Do not create GCM store if it is not needed

google_apis/gcm/engine/gcm_store_impl.cc

 // Copyright 2014 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 "google_apis/gcm/engine/gcm_store_impl.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
@@ skipping 32 matching lines @@
   LOADING_DEVICE_CREDENTIALS_FAILED,
   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,
   LOADING_HEARTBEAT_INTERVALS_FAILED,
   LOADING_INSTANCE_ID_DATA_FAILED,
+  STORE_DOES_NOT_EXIST,
 
   // 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;
 
@@ skipping 115 matching lines @@
 }  // namespace
 
 class GCMStoreImpl::Backend
     : public base::RefCountedThreadSafe<GCMStoreImpl::Backend> {
  public:
   Backend(const base::FilePath& path,
           scoped_refptr<base::SequencedTaskRunner> foreground_runner,
           scoped_ptr<Encryptor> encryptor);
 
   // Blocking implementations of GCMStoreImpl methods.
-  void Load(const LoadCallback& callback);
+  void Load(StoreOpenMode open_mode, const LoadCallback& callback);
   void Close();
   void Destroy(const UpdateCallback& callback);
   void SetDeviceCredentials(uint64 device_android_id,
                             uint64 device_security_token,
                             const UpdateCallback& callback);
   void AddRegistration(const std::string& serialized_key,
                        const std::string& serialized_value,
                        const UpdateCallback& callback);
   void RemoveRegistration(const std::string& serialized_key,
                           const UpdateCallback& callback);
@@ skipping 37 matching lines @@
   void RemoveInstanceIDData(const std::string& app_id,
                             const UpdateCallback& callback);
   void SetValue(const std::string& key,
                 const std::string& value,
                 const UpdateCallback& callback);
 
  private:
   friend class base::RefCountedThreadSafe<Backend>;
   ~Backend();
 
-  LoadStatus OpenStoreAndLoadData(LoadResult* result);
+  LoadStatus OpenStoreAndLoadData(StoreOpenMode open_mode, LoadResult* result);
   bool LoadDeviceCredentials(uint64* android_id, uint64* security_token);
   bool LoadRegistrations(std::map<std::string, std::string>* registrations);
   bool LoadIncomingMessages(std::vector<std::string>* incoming_messages);
   bool LoadOutgoingMessages(OutgoingMessageMap* outgoing_messages);
   bool LoadLastCheckinInfo(base::Time* last_checkin_time,
                            std::set<std::string>* accounts);
   bool LoadGServicesSettings(std::map<std::string, std::string>* settings,
                              std::string* digest);
   bool LoadAccountMappingInfo(AccountMappings* account_mappings);
   bool LoadLastTokenFetchTime(base::Time* last_token_fetch_time);
@@ skipping 11 matching lines @@
     const base::FilePath& path,
     scoped_refptr<base::SequencedTaskRunner> foreground_task_runner,
     scoped_ptr<Encryptor> encryptor)
     : path_(path),
       foreground_task_runner_(foreground_task_runner),
       encryptor_(encryptor.Pass()) {
 }
 
 GCMStoreImpl::Backend::~Backend() {}
 
-LoadStatus GCMStoreImpl::Backend::OpenStoreAndLoadData(LoadResult* result) {
+LoadStatus GCMStoreImpl::Backend::OpenStoreAndLoadData(StoreOpenMode open_mode,
+                                                       LoadResult* result) {
   LoadStatus load_status;
   if (db_.get()) {
     LOG(ERROR) << "Attempting to reload open database.";
     return RELOADING_OPEN_STORE;
   }
 
+  // Checks if the store exists or not. Calling DB::Open with create_if_missing
+  // not set will still create a new directory if the store does not exist.
+  if (open_mode == DO_NOT_CREATE && !base::DirectoryExists(path_)) {
+    DVLOG(2) << "Database " << path_.value() << " does not exist";
+    return STORE_DOES_NOT_EXIST;
+  }
+
   leveldb::Options options;
-  options.create_if_missing = true;
+  options.create_if_missing = open_mode == CREATE_IF_MISSING;
   options.reuse_logs = leveldb_env::kDefaultLogReuseOptionValue;
   leveldb::DB* db;
   leveldb::Status status =
       leveldb::DB::Open(options, path_.AsUTF8Unsafe(), &db);
   if (!status.ok()) {
     LOG(ERROR) << "Failed to open database " << path_.value() << ": "
                << status.ToString();
     return OPENING_STORE_FAILED;
   }
 
@@ skipping 21 matching lines @@
   if (!LoadLastTokenFetchTime(&result->last_token_fetch_time))
     return LOADING_LAST_TOKEN_TIME_FAILED;
   if (!LoadHeartbeatIntervals(&result->heartbeat_intervals))
     return LOADING_HEARTBEAT_INTERVALS_FAILED;
   if (!LoadInstanceIDData(&result->instance_id_data))
     return LOADING_INSTANCE_ID_DATA_FAILED;
 
   return LOADING_SUCCEEDED;
 }
 
-void GCMStoreImpl::Backend::Load(const LoadCallback& callback) {
+void GCMStoreImpl::Backend::Load(StoreOpenMode open_mode,
+                                 const LoadCallback& callback) {
   scoped_ptr<LoadResult> result(new LoadResult());
-  LoadStatus load_status = OpenStoreAndLoadData(result.get());
+  LoadStatus load_status = OpenStoreAndLoadData(open_mode, result.get());
   UMA_HISTOGRAM_ENUMERATION("GCM.LoadStatus", load_status, LOAD_STATUS_COUNT);
   if (load_status != LOADING_SUCCEEDED) {
     result->Reset();
+    result->store_does_not_exist = (load_status == STORE_DOES_NOT_EXIST);
     foreground_task_runner_->PostTask(FROM_HERE,
                                       base::Bind(callback,
                                                  base::Passed(&result)));
     return;
   }
 
   // |result->registrations| contains both GCM registrations and InstanceID
   // tokens. Count them separately.
   int gcm_registration_count = 0;
   int instance_id_token_count = 0;
@@ skipping 805 matching lines @@
     scoped_ptr<Encryptor> encryptor)
     : backend_(new Backend(path,
                            base::ThreadTaskRunnerHandle::Get(),
                            encryptor.Pass())),
       blocking_task_runner_(blocking_task_runner),
       weak_ptr_factory_(this) {
 }
 
 GCMStoreImpl::~GCMStoreImpl() {}
 
-void GCMStoreImpl::Load(const LoadCallback& callback) {
+void GCMStoreImpl::Load(StoreOpenMode open_mode, const LoadCallback& callback) {
   blocking_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&GCMStoreImpl::Backend::Load,
                  backend_,
+                 open_mode,
                  base::Bind(&GCMStoreImpl::LoadContinuation,
                             weak_ptr_factory_.GetWeakPtr(),
                             callback)));
 }
 
 void GCMStoreImpl::Close() {
   weak_ptr_factory_.InvalidateWeakPtrs();
   app_message_counts_.clear();
   blocking_task_runner_->PostTask(
       FROM_HERE,
@@ skipping 283 matching lines @@
            removed_message_counts.begin();
        iter != removed_message_counts.end(); ++iter) {
     DCHECK_NE(app_message_counts_.count(iter->first), 0U);
     app_message_counts_[iter->first] -= iter->second;
     DCHECK_GE(app_message_counts_[iter->first], 0);
   }
   callback.Run(true);
 }
 
 }  // namespace gcm