Provide a mechanism to inject a custom status handler

lib/grpc/adapter/cowboy.ex

@@ -153,11 +153,22 @@ defmodule GRPC.Adapter.Cowboy do
   end
 
   defp cowboy_start_args(endpoint, servers, port, opts) do
-    dispatch =
-      :cowboy_router.compile([
-        {:_, [{:_, GRPC.Adapter.Cowboy.Handler, {endpoint, servers, Enum.into(opts, %{})}}]}
-      ])
+    # Custom handler to be able to listen in the same port, more info:
+    # https://github.com/containous/traefik/issues/6211
+    {adapter_opts, opts} = Keyword.pop(opts, :adapter_opts, [])
+    status_handler = Keyword.get(adapter_opts, :status_handler)
 
+    handlers =
+      if status_handler do
+        [
+          status_handler,
+          {:_, GRPC.Adapter.Cowboy.Handler, {endpoint, servers, Enum.into(opts, %{})}}
+        ]
+      else
+        [{:_, GRPC.Adapter.Cowboy.Handler, {endpoint, servers, Enum.into(opts, %{})}}]
+      end
+
+    dispatch = :cowboy_router.compile([{:_, handlers}])
     idle_timeout = Keyword.get(opts, :idle_timeout, :infinity)
     num_acceptors = Keyword.get(opts, :num_acceptors, @default_num_acceptors)
     max_connections = Keyword.get(opts, :max_connections, @default_max_connections)

lib/grpc/server.ex

@@ -215,6 +215,9 @@ defmodule GRPC.Server do
   #   * `:cred` - a credential created by functions of `GRPC.Credential`,
   #               an insecure server will be created without this option
   #   * `:adapter` - use a custom server adapter instead of default `GRPC.Adapter.Cowboy`
+  #   * `:adapter_opts` - configuration for the specified adapter.
+  #     * `:status_handler` - adds a status handler that could be listening on HTTP/1, if necessary.
+  #                           It should follow the format defined by cowboy_router:compile/3
   @doc false
   @spec start(servers_list, non_neg_integer, Keyword.t()) :: {atom, any, non_neg_integer}
   def start(servers, port, opts \\ []) do

test/grpc/integration/server_test.exs

@@ -98,6 +98,12 @@ defmodule GRPC.Integration.ServerTest do
     end
   end
 
+  defmodule HTTP1Server do
+    def init(req, state) do
+      {:ok, :cowboy_req.reply(200, %{}, "OK", req), state}
+    end
+  end
+
   test "multiple servers works" do
     run_server([FeatureServer, HelloServer], fn port ->
       {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
@@ -111,6 +117,27 @@ defmodule GRPC.Integration.ServerTest do
     end)
   end
 
+  test "HTTP/1 status handler can be started along a gRPC server" do
+    status_handler = {"/status", HTTP1Server, []}
+
+    run_server(
+      [HelloServer],
+      fn port ->
+        {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
+        req = Helloworld.HelloRequest.new(name: "Elixir")
+        {:ok, reply} = channel |> Helloworld.Greeter.Stub.say_hello(req)
+        assert reply.message == "Hello, Elixir"
+
+        {:ok, conn_pid} = :gun.open('localhost', port)
+        stream_ref = :gun.get(conn_pid, "/status")
+
+        assert_receive {:gun_response, ^conn_pid, ^stream_ref, :nofin, 200, _headers}
+      end,
+      0,
+      adapter_opts: [status_handler: status_handler]
+    )
+  end
+
   test "returns appropriate error for unary requests" do
     run_server([HelloErrorServer], fn port ->
       {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")

test/support/integration_test_case.ex

@@ -9,8 +9,8 @@ defmodule GRPC.Integration.TestCase do
     end
   end
 
-  def run_server(servers, func, port \\ 0) do
-    {:ok, _pid, port} = GRPC.Server.start(servers, port)
+  def run_server(servers, func, port \\ 0, opts \\ []) do
+    {:ok, _pid, port} = GRPC.Server.start(servers, port, opts)
 
     try do
       func.(port)