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# grpc

[gRPC](http://www.grpc.io/) is an excellent, modern IDL and transport for
microservices.
If you're starting a greenfield project, go-kit strongly recommends gRPC as
your default transport.

One important note is that while gRPC supports streaming requests and replies,
go-kit does not. You can still use streams in your service, but their
implementation will not be able to take advantage of many go-kit features like middleware.

Using gRPC and go-kit together is very simple.

First, define your service using protobuf3.
This is explained [in gRPC documentation](http://www.grpc.io/docs/#defining-a-service).
See
[add.proto](https://github.com/go-kit/kit/blob/ec8b02591ee873433565a1ae9d317353412d1d27/examples/addsvc/pb/add.proto)
for an example.
Make sure the proto definition matches your service's go-kit (interface) definition.

Next, get the protoc compiler.

You can download pre-compiled binaries from the
[protobuf release page](https://github.com/google/protobuf/releases).
You will unzip a folder called `protoc3` with a subdirectory `bin` containing an executable.
Move that executable somewhere in your `$PATH` and you're good to go!

It can also be built from source.

```sh
brew install autoconf automake libtool
git clone https://github.com/google/protobuf
cd protobuf
./autogen.sh ; ./configure ; make ; make install
```

Then, compile your service definition, from .proto to .go.

```sh
protoc add.proto --go_out=plugins=grpc:.
```

Finally, write a tiny binding from your service definition to the gRPC definition.
It's a simple conversion from one domain to another.
See
[grpc_binding.go](https://github.com/go-kit/kit/blob/ec8b02591ee873433565a1ae9d317353412d1d27/examples/addsvc/grpc_binding.go)
for an example.

That's it!
The gRPC binding can be bound to a listener and serve normal gRPC requests.
And within your service, you can use standard go-kit components and idioms.
See [addsvc](https://github.com/go-kit/kit/tree/master/examples/addsvc) for a complete
working example with gRPC support.
And remember: go-kit services can support multiple transports simultaneously.