[cdc_stream] Implement stop-service command (#29)

Implements cdc_stream stop-service. Also fixes an issue in the
BackgroundService implementation where Exit() would deadlock since
server shutdown waits for all RPCs to exit.

cdc_stream/stop_service_command.cc

@@ -0,0 +1,70 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "cdc_stream/stop_service_command.h"
+
+#include "absl/strings/str_format.h"
+#include "cdc_stream/background_service_client.h"
+#include "cdc_stream/session_management_server.h"
+#include "common/log.h"
+#include "grpcpp/channel.h"
+#include "grpcpp/create_channel.h"
+#include "grpcpp/support/channel_arguments.h"
+#include "lyra/lyra.hpp"
+
+namespace cdc_ft {
+
+StopServiceCommand::StopServiceCommand(int* exit_code)
+    : BaseCommand("stop-service", "Stops the streaming service", exit_code) {}
+StopServiceCommand::~StopServiceCommand() = default;
+
+void StopServiceCommand::RegisterCommandLineFlags(lyra::command& cmd) {
+  verbosity_ = 2;
+  cmd.add_argument(lyra::opt(verbosity_, "num")
+                       .name("--verbosity")
+                       .help("Verbosity of the log output, default: " +
+                             std::to_string(verbosity_) +
+                             ".Increase to make logs more verbose."));
+
+  service_port_ = SessionManagementServer::kDefaultServicePort;
+  cmd.add_argument(lyra::opt(service_port_, "port")
+                       .name("--service-port")
+                       .help("Local port to use while connecting to the local "
+                             "asset stream service, default: " +
+                             std::to_string(service_port_)));
+}
+
+absl::Status StopServiceCommand::Run() {
+  LogLevel level = Log::VerbosityToLogLevel(verbosity_);
+  ScopedLog scoped_log(std::make_unique<ConsoleLog>(level));
+
+  std::string client_address = absl::StrFormat("localhost:%u", service_port_);
+  std::shared_ptr<grpc::Channel> channel = grpc::CreateCustomChannel(
+      client_address, grpc::InsecureChannelCredentials(),
+      grpc::ChannelArguments());
+
+  BackgroundServiceClient bg_client(channel);
+  absl::Status status = bg_client.Exit();
+  if (status.ok()) {
+    LOG_INFO("Stopped streaming service");
+  } else if (absl::IsUnavailable(status)) {
+    // Server wasn't running. This doesn't count as an error.
+    LOG_INFO("Streaming service already stopped");
+    return absl::OkStatus();
+  }
+
+  return status;
+}
+
+}  // namespace cdc_ft