[Sync::USS] Add UMA to track missing bookmark permanent node after merge

Bug: 964341
Change-Id: Id669a728089030cfb7f638eaa38668ac15e2bad1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617442
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661028}

components/sync_bookmarks/bookmark_model_type_processor.cc

@@ -36,6 +36,47 @@ namespace sync_bookmarks {
 
 namespace {
 
+// Metrics: "Sync.MissingBookmarkPermanentNodes"
+// These values are persisted to logs. Entries should not be renumbered and
+// numeric values should never be reused.
+enum class MissingPermanentNodes {
+  kBookmarkBar = 0,
+  kOtherBookmarks = 1,
+  kMobileBookmarks = 2,
+  kBookmarkBarAndOtherBookmarks = 3,
+  kBookmarkBarAndMobileBookmarks = 4,
+  kOtherBookmarksAndMobileBookmarks = 5,
+  kBookmarkBarAndOtherBookmarksAndMobileBookmarks = 6,
+
+  kMaxValue = kBookmarkBarAndOtherBookmarksAndMobileBookmarks,
+};
+
+void LogMissingPermanentNodes(
+    const SyncedBookmarkTracker::Entity* bookmark_bar,
+    const SyncedBookmarkTracker::Entity* other_bookmarks,
+    const SyncedBookmarkTracker::Entity* mobile_bookmarks) {
+  MissingPermanentNodes missing_nodes;
+  if (!bookmark_bar && other_bookmarks && mobile_bookmarks) {
+    missing_nodes = MissingPermanentNodes::kBookmarkBar;
+  } else if (bookmark_bar && !other_bookmarks && mobile_bookmarks) {
+    missing_nodes = MissingPermanentNodes::kOtherBookmarks;
+  } else if (bookmark_bar && other_bookmarks && !mobile_bookmarks) {
+    missing_nodes = MissingPermanentNodes::kMobileBookmarks;
+  } else if (!bookmark_bar && !other_bookmarks && mobile_bookmarks) {
+    missing_nodes = MissingPermanentNodes::kBookmarkBarAndOtherBookmarks;
+  } else if (!bookmark_bar && other_bookmarks && !mobile_bookmarks) {
+    missing_nodes = MissingPermanentNodes::kBookmarkBarAndMobileBookmarks;
+  } else if (bookmark_bar && !other_bookmarks && !mobile_bookmarks) {
+    missing_nodes = MissingPermanentNodes::kOtherBookmarksAndMobileBookmarks;
+  } else {
+    // All must be missing.
+    missing_nodes =
+        MissingPermanentNodes::kBookmarkBarAndOtherBookmarksAndMobileBookmarks;
+  }
+  UMA_HISTOGRAM_ENUMERATION("Sync.MissingBookmarkPermanentNodes",
+                            missing_nodes);
+}
+
 // Enables scheduling bookmark model saving only upon changes in entity sync
 // metadata. This would stop persisting changes to the model type state that
 // doesn't involve changes to the entity metadata as well.
@@ -203,6 +244,12 @@ void BookmarkModelTypeProcessor::OnUpdateReceived(
             bookmark_model_->other_node()) ||
         !bookmark_tracker_->GetEntityForBookmarkNode(
             bookmark_model_->mobile_node())) {
+      LogMissingPermanentNodes(bookmark_tracker_->GetEntityForBookmarkNode(
+                                   bookmark_model_->bookmark_bar_node()),
+                               bookmark_tracker_->GetEntityForBookmarkNode(
+                                   bookmark_model_->other_node()),
+                               bookmark_tracker_->GetEntityForBookmarkNode(
+                                   bookmark_model_->mobile_node()));
       StopTrackingMetadata();
       bookmark_tracker_.reset();
       error_handler_.Run(

tools/metrics/histograms/enums.xml

@@ -54706,6 +54706,16 @@ would be helpful to identify which type is being sent.
   <int value="1" label="Unknown reason"/>
 </enum>
 
+<enum name="SyncMissingBookmarkPermanentNodes">
+  <int value="0" label="Bookmark Bar"/>
+  <int value="1" label="Other Bookmarks"/>
+  <int value="2" label="Mobile Bookmarks"/>
+  <int value="3" label="Bookmark Bar and Other Bookmarks"/>
+  <int value="4" label="Bookmarks Bar and Mobile Bookmarks"/>
+  <int value="5" label="Other Bookmarks and Mobile Bookmarks"/>
+  <int value="6" label="Bookmark Bar and Other Bookmarks and Mobile Bookmarks"/>
+</enum>
+
 <enum name="SyncModelTypes">
   <int value="0" label="Unspecified"/>
   <int value="1" label="Top Level Folder"/>

tools/metrics/histograms/histograms.xml

@@ -126460,6 +126460,18 @@ should be kept until we use this API.  -->
   </summary>
 </histogram>
 
+<histogram name="Sync.MissingBookmarkPermanentNodes"
+    enum="SyncMissingBookmarkPermanentNodes" expires_after="M80">
+  <owner>mamir@chromium.org</owner>
+  <owner>mastiz@chromium.org</owner>
+  <summary>
+    Recorded after applying the first sync merge for Bookmarks in case of merge
+    failure. Merge failure is detected by missing one or more permanent nodes in
+    the merge result. This metric records which permanent nodes are missing.
+    It's recorded only for USS infrastrucre.
+  </summary>
+</histogram>
+
 <histogram base="true" name="Sync.ModelTypeConfigurationTime.Ephemeral"
     units="ms" expires_after="2020-05-01">
   <owner>jkrcal@chromium.org</owner>