Add Drive.MetadataDBValidityCheckFailureReason UMA histogram

According to the latest data, about 0.02% of DB initialization results in discarding old DB which may contain users' unsynced data.
About 2/3 of these failures are due to errors detected by CheckValidity().

Add UMA histogram to help future developers improve this.

BUG=None

Review URL: https://codereview.chromium.org/445513002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288010 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/chromeos/drive/resource_metadata_storage.cc

@@ -38,6 +38,19 @@ enum DBInitStatus {
   DB_INIT_MAX_VALUE,
 };
 
+// Enum to describe DB validity check failure reason.
+enum CheckValidityFailureReason {
+  CHECK_VALIDITY_FAILURE_INVALID_HEADER,
+  CHECK_VALIDITY_FAILURE_BROKEN_ID_ENTRY,
+  CHECK_VALIDITY_FAILURE_BROKEN_ENTRY,
+  CHECK_VALIDITY_FAILURE_INVALID_LOCAL_ID,
+  CHECK_VALIDITY_FAILURE_INVALID_PARENT_ID,
+  CHECK_VALIDITY_FAILURE_BROKEN_CHILD_MAP,
+  CHECK_VALIDITY_FAILURE_CHILD_ENTRY_COUNT_MISMATCH,
+  CHECK_VALIDITY_FAILURE_ITERATOR_ERROR,
+  CHECK_VALIDITY_FAILURE_MAX_VALUE,
+};
+
 // The name of the DB which stores the metadata.
 const base::FilePath::CharType kResourceMapDBName[] =
     FILE_PATH_LITERAL("resource_metadata_resource_map.db");
@@ -163,6 +176,12 @@ bool MoveIfPossible(const base::FilePath& from, const base::FilePath& to) {
   return !base::PathExists(from) || base::Move(from, to);
 }
 
+void RecordCheckValidityFailure(CheckValidityFailureReason reason) {
+  UMA_HISTOGRAM_ENUMERATION("Drive.MetadataDBValidityCheckFailureReason",
+                            reason,
+                            CHECK_VALIDITY_FAILURE_MAX_VALUE);
+}
+
 }  // namespace
 
 ResourceMetadataStorage::Iterator::Iterator(scoped_ptr<leveldb::Iterator> it)
@@ -932,6 +951,7 @@ bool ResourceMetadataStorage::CheckValidity() {
       !header.ParseFromArray(it->value().data(), it->value().size()) ||
       header.version() != kDBVersion) {
     DLOG(ERROR) << "Invalid header detected. version = " << header.version();
+    RecordCheckValidityFailure(CHECK_VALIDITY_FAILURE_INVALID_HEADER);
     return false;
   }
 
@@ -962,6 +982,7 @@ bool ResourceMetadataStorage::CheckValidity() {
           leveldb::Slice(GetIdEntryKey(entry.resource_id())) == it->key();
       if (!ok) {
         DLOG(ERROR) << "Broken ID entry. status = " << status.ToString();
+        RecordCheckValidityFailure(CHECK_VALIDITY_FAILURE_BROKEN_ID_ENTRY);
         return false;
       }
       continue;
@@ -970,11 +991,13 @@ bool ResourceMetadataStorage::CheckValidity() {
     // Check if stored data is broken.
     if (!entry.ParseFromArray(it->value().data(), it->value().size())) {
       DLOG(ERROR) << "Broken entry detected";
+      RecordCheckValidityFailure(CHECK_VALIDITY_FAILURE_BROKEN_ENTRY);
       return false;
     }
 
     if (leveldb::Slice(entry.local_id()) != it->key()) {
       DLOG(ERROR) << "Wrong local ID.";
+      RecordCheckValidityFailure(CHECK_VALIDITY_FAILURE_INVALID_LOCAL_ID);
       return false;
     }
 
@@ -986,6 +1009,7 @@ bool ResourceMetadataStorage::CheckValidity() {
           &serialized_entry);
       if (!status.ok()) {
         DLOG(ERROR) << "Can't get parent entry. status = " << status.ToString();
+        RecordCheckValidityFailure(CHECK_VALIDITY_FAILURE_INVALID_PARENT_ID);
         return false;
       }
 
@@ -997,14 +1021,22 @@ bool ResourceMetadataStorage::CheckValidity() {
           &child_id);
       if (!status.ok() || leveldb::Slice(child_id) != it->key()) {
         DLOG(ERROR) << "Child map is broken. status = " << status.ToString();
+        RecordCheckValidityFailure(CHECK_VALIDITY_FAILURE_BROKEN_CHILD_MAP);
         return false;
       }
       ++num_entries_with_parent;
     }
   }
-  if (!it->status().ok() || num_child_entries != num_entries_with_parent) {
+  if (!it->status().ok()) {
     DLOG(ERROR) << "Error during checking resource map. status = "
                 << it->status().ToString();
+    RecordCheckValidityFailure(CHECK_VALIDITY_FAILURE_ITERATOR_ERROR);
+    return false;
+  }
+  if (num_child_entries != num_entries_with_parent) {
+    DLOG(ERROR) << "Child entry count mismatch";
+    RecordCheckValidityFailure(
+        CHECK_VALIDITY_FAILURE_CHILD_ENTRY_COUNT_MISMATCH);
     return false;
   }
   return true;

tools/metrics/histograms/histograms.xml

@@ -5490,6 +5490,17 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Drive.MetadataDBValidityCheckFailureReason"
+    enum="DriveMetadataDBValidityCheckFailureReason">
+  <owner>bengold@chromium.org</owner>
+  <owner>hashimoto@chromium.org</owner>
+  <summary>
+    Reason of drive resource metadata database validity check failure. Recorded
+    when the validity check fails during Drive metadata initialization triggered
+    by profile initialization.
+  </summary>
+</histogram>
+
 <histogram name="Drive.MetadataDBVersionBeforeUpgradeCheck">
   <owner>joshwoodward@google.com</owner>
   <summary>
@@ -38211,6 +38222,17 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="9" label="Cannot open existing DB. Created new DB."/>
 </enum>
 
+<enum name="DriveMetadataDBValidityCheckFailureReason" type="int">
+  <int value="0" label="Invalid header"/>
+  <int value="1" label="Broken ID entry"/>
+  <int value="2" label="Broken entry"/>
+  <int value="3" label="Invalid local ID"/>
+  <int value="4" label="Invalid parent ID"/>
+  <int value="5" label="Broken child map"/>
+  <int value="6" label="Child entry count mismatch"/>
+  <int value="7" label="Iterator error"/>
+</enum>
+
 <enum name="EAPInnerProtocol" type="int">
   <int value="0" label="UNKNOWN"/>
   <int value="1" label="NONE"/>