Add traced-process support to external_mojo processes.

To support tracing, a tracing service must also be registered with
the mojo broker.

This change does not implement start-up tracing which may be addressed
at a later time.

If (GN arg) enable_external_mojo_tracing=false (default), then a no-op
tracing client implementation will be used.

Bug: internal b/153566474
Test: Tested tracing with an external tracing service.
Change-Id: I56ccecde888778a3f9a54353bb3e6744fb8194c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2200081Reviewed-by: Alex Sakhartchouk <alexst@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Chris Letnick <cletnick@google.com>
Cr-Commit-Position: refs/heads/master@{#770734}

chromecast/chromecast.gni

@@ -116,6 +116,10 @@ declare_args() {
   # within cast_shell.
   enable_external_mojo_services = is_linux
 
+  # Support Perfetto tracing of processes that depend on entry points in
+  # //chromecast/external_mojo/external_service_support
+  enable_external_mojo_tracing = false
+
   # Recording happens at this sample rate. Must be 16000, 48000 or 96000 Hz.
   audio_input_sample_rate = 16000
 

chromecast/external_mojo/external_service_support/BUILD.gn

@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//chromecast/chromecast.gni")
+
 source_set("external_service") {
   sources = [
     "external_connector.h",
@@ -43,20 +45,72 @@ source_set("process_setup") {
   }
 }
 
+source_set("tracing_client_hdr") {
+  sources = [
+    "tracing_client.h",
+  ]
+}
+
+source_set("tracing_client_dummy") {
+  sources = [
+    "tracing_client_dummy.cc",
+    "tracing_client_dummy.h",
+  ]
+  deps = [
+    ":tracing_client_hdr",
+  ]
+}
+
+source_set("tracing_client_impl") {
+  sources = [
+    "tracing_client_impl.cc",
+    "tracing_client_impl.h",
+  ]
+  deps = [
+    ":external_service",
+    ":tracing_client_hdr",
+    "//base",
+    "//chromecast:chromecast_buildflags",
+    "//mojo/public/cpp/bindings",
+    "//services/tracing:lib",
+    "//services/tracing/public/cpp",
+    "//services/tracing/public/cpp:traced_process",
+    "//services/tracing/public/mojom",
+  ]
+}
+
+group("tracing_client") {
+  public_deps = [
+    ":tracing_client_hdr",
+  ]
+  if (enable_external_mojo_tracing) {
+    public_deps += [ ":tracing_client_impl" ]
+  } else {
+    public_deps += [ ":tracing_client_dummy" ]
+  }
+}
+
 source_set("service_process") {
-  sources = [ "service_process.h" ]
+  sources = [
+    "service_process.h",
+  ]
 }
 
 source_set("standalone_service_main") {
-  sources = [ "standalone_service_main.cc" ]
+  sources = [
+    "standalone_service_main.cc",
+  ]
   deps = [
     ":external_service",
     ":process_setup",
+    ":tracing_client",
     "//base",
     "//chromecast/external_mojo/public/cpp:common",
     "//mojo/core/embedder",
   ]
-  public_deps = [ ":service_process" ]
+  public_deps = [
+    ":service_process",
+  ]
 }
 
 source_set("chromium_service") {
@@ -75,9 +129,13 @@ source_set("chromium_service") {
 }
 
 executable("standalone_mojo_broker") {
-  sources = [ "standalone_mojo_broker.cc" ]
+  sources = [
+    "standalone_mojo_broker.cc",
+  ]
   deps = [
+    ":external_service",
     ":process_setup",
+    ":tracing_client",
     "//base",
     "//chromecast/external_mojo/public/cpp:common",
     "//chromecast/external_mojo/public/cpp:external_mojo_broker",

chromecast/external_mojo/external_service_support/DEPS

@@ -2,4 +2,6 @@ include_rules = [
   "+chromecast/crash",
   "+components/crash/core/app",
   "+mojo/core/embedder",
+  "+services/tracing",
+  "+third_party/perfetto/include/perfetto",
 ]

chromecast/external_mojo/external_service_support/standalone_mojo_broker.cc

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -10,7 +11,10 @@
 #include "base/message_loop/message_pump_type.h"
 #include "base/run_loop.h"
 #include "base/task/single_thread_task_executor.h"
+#include "base/task/thread_pool/thread_pool_instance.h"
+#include "chromecast/external_mojo/external_service_support/external_connector_impl.h"
 #include "chromecast/external_mojo/external_service_support/process_setup.h"
+#include "chromecast/external_mojo/external_service_support/tracing_client.h"
 #include "chromecast/external_mojo/public/cpp/common.h"
 #include "chromecast/external_mojo/public/cpp/external_mojo_broker.h"
 #include "mojo/core/embedder/embedder.h"
@@ -33,10 +37,20 @@ int main(int argc, char** argv) {
       io_task_executor.task_runner(),
       mojo::core::ScopedIPCSupport::ShutdownPolicy::CLEAN);
 
+  base::ThreadPoolInstance::CreateAndStartWithDefaultParams(
+      "StandaloneMojoBroker");
+
   chromecast::external_mojo::ExternalMojoBroker broker(
       chromecast::external_mojo::GetBrokerPath());
 
