Add gRPC API implementationneedlefish

Changes:
- Rename the existing daemon to applaunchd-dbus, and add a new
  version that exposes a gRPC based implementation of the API based
  on the protobuf definition added in a top-level protos directory.
  Having both the D-Bus and gRPC APIs exposed by a single daemon was
  posing difficulties around startup dependencies stemming from D-Bus
  activation of the daemon.  Since the end goal is dropping the D-Bus
  API entirely, it is easier to just add a second daemon for gRPC that
  will eventually be the only one present.
- To facilitate building the two implementations, a significant amount
  of code refactoring has been done to move things from the D-Bus API
  implementing app_launcher.[ch] to systemd_manager.[ch] so the code
  can be reused.
- All use of the systemd D-Bus library except for the path encoding
  helper function has been replaced with GDBus.  The systemd interface
  wrapper code was generated with gdbus-codegen from XML files captured
  via introspection on a running system.  The motivation for this
  change was to avoid multithreading issues with sd_bus exposed when
  calling into it from the gRPC threads.
- The copyright headers in the source files have been tweaked to
  remove the Apache license boilerplate in favour of a SPDX license
  tag.

Notes:
- The gRPC API differs slightly from the D-Bus one in that it has a
  single status streaming RPC method as opposed to the separate signals
  for application started or terminated that the D-Bus API has.
- The gRPC API is currently unauthenticated, the aim is to circle back
  and implement authentication once a consensus can be reached on what
  mechanism should be used (fixed JWT configuration, OAuth, etc.).

Bug-AGL: SPEC-4559

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I828f38a58b60e9959162b98054982124d4fa4380
(cherry picked from commit c52afaf8b5c96136fe20e5d5a1332121d3b09ee9)

1 files changed, 85 insertions, 0 deletions

diff --git a/src/main-grpc.cc b/src/main-grpc.cc
new file mode 100644
index 0000000..d94e4aa
--- /dev/null
+++ b/src/main-grpc.cc
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: Apache-2.0
+/*
+ * Copyright (C) 2022 Konsulko Group
+ */
+
+#include <thread>
+#include <chrono>
+#include <glib.h>
+#include <glib-unix.h>
+
+#include "systemd_manager.h"
+#include "AppLauncherImpl.h"
+
+GMainLoop *main_loop = NULL;
+
+AppLauncherImpl *g_service = NULL;
+
+static gboolean quit_cb(gpointer user_data)
+{
+    g_info("Quitting...");
+
+    if (main_loop)
+        g_idle_add(G_SOURCE_FUNC(g_main_loop_quit), main_loop);
+    else
+        exit(0);
+
+    return G_SOURCE_REMOVE;
+}
+
+void RunGrpcServer(std::shared_ptr<Server> &server)
+{
+    // Start server and wait for shutdown
+    server->Wait();
+}
+
+int main(int argc, char *argv[])
+{
+    main_loop = g_main_loop_new(NULL, FALSE);
+
+    SystemdManager *manager = systemd_manager_get_default();
+
+    grpc::EnableDefaultHealthCheckService(true);
+    grpc::reflection::InitProtoReflectionServerBuilderPlugin();
+    ServerBuilder builder;
+
+    // Listen on the given address without any authentication mechanism (for now)
+    std::string server_address("localhost:50052");
+    builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
+
+    // Register "service" as the instance through which we'll communicate with
+    // clients. In this case it corresponds to a *synchronous* service.
+    AppLauncherImpl *service = new AppLauncherImpl(manager);
+    builder.RegisterService(service);
+
+    // Finally assemble the server.
+    std::shared_ptr<Server> server(builder.BuildAndStart());
+    if (!server) {
+        exit(1);
+    }
+    std::cout << "Server listening on " << server_address << std::endl;
+
+    g_unix_signal_add(SIGTERM, quit_cb, (gpointer) &server);
+    g_unix_signal_add(SIGINT, quit_cb, (gpointer) &server);
+
+    // Start gRPC API server on its own thread
+    std::thread grpc_thread(RunGrpcServer, std::ref(server));
+
+    g_main_loop_run(main_loop);
+
+    // Service implementation may have threads blocked from client streaming
+    // RPCs, make sure those exit.
+    service->Shutdown();
+
+    // Need to set a deadline to avoid blocking on clients doing streaming
+    // RPC reads
+    server->Shutdown(std::chrono::system_clock::now() + std::chrono::milliseconds(500));
+
+    grpc_thread.join();
+
+    g_object_unref(manager);
+
+    g_main_loop_unref(main_loop);
+
+    return 0;
+}