Client

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This section demonstrates how to establish client connections and perform RPC calls using the Elixir gRPC client.

Basic Connection and RPC

Typically, you start this client supervisor as part of your application's supervision tree:

children = [
  GRPC.Client.Supervisor
]

opts = [strategy: :one_for_one, name: MyApp.Supervisor]
Supervisor.start_link(children, opts)

You can also start it manually in scripts or test environments:

{:ok, _pid} = GRPC.Client.Supervisor.start_link()

Then connect with gRPC server:

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)

Using Interceptors

Client interceptors allow you to add logic to the request/response lifecycle, such as logging, tracing, or authentication.

iex> {:ok, channel} =
...>   GRPC.Stub.connect("localhost:50051",
...>     interceptors: [GRPC.Client.Interceptors.Logger]
...>   )
iex> request = Helloworld.HelloRequest.new(name: "Alice")
iex> {:ok, reply} = channel |> Helloworld.GreetingServer.Stub.say_unary_hello(request)

Compression and Metadata

You can specify message compression and attach default headers to all requests.

iex> {:ok, channel} =
...>   GRPC.Stub.connect("localhost:50051",
...>     compressor: GRPC.Compressor.Gzip,
...>     headers: [{"authorization", "Bearer my-token"}]
...>   )

Client Adapters

By default, GRPC.Stub.connect/2 uses the Gun adapter.
You can switch to Mint (pure Elixir HTTP/2) or other adapters as needed.

Using Mint Adapter

iex> GRPC.Stub.connect("localhost:50051",
...>   adapter: GRPC.Client.Adapters.Mint
...> )

You can configure adapter options globally via your application’s config:

# File: config/config.exs
config :grpc, GRPC.Client.Adapters.Mint,
  timeout: 10_000,
  transport_opts: [cacertfile: "/etc/ssl/certs/ca-certificates.crt"]

The accepted options are the same as Mint.HTTP.connect/4.