+  chromecast::external_service_support::ExternalConnectorImpl tracing_connector(
+      chromecast::external_mojo::GetBrokerPath(), broker.CreateConnector());
+  auto tracing_client =
+      chromecast::external_service_support::TracingClient::Create(
+          &tracing_connector);
+
   run_loop.Run();
+  base::ThreadPoolInstance::Get()->Shutdown();
 
   return 0;
 }

chromecast/external_mojo/external_service_support/standalone_service_main.cc

@@ -15,6 +15,7 @@
 #include "chromecast/external_mojo/external_service_support/external_connector.h"
 #include "chromecast/external_mojo/external_service_support/process_setup.h"
 #include "chromecast/external_mojo/external_service_support/service_process.h"
+#include "chromecast/external_mojo/external_service_support/tracing_client.h"
 #include "chromecast/external_mojo/public/cpp/common.h"
 #include "mojo/core/embedder/embedder.h"
 #include "mojo/core/embedder/scoped_ipc_support.h"
@@ -26,6 +27,8 @@ struct GlobalState {
       service_process;
   std::unique_ptr<chromecast::external_service_support::ExternalConnector>
       connector;
+  std::unique_ptr<chromecast::external_service_support::TracingClient>
+      tracing_client;
 };
 
 void OnConnected(
@@ -33,6 +36,9 @@ void OnConnected(
     std::unique_ptr<chromecast::external_service_support::ExternalConnector>
         connector) {
   state->connector = std::move(connector);
+  state->tracing_client =
+      chromecast::external_service_support::TracingClient::Create(
+          state->connector.get());
   state->service_process =
       chromecast::external_service_support::ServiceProcess::Create(
           state->connector.get());

chromecast/external_mojo/external_service_support/tracing_client.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#ifndef CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_H_
+#define CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_H_
+
+#include <memory>
+#include <string>
+
+namespace chromecast {
+namespace external_service_support {
+class ExternalConnector;
+
+// TracingClient Supports the tracing of processes that connect to a central
+// tracing service through an ExternalConnector.
+class TracingClient {
+ public:
+  TracingClient() = default;
+  virtual ~TracingClient() = default;
+
+  static const char kTracingServiceName[];
+
+  static std::unique_ptr<TracingClient> Create(ExternalConnector* connector);
+
+ private:
+  TracingClient(const TracingClient&) = delete;
+  TracingClient& operator=(const TracingClient&) = delete;
+};
+
+}  // namespace external_service_support
+}  // namespace chromecast
+
+#endif  // CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_H_

chromecast/external_mojo/external_service_support/tracing_client_dummy.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#include "chromecast/external_mojo/external_service_support/tracing_client_dummy.h"
+
+namespace chromecast {
+namespace external_service_support {
+
+// static
+const char TracingClient::kTracingServiceName[] = "unknown";
+
+// static
+std::unique_ptr<TracingClient> TracingClient::Create(
+    ExternalConnector* connector) {
+  return std::make_unique<TracingClientDummy>();
+}
+
+}  // namespace external_service_support
+}  // namespace chromecast

chromecast/external_mojo/external_service_support/tracing_client_dummy.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#ifndef CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_DUMMY_H_
+#define CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_DUMMY_H_
+
+#include "chromecast/external_mojo/external_service_support/tracing_client.h"
+
+namespace chromecast {
+namespace external_service_support {
+
+// Dummy implementation for build configurations that do not enable tracing.
+class TracingClientDummy : public TracingClient {
+ public:
+  TracingClientDummy() = default;
+  ~TracingClientDummy() override = default;
+
+ private:
+  TracingClientDummy(const TracingClientDummy&) = delete;
+  TracingClientDummy& operator=(const TracingClientDummy&) = delete;
+};
+
+}  // namespace external_service_support
+}  // namespace chromecast
+
+#endif  // CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_DUMMY_H_

