Reset the GCM store to recover from it when it is busted

google_apis/gcm/engine/gcm_store_impl.cc

Index: google_apis/gcm/engine/gcm_store_impl.cc
diff --git a/google_apis/gcm/engine/gcm_store_impl.cc b/google_apis/gcm/engine/gcm_store_impl.cc
index cbdfa32834e5fa46dd5c46e1246a76b27135011b..405b2126883d59d5358fed33d709197f1c8d9828 100644
--- a/google_apis/gcm/engine/gcm_store_impl.cc
+++ b/google_apis/gcm/engine/gcm_store_impl.cc
@@ -30,6 +30,28 @@ namespace gcm {
 
 namespace {
 
+// This enum is used in an UMA histogram (GCMLoadStatus enum defined in
+// tools/metrics/histograms/histogram.xml). Hence the entries here shouldn't
+// be deleted or re-ordered and new ones should be added to the end.
+enum LoadStatus {

[Nicolas Zea, 2015/02/10 18:59:46]

Do we really care to differentiate all these different failures? They all imply
directory corruption. I'm not sure what value we get out of this.

[jianli, 2015/02/10 19:45:14]

I think we might need more info on the underlying failures. OPENING_STORE_FAILED
means that the leveldb store fails to open due to corruption or IO error. All
LOADING_***_FAILED are mostly related to parsing error. Since now we
automatically reset the store on error, we might not catch the parsing error
immediately when the client change is made. So I think it will be good to record
the UMA.

+  LOADING_SUCCEEDED,
+  RELOADING_OPEN_STORE,
+  OPENING_STORE_FAILED,
+  LOADING_DEVICE_CREDENTIAL_FAILED,

[fgorski, 2015/02/10 18:31:31]

credentials

[jianli, 2015/02/10 19:45:14]

Done.

+  LOADING_REGISTRATION_FAILED,
+  LOADING_INCOMING_MESSAGES_FAILED,
+  LOADING_OUTGOING_MESSAGES_FAILED,
+  LOADING_LAST_CHECKIN_INFO_FAILED,
+  LOADING_GSERVICE_SETTINGS_FAILED,
+  LOADING_ACCOUNT_MAPPING_FAILED,
+  LOADING_LAST_TOKEN_TIME_FAILED,
+
+  // NOTE: always keep this entry at the end. Add new status types only
+  // immediately above this line. Make sure to update the corresponding
+  // histogram enum accordingly.
+  LOAD_STATUS_COUNT
+};
+
 // Limit to the number of outstanding messages per app.
 const int kMessagesPerAppLimit = 20;
 
@@ -178,6 +200,7 @@ class GCMStoreImpl::Backend
   friend class base::RefCountedThreadSafe<Backend>;
   ~Backend();
 
+  LoadStatus OpenStoreAndLoadData(LoadResult* result);
   bool LoadDeviceCredentials(uint64* android_id, uint64* security_token);
   bool LoadRegistrations(RegistrationInfoMap* registrations);
   bool LoadIncomingMessages(std::vector<std::string>* incoming_messages);
@@ -207,14 +230,11 @@ GCMStoreImpl::Backend::Backend(
 
 GCMStoreImpl::Backend::~Backend() {}
 
-void GCMStoreImpl::Backend::Load(const LoadCallback& callback) {
-  scoped_ptr<LoadResult> result(new LoadResult());
+LoadStatus GCMStoreImpl::Backend::OpenStoreAndLoadData(LoadResult* result) {
+  LoadStatus load_status;
   if (db_.get()) {
     LOG(ERROR) << "Attempting to reload open database.";
-    foreground_task_runner_->PostTask(FROM_HERE,
-                                      base::Bind(callback,
-                                                 base::Passed(&result)));
-    return;
+    return RELOADING_OPEN_STORE;
   }
 
   leveldb::Options options;
@@ -222,28 +242,44 @@ void GCMStoreImpl::Backend::Load(const LoadCallback& callback) {
   leveldb::DB* db;
   leveldb::Status status =
       leveldb::DB::Open(options, path_.AsUTF8Unsafe(), &db);
-  UMA_HISTOGRAM_BOOLEAN("GCM.LoadSucceeded", status.ok());
   if (!status.ok()) {
     LOG(ERROR) << "Failed to open database " << path_.value() << ": "
                << status.ToString();
-    foreground_task_runner_->PostTask(FROM_HERE,
-                                      base::Bind(callback,
-                                                 base::Passed(&result)));
-    return;
+    return OPENING_STORE_FAILED;
   }
-  db_.reset(db);
 
+  db_.reset(db);
   if (!LoadDeviceCredentials(&result->device_android_id,
-                             &result->device_security_token) ||
-      !LoadRegistrations(&result->registrations) ||
-      !LoadIncomingMessages(&result->incoming_messages) ||
-      !LoadOutgoingMessages(&result->outgoing_messages) ||
-      !LoadLastCheckinInfo(&result->last_checkin_time,
-                           &result->last_checkin_accounts) ||
-      !LoadGServicesSettings(&result->gservices_settings,
-                             &result->gservices_digest) ||
-      !LoadAccountMappingInfo(&result->account_mappings) ||
-      !LoadLastTokenFetchTime(&result->last_token_fetch_time)) {
+                             &result->device_security_token)) {
+    return LOADING_DEVICE_CREDENTIAL_FAILED;
+  }
+  if (!LoadRegistrations(&result->registrations))
+    return LOADING_REGISTRATION_FAILED;
+  if (!LoadIncomingMessages(&result->incoming_messages))
+    return LOADING_INCOMING_MESSAGES_FAILED;
+  if (!LoadOutgoingMessages(&result->outgoing_messages))
+    return LOADING_OUTGOING_MESSAGES_FAILED;
+  if (!LoadLastCheckinInfo(&result->last_checkin_time,
+                           &result->last_checkin_accounts)) {
+    return LOADING_LAST_CHECKIN_INFO_FAILED;
+  }
+  if (!LoadGServicesSettings(&result->gservices_settings,
+                             &result->gservices_digest)) {
+    return load_status = LOADING_GSERVICE_SETTINGS_FAILED;
+  }
+  if (!LoadAccountMappingInfo(&result->account_mappings))
+    return LOADING_ACCOUNT_MAPPING_FAILED;
+  if (!LoadLastTokenFetchTime(&result->last_token_fetch_time))
+     return LOADING_LAST_TOKEN_TIME_FAILED;
+
+  return LOADING_SUCCEEDED;
+}
+
+void GCMStoreImpl::Backend::Load(const LoadCallback& callback) {
+  scoped_ptr<LoadResult> result(new LoadResult());
+  LoadStatus load_status = OpenStoreAndLoadData(result.get());
+  if (load_status != LOADING_SUCCEEDED) {
+    UMA_HISTOGRAM_ENUMERATION("GCM.LoadStatus", load_status, LOAD_STATUS_COUNT);
     result->Reset();
     foreground_task_runner_->PostTask(FROM_HERE,
                                       base::Bind(callback,