Add details field to gRPC error struct

Adds a details field of type [any()] to the error struct and updates the transport layer to properly encode + decode them.
brexhq · Oct 19, 2021 · f4fd1e5 · f4fd1e5
1 parent 2aff9a8
commit f4fd1e5
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Showing 6 changed files with 137 additions and 30 deletions.
diff --git a/lib/grpc/adapter/cowboy/handler.ex b/lib/grpc/adapter/cowboy/handler.ex
@@ -54,7 +54,7 @@ defmodule GRPC.Adapter.Cowboy.Handler do
       {:cowboy_loop, req, %{pid: pid, handling_timer: timer_ref}}
     else
       {:error, error} ->
-        trailers = HTTP2.server_trailers(error.status, error.message)
+        trailers = HTTP2.server_trailers(error.status, error.message, error.details)
         req = send_error_trailers(req, trailers)
         {:ok, req, state}
     end
@@ -255,8 +255,13 @@ defmodule GRPC.Adapter.Cowboy.Handler do
   end
 
   def info({:handling_timeout, _}, req, state = %{pid: pid}) do
-    error = %RPCError{status: GRPC.Status.deadline_exceeded(), message: "Deadline expired"}
-    trailers = HTTP2.server_trailers(error.status, error.message)
+    error = %RPCError{
+      status: GRPC.Status.deadline_exceeded(),
+      message: "Deadline expired",
+      details: []
+    }
+
+    trailers = HTTP2.server_trailers(error.status, error.message, error.details)
     exit_handler(pid, :timeout)
     req = send_error_trailers(req, trailers)
     {:stop, req, state}
@@ -280,25 +285,36 @@ defmodule GRPC.Adapter.Cowboy.Handler do
 
   # expected error raised from user to return error immediately
   def info({:EXIT, pid, {%RPCError{} = error, _stacktrace}}, req, state = %{pid: pid}) do
-    trailers = HTTP2.server_trailers(error.status, error.message)
+    trailers = HTTP2.server_trailers(error.status, error.message, error.details)
     exit_handler(pid, :rpc_error)
     req = send_error_trailers(req, trailers)
     {:stop, req, state}
   end
 
   # unknown error raised from rpc
   def info({:EXIT, pid, {:handle_error, _kind}}, req, state = %{pid: pid}) do
-    error = %RPCError{status: GRPC.Status.unknown(), message: "Internal Server Error"}
-    trailers = HTTP2.server_trailers(error.status, error.message)
+    error = %RPCError{
+      status: GRPC.Status.unknown(),
+      message: "Internal Server Error",
+      details: []
+    }
+
+    trailers = HTTP2.server_trailers(error.status, error.message, error.details)
     exit_handler(pid, :error)
     req = send_error_trailers(req, trailers)
     {:stop, req, state}
   end
 
   def info({:EXIT, pid, {reason, stacktrace}}, req, state = %{pid: pid}) do
     Logger.error(Exception.format(:error, reason, stacktrace))
-    error = %RPCError{status: GRPC.Status.unknown(), message: "Internal Server Error"}
-    trailers = HTTP2.server_trailers(error.status, error.message)
+
+    error = %RPCError{
+      status: GRPC.Status.unknown(),
+      message: "Internal Server Error",
+      details: []
+    }
+
+    trailers = HTTP2.server_trailers(error.status, error.message, error.details)
     exit_handler(pid, reason)
     req = send_error_trailers(req, trailers)
     {:stop, req, state}
@@ -428,7 +444,7 @@ defmodule GRPC.Adapter.Cowboy.Handler do
 
   defp send_error(req, %{pid: pid}, msg) do
     error = RPCError.exception(status: :internal, message: msg)
-    trailers = HTTP2.server_trailers(error.status, error.message)
+    trailers = HTTP2.server_trailers(error.status, error.message, error.details)
 
     exit_handler(pid, :rpc_error)
     send_error_trailers(req, trailers)

