Service,
http_transcode: true
# callback implementations...
end
```
See full application code in [helloworld_transcoding](examples/helloworld_transcoding) example.
### **CORS**
When accessing gRPC from a browser via HTTP transcoding or gRPC-Web, CORS headers may be required for the browser to allow access to the gRPC endpoint. Adding CORS headers can be done by using `GRPC.Server.Interceptors.CORS` as an interceptor in your `GRPC.Endpoint` module, configuring it as described in the module documentation:
Example:
```elixir
# Define your endpoint
defmodule Helloworld.Endpoint do
use GRPC.Endpoint
intercept GRPC.Server.Interceptors.Logger
intercept GRPC.Server.Interceptors.CORS, allow_origin: "mydomain.io"
run Helloworld.Greeter.Server
end
```
## Features
- Various kinds of RPC:
- [Unary](https://grpc.io/docs/what-is-grpc/core-concepts/#unary-rpc)
- [Server-streaming](https://grpc.io/docs/what-is-grpc/core-concepts/#server-streaming-rpc)
- [Client-streaming](https://grpc.io/docs/what-is-grpc/core-concepts/#client-streaming-rpc)
- [Bidirectional-streaming](https://grpc.io/docs/what-is-grpc/core-concepts/#bidirectional-streaming-rpc)
- [HTTP Transcoding](https://cloud.google.com/endpoints/docs/grpc/transcoding)
- [TLS Authentication](https://grpc.io/docs/guides/auth/#supported-auth-mechanisms)
- [Error Handling](https://grpc.io/docs/guides/error/)
- [Interceptors](https://grpc.io/docs/guides/interceptors/)
- [Connection Backoff](https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md)
- [Data Compression](https://grpc.io/docs/guides/compression/)
- [gRPC Reflection](https://github.com/elixir-grpc/grpc-reflection)
## Benchmark
1. [Simple benchmark](examples/helloworld/README.md#Benchmark) by using [ghz](https://ghz.sh/)
2. [Benchmark](benchmark) followed by official spec
## Contributing
Your contributions are welcome!
Please open issues if you have questions, problems and ideas. You can create pull
requests directly if you want to fix little bugs, add small features and so on.
But you'd better use issues first if you want to add a big feature or change a
lot of code.