chromecast/external_mojo/external_service_support/tracing_client_impl.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#include "chromecast/external_mojo/external_service_support/tracing_client_impl.h"
+
+#include "base/command_line.h"
+#include "base/process/process.h"
+#include "base/trace_event/trace_event.h"
+#include "chromecast/external_mojo/external_service_support/external_connector.h"
+#include "mojo/public/cpp/bindings/pending_receiver.h"
+#include "services/tracing/public/cpp/trace_startup.h"
+#include "services/tracing/public/cpp/traced_process.h"
+#include "services/tracing/public/mojom/traced_process.mojom.h"
+
+namespace chromecast {
+namespace external_service_support {
+
+// static
+const char TracingClient::kTracingServiceName[] = "external_tracing";
+
+// static
+std::unique_ptr<TracingClient> TracingClient::Create(
+    ExternalConnector* connector) {
+  return std::make_unique<TracingClientImpl>(connector);
+}
+
+TracingClientImpl::TracingClientImpl(ExternalConnector* connector)
+    : connector_(connector) {
+  DCHECK(connector_);
+
+  // Setup this process.
+  base::trace_event::TraceLog::GetInstance()->set_process_name(
+      base::CommandLine::ForCurrentProcess()->GetProgram().value());
+  // TODO(cletnick): Support initializing startup tracing without
+  // depending on per-process command-line arguments.
+  tracing::EnableStartupTracingIfNeeded();
+  tracing::InitTracingPostThreadPoolStartAndFeatureList();
+
+  // Connect to service.
+  connector_->BindInterface(TracingClient::kTracingServiceName,
+                            tracing_service_.BindNewPipeAndPassReceiver());
+  // base::Unretained(this) is safe here because the mojo::Remote
+  // |tracing_service_| is owned by |this| and will not run the registered
+  // callback after destruction.
+  tracing_service_.set_disconnect_handler(base::BindOnce(
+      &TracingClientImpl::TracingServiceDisconnected, base::Unretained(this)));
+
+  // Register with service.
+  mojo::PendingRemote<tracing::mojom::TracedProcess> remote_process;
+  tracing::TracedProcess::OnTracedProcessRequest(
+      remote_process.InitWithNewPipeAndPassReceiver());
+  tracing_service_->AddClient(tracing::mojom::ClientInfo::New(
+      base::Process::Current().Pid(), std::move(remote_process)));
+}
+
+TracingClientImpl::~TracingClientImpl() = default;
+
+void TracingClientImpl::TracingServiceDisconnected() {
+  tracing_service_.reset();
+  tracing::TracedProcess::ResetTracedProcessReceiver();
+  LOG(ERROR) << "Disconnected from tracing service. Not reconnecting.";
+}
+
+}  // namespace external_service_support
+}  // namespace chromecast

chromecast/external_mojo/external_service_support/tracing_client_impl.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#ifndef CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_IMPL_H_
+#define CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_IMPL_H_
+
+#include "chromecast/external_mojo/external_service_support/tracing_client.h"
+#include "mojo/public/cpp/bindings/remote.h"
+#include "services/tracing/public/mojom/tracing_service.mojom.h"
+
+namespace chromecast {
+namespace external_service_support {
+class ExternalConnector;
+
+// TracingClient implementation for connecting to a tracing::TracingService
+// instance through an external mojo broker.
+class TracingClientImpl : public TracingClient {
+ public:
+  explicit TracingClientImpl(ExternalConnector* connector);
+  ~TracingClientImpl() override;
+
+ private:
+  void TracingServiceDisconnected();
+
+  mojo::Remote<tracing::mojom::TracingService> tracing_service_;
+
+  ExternalConnector* const connector_;
+
+  TracingClientImpl(const TracingClientImpl&) = delete;
+  TracingClientImpl& operator=(const TracingClientImpl&) = delete;
+};
+
+}  // namespace external_service_support
+}  // namespace chromecast
+
+#endif  // CHROMECAST_EXTERNAL_MOJO_EXTERNAL_SERVICE_SUPPORT_TRACING_CLIENT_IMPL_H_

chromecast/external_mojo/public/cpp/external_mojo_broker.cc

@@ -20,6 +20,7 @@
 #include "base/message_loop/message_pump_for_io.h"
 #include "base/optional.h"
 #include "base/token.h"
+#include "base/trace_event/trace_event.h"
 #include "chromecast/external_mojo/public/cpp/common.h"
 #include "chromecast/external_mojo/public/mojom/connector.mojom.h"
 #include "mojo/public/cpp/bindings/pending_receiver.h"
@@ -223,6 +224,8 @@ class ExternalMojoBroker::ConnectorImpl : public mojom::ExternalConnector {
       LOG(ERROR) << "Duplicate service " << service_name;
       return;
     }
+    TRACE_EVENT_INSTANT1("mojom", "RegisterService", TRACE_EVENT_SCOPE_THREAD,
+                         "service", service_name);
     LOG(INFO) << "Register service " << service_name;
     mojo::Remote<mojom::ExternalService> service(std::move(service_remote));
     service.set_disconnect_handler(base::BindOnce(
@@ -248,6 +251,8 @@ class ExternalMojoBroker::ConnectorImpl : public mojom::ExternalConnector {
                      const std::string& interface_name,
                      mojo::ScopedMessagePipeHandle interface_pipe) override {
     LOG(INFO) << "Request for " << service_name << ":" << interface_name;
+    TRACE_EVENT_INSTANT1("mojom", "BindToService", TRACE_EVENT_SCOPE_THREAD,
+                         "service", service_name);
     auto it = services_.find(service_name);
     if (it != services_.end()) {
       LOG(INFO) << "Found externally-registered " << service_name;
@@ -322,6 +327,8 @@ class ExternalMojoBroker::ConnectorImpl : public mojom::ExternalConnector {
 
   void OnServiceLost(const std::string& service_name) {
     LOG(INFO) << service_name << " disconnected";
+    TRACE_EVENT_INSTANT1("mojom", "ServiceDisconnected",
+                         TRACE_EVENT_SCOPE_THREAD, "service", service_name);
     services_.erase(service_name);
     services_info_[service_name].disconnect_time = base::TimeTicks::Now();
   }