diff --git a/lib/grpc/adapter/gun.ex b/lib/grpc/adapter/gun.ex
@@ -196,7 +196,11 @@ defmodule GRPC.Adapter.Gun do
               {:error,
                GRPC.RPCError.exception(
                  String.to_integer(headers["grpc-status"]),
-                 headers["grpc-message"]
+                 headers["grpc-message"],
+                 # TODO: stop assuming details is a list of strings only
+                 headers["grpc-details"]
+                 |> String.split(",")
+                 |> Enum.filter(fn x -> x != "" end)
                )}
           end
         else
@@ -215,7 +219,11 @@ defmodule GRPC.Adapter.Gun do
             {:error,
              GRPC.RPCError.exception(
                String.to_integer(headers["grpc-status"]),
-               headers["grpc-message"]
+               headers["grpc-message"],
+               # TODO: stop assuming details is a list of strings only
+               headers["grpc-details"]
+               |> String.split(",")
+               |> Enum.filter(fn x -> x != "" end)
              )}
           else
             {:response, headers, :nofin}

diff --git a/lib/grpc/error.ex b/lib/grpc/error.ex
@@ -5,28 +5,30 @@ defmodule GRPC.RPCError do
       # server side
       raise GRPC.RPCError, status: :unknown # preferred
       raise GRPC.RPCError, status: GRPC.Status.unknown, message: "error message"
+      raise GRPC.RPCError, status: GRPC.Status.unknown, details: [Google.Rpc.LocalizedMessage.new!(locale: “en-US”, message: “User friendly string.”)]
 
       # client side
       {:error, error} = Your.Stub.unary_call(channel, request)
   """
 
-  defexception [:status, :message]
-  @type t :: %__MODULE__{status: GRPC.Status.t(), message: String.t()}
+  defexception [:status, :message, :details]
+  @type t :: %__MODULE__{status: GRPC.Status.t(), message: String.t(), details: [any()]}
 
   alias GRPC.Status
 
-  @spec exception(Status.t(), String.t()) :: t
+  @spec exception(Status.t(), String.t(), [any()]) :: t
   def new(status) when is_atom(status) do
     exception(status: status)
   end
 
   def exception(args) when is_list(args) do
     error = parse_args(args, %__MODULE__{})
 
-    if error.message do
-      error
-    else
-      Map.put(error, :message, status_message(error.status))
+    cond do
+      error.message && error.details -> error
+      error.details -> Map.put(error, :message, status_message(error.status))
+      error.message -> Map.put(error, :details, [])
+      true -> error |> Map.put(:message, status_message(error.status)) |> Map.put(:details, [])
     end
   end
 
@@ -47,12 +49,19 @@ defmodule GRPC.RPCError do
     parse_args(t, acc)
   end
 
-  def exception(status, message) when is_atom(status) do
-    %GRPC.RPCError{status: apply(GRPC.Status, status, []), message: message}
+  defp parse_args([{:details, details} | t], acc) do
+    acc = %{acc | details: details}
+    parse_args(t, acc)
+  end
+
+  def exception(status, message, details \\ [])
+
+  def exception(status, message, details) when is_atom(status) do
+    %GRPC.RPCError{status: apply(GRPC.Status, status, []), message: message, details: details}
   end
 
-  def exception(status, message) when is_integer(status) do
-    %GRPC.RPCError{status: status, message: message}
+  def exception(status, message, details) when is_integer(status) do
+    %GRPC.RPCError{status: status, message: message, details: details}
   end
 
   defp status_message(1), do: "The operation was cancelled (typically by the caller)"

diff --git a/lib/grpc/stub.ex b/lib/grpc/stub.ex
@@ -501,7 +501,16 @@ defmodule GRPC.Stub do
     if status == GRPC.Status.ok() do
       :ok
     else
-      {:error, %GRPC.RPCError{status: status, message: trailers["grpc-message"]}}
+      {:error,
+       %GRPC.RPCError{
+         status: status,
+         message: trailers["grpc-message"],
+         # TODO: stop assuming details is a list of strings only
+         details:
+           trailers["grpc-details"]
+           |> String.split(",")
+           |> Enum.filter(fn x -> x != "" end)
+       }}
     end
   end
 

diff --git a/lib/grpc/transport/http2.ex b/lib/grpc/transport/http2.ex
@@ -12,11 +12,13 @@ defmodule GRPC.Transport.HTTP2 do
     %{"content-type" => "application/grpc+#{codec.name}"}
   end
 
-  @spec server_trailers(integer, String.t()) :: map
-  def server_trailers(status \\ Status.ok(), message \\ "") do
+  @spec server_trailers(integer, String.t(), [any()]) :: map
+  def server_trailers(status \\ Status.ok(), message \\ "", details \\ []) do
+    # TODO: stop assuming details is a list of String.t() only
     %{
       "grpc-status" => Integer.to_string(status),
-      "grpc-message" => message
+      "grpc-message" => message,
+      "grpc-details" => details |> Enum.join(",")
     }
   end
 

diff --git a/test/grpc/integration/server_test.exs b/test/grpc/integration/server_test.exs
@@ -88,6 +88,64 @@ defmodule GRPC.Integration.ServerTest do
     end
   end
 
