Metrics for PluginVM DLC rollout

Measure the rate in which PluginVM DLC is fallingback to rootfs resident
PluginVM. A good metric to have in order to determine a stable state of
DLC(s) to deem removal from rootfs in the future.

Bug: chromium:145814572
Test: unit_tests --gtest_filter=PluginVm*
Change-Id: Ib13aa2f6922954bc18f973abf746a3485d0980fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2004056
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Timothy Loh <timloh@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732536}

chrome/browser/chromeos/plugin_vm/plugin_vm_installer.cc

@@ -169,6 +169,8 @@ void PluginVmInstaller::OnDlcDownloadCompleted(
     state_ = State::DOWNLOAD_DLC_FAILED;
     if (observer_)
       observer_->OnDownloadFailed(FailureReason::DLC_DOWNLOAD_FAILED);
+    RecordPluginVmDlcUseResultHistogram(
+        PluginVmDlcUseResult::kFallbackToRootFsInvalidDlcError);
     return;
   }
 
@@ -178,6 +180,10 @@ void PluginVmInstaller::OnDlcDownloadCompleted(
     // PluginVM will be rootfs resident as a fallback.
     LOG(ERROR) << "PluginVM DLC installation failed, falling back to rootfs "
                   "resident PluginVM.";
+    RecordPluginVmDlcUseResultHistogram(
+        PluginVmDlcUseResult::kFallbackToRootFsInternalDlcError);
+  } else {
+    RecordPluginVmDlcUseResultHistogram(PluginVmDlcUseResult::kDlcSuccess);
   }
 
   if (observer_)

chrome/browser/chromeos/plugin_vm/plugin_vm_installer_unittest.cc

@@ -300,11 +300,11 @@ class PluginVmInstallerDownloadServiceTest : public PluginVmInstallerTestBase {
   }
 
   void TearDown() override {
-    PluginVmInstallerTestBase::TearDown();
-
     histogram_tester_.reset();
     download_service_.reset();
     client_.reset();
+
+    PluginVmInstallerTestBase::TearDown();
   }
 
   std::unique_ptr<download::test::TestDownloadService> download_service_;
@@ -353,6 +353,13 @@ class PluginVmInstallerDriveTest : public PluginVmInstallerTestBase {
 
     installer_->SetDriveDownloadServiceForTesting(
         std::move(drive_download_service));
+    histogram_tester_ = std::make_unique<base::HistogramTester>();
+  }
+
+  void TearDown() override {
+    histogram_tester_.reset();
+
+    PluginVmInstallerTestBase::TearDown();
   }
 
   SimpleFakeDriveService* SetUpSimpleFakeDriveService() {
@@ -367,6 +374,7 @@ class PluginVmInstallerDriveTest : public PluginVmInstallerTestBase {
 
   PluginVmDriveImageDownloadService* drive_download_service_;
   drive::FakeDriveService* fake_drive_service_;
+  std::unique_ptr<base::HistogramTester> histogram_tester_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PluginVmInstallerDriveTest);
@@ -619,6 +627,8 @@ TEST_F(PluginVmInstallerDriveTest, SuccessfulDriveDownloadTest) {
       .Times(AtLeast(1));
 
   StartAndRunToCompletion();
+  histogram_tester_->ExpectUniqueSample(kPluginVmDlcUseResultHistogram,
+                                        PluginVmDlcUseResult::kDlcSuccess, 1);
 }
 
 // TODO(b/145814572): Modify test to block once PluginVM DLC is stable and
@@ -632,6 +642,9 @@ TEST_F(PluginVmInstallerDriveTest,
   EXPECT_CALL(*observer_, OnDownloadCompleted());
 
   StartAndRunToCompletion();
+  histogram_tester_->ExpectUniqueSample(
+      kPluginVmDlcUseResultHistogram,
+      PluginVmDlcUseResult::kFallbackToRootFsInternalDlcError, 1);
 }
 
 TEST_F(PluginVmInstallerDriveTest, InstallingPluginVmDlcWhenUnsupported) {
@@ -642,6 +655,9 @@ TEST_F(PluginVmInstallerDriveTest, InstallingPluginVmDlcWhenUnsupported) {
   EXPECT_CALL(*observer_, OnDownloadFailed(_)).Times(1);
 
   StartAndRunToCompletion();
+  histogram_tester_->ExpectUniqueSample(
+      kPluginVmDlcUseResultHistogram,
+      PluginVmDlcUseResult::kFallbackToRootFsInvalidDlcError, 1);
 }
 
 }  // namespace plugin_vm

chrome/browser/chromeos/plugin_vm/plugin_vm_metrics_util.cc

@@ -10,6 +10,7 @@ const char kPluginVmImageDownloadedSizeHistogram[] =
     "PluginVm.Image.DownloadedSize";
 const char kPluginVmLaunchResultHistogram[] = "PluginVm.LaunchResult";
 const char kPluginVmSetupResultHistogram[] = "PluginVm.SetupResult";
+const char kPluginVmDlcUseResultHistogram[] = "PluginVm.DlcUseResult";
 const char kPluginVmSetupTimeHistogram[] = "PluginVm.SetupTime";
 
 void RecordPluginVmImageDownloadedSizeHistogram(uint64_t bytes_downloaded) {
@@ -26,6 +27,10 @@ void RecordPluginVmSetupResultHistogram(PluginVmSetupResult setup_result) {
   base::UmaHistogramEnumeration(kPluginVmSetupResultHistogram, setup_result);
 }
 
+void RecordPluginVmDlcUseResultHistogram(PluginVmDlcUseResult dlc_use_result) {
+  base::UmaHistogramEnumeration(kPluginVmDlcUseResultHistogram, dlc_use_result);
+}
+
 void RecordPluginVmSetupTimeHistogram(base::TimeDelta setup_time) {
   base::UmaHistogramLongTimes(kPluginVmSetupTimeHistogram, setup_time);
 }

chrome/browser/chromeos/plugin_vm/plugin_vm_metrics_util.h

@@ -12,6 +12,7 @@ namespace plugin_vm {
 extern const char kPluginVmImageDownloadedSizeHistogram[];
 extern const char kPluginVmLaunchResultHistogram[];
 extern const char kPluginVmSetupResultHistogram[];
+extern const char kPluginVmDlcUseResultHistogram[];
 // Histogram for recording successful setup time.
 // When error occurs and user hits retry button in setup dialog - time between
 // pressing retry button and setup being finished is recorded.
@@ -46,9 +47,17 @@ enum class PluginVmSetupResult {
   kMaxValue = kUserCancelledDownloadingPluginVmDlc,
 };
 
+enum class PluginVmDlcUseResult {
+  kDlcSuccess = 0,
+  kFallbackToRootFsInvalidDlcError = 1,
+  kFallbackToRootFsInternalDlcError = 2,
+  kMaxValue = kFallbackToRootFsInternalDlcError,
+};
+
 void RecordPluginVmImageDownloadedSizeHistogram(uint64_t bytes_downloaded);
 void RecordPluginVmLaunchResultHistogram(PluginVmLaunchResult launch_result);
 void RecordPluginVmSetupResultHistogram(PluginVmSetupResult setup_result);
+void RecordPluginVmDlcUseResultHistogram(PluginVmDlcUseResult dlc_use_result);
 void RecordPluginVmSetupTimeHistogram(base::TimeDelta setup_time);
 
 }  // namespace plugin_vm