+  defmodule RichErrorErrorServer do
+    use GRPC.Server, service: Helloworld.Greeter.Service
+
+    def say_hello(%{name: "string_errors"}, _stream) do
+      raise GRPC.RPCError,
+        status: GRPC.Status.unauthenticated(),
+        message: "string_errors",
+        details: ["hello", "world"]
+    end
+
+    def say_hello(%{name: "number_errors"}, _stream) do
+      raise GRPC.RPCError,
+        status: GRPC.Status.unauthenticated(),
+        message: "number_errors",
+        details: [1, 2, 3, 4, 5]
+    end
+
+    def say_hello(%{name: "rich_errors"}, _stream) do
+      raise GRPC.RPCError,
+        status: GRPC.Status.unauthenticated(),
+        message: "rich_errors",
+        details: [Helloworld.HelloReply.new(message: "hello world")]
+    end
+  end
+
+  test "error details work" do
+    run_server([RichErrorErrorServer], fn port ->
+      {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
+
+      req = Helloworld.HelloRequest.new(name: "string_errors")
+      {:error, reply} = channel |> Helloworld.Greeter.Stub.say_hello(req)
+
+      assert %GRPC.RPCError{
+               status: GRPC.Status.unauthenticated(),
+               message: "string_errors",
+               details: ["hello", "world"]
+             } == reply
+
+      req = Helloworld.HelloRequest.new(name: "number_errors")
+      {:error, reply} = channel |> Helloworld.Greeter.Stub.say_hello(req)
+
+      assert %GRPC.RPCError{
+               status: GRPC.Status.unauthenticated(),
+               message: "number_errors",
+               details: [1, 2, 3, 4, 5]
+             } == reply
+
+      req = Helloworld.HelloRequest.new(name: "rich_errors")
+      {:error, reply} = channel |> Helloworld.Greeter.Stub.say_hello(req)
+
+      assert %GRPC.RPCError{
+               status: GRPC.Status.unauthenticated(),
+               message: "rich_errors",
+               details: [%Helloworld.HelloReply{message: "hello world"}]
+             } == reply
+    end)
+  end
+
   test "multiple servers works" do
     run_server([FeatureServer, HelloServer], fn port ->
       {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
@@ -109,7 +167,8 @@ defmodule GRPC.Integration.ServerTest do
 
       assert %GRPC.RPCError{
                status: GRPC.Status.unauthenticated(),
-               message: "Please authenticate"
+               message: "Please authenticate",
+               details: []
              } == reply
     end)
   end
@@ -120,7 +179,11 @@ defmodule GRPC.Integration.ServerTest do
       req = Helloworld.HelloRequest.new(name: "unknown error")
 
       assert {:error,
-              %GRPC.RPCError{message: "Internal Server Error", status: GRPC.Status.unknown()}} ==
+              %GRPC.RPCError{
+                message: "Internal Server Error",
+                status: GRPC.Status.unknown(),
+                details: []
+              }} ==
                channel |> Helloworld.Greeter.Stub.say_hello(req)
     end)
   end
@@ -129,7 +192,7 @@ defmodule GRPC.Integration.ServerTest do
     run_server([FeatureErrorServer], fn port ->
       {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
       rect = Routeguide.Rectangle.new()
-      error = %GRPC.RPCError{message: "Please authenticate", status: 16}
+      error = %GRPC.RPCError{message: "Please authenticate", status: 16, details: []}
       assert {:error, ^error} = channel |> Routeguide.RouteGuide.Stub.list_features(rect)
     end)
   end
@@ -148,7 +211,7 @@ defmodule GRPC.Integration.ServerTest do
     run_server([TimeoutServer], fn port ->
       {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
       rect = Routeguide.Rectangle.new()
-      error = %GRPC.RPCError{message: "Deadline expired", status: 4}
+      error = %GRPC.RPCError{message: "Deadline expired", status: 4, details: []}
 
       assert {:error, ^error} =
                channel |> Routeguide.RouteGuide.Stub.list_features(rect, timeout: 500)