[SyncFS] Retry initialization of MetadataDatabase on failure of loading ServiceMetadata

chrome/browser/sync_file_system/drive_backend/metadata_database.cc

 // Copyright 2013 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 "chrome/browser/sync_file_system/drive_backend/metadata_database.h"
 
 #include <algorithm>
 #include <stack>
 
 #include "base/bind.h"
@@ skipping 1410 matching lines @@
   DCHECK(create_param->worker_task_runner->RunsTasksOnCurrentThread());
 
   scoped_ptr<MetadataDatabase> metadata_database(
       new MetadataDatabase(create_param->worker_task_runner,
                            create_param->database_path,
                            create_param->env_override));
   SyncStatusCode status = metadata_database->Initialize();
   if (status != SYNC_STATUS_OK)
     metadata_database.reset();
 
-  metadata_database->DetachFromSequence();
+  if (metadata_database)
+    metadata_database->DetachFromSequence();
   create_param->worker_task_runner->PostTask(
       FROM_HERE,
       base::Bind(
           callback, status, base::Passed(&metadata_database)));
 }
 
 SyncStatusCode MetadataDatabase::Initialize() {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(worker_sequence_checker_.CalledOnValidSequencedThread());
 
@@ skipping 11 matching lines @@
     if (status != SYNC_STATUS_OK)
       return status;
   }
 
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           kEnableMetadataDatabaseOnDisk)) {
     index_ = MetadataDatabaseIndexOnDisk::Create(db_.get());
   } else {
     index_ = MetadataDatabaseIndex::Create(db_.get());
   }
+  if (!index_) {
+    // Delete all entries in |db_| to reset it.
+    scoped_ptr<LevelDBWrapper::Iterator> itr = db_->NewIterator();
+    for (itr->SeekToFirst(); itr->Valid();)
+      itr->Delete();

[nhiroki, 2014/09/02 08:36:25]

Although not related to this CL and you don't have to address now, how about
renaming 'Delete()' to 'DeleteAndAdvance()' or something else? At first I was a
bit confused at this iteration because nobody calls itr->Next()...

[peria, 2014/09/03 04:08:13]

Acknowledged.

+    db_->Commit();

[nhiroki, 2014/09/02 07:26:04]

If you want to delete all records, can you use leveldb::DestroyDB() to avoid a
full scan?

[peria, 2014/09/02 07:36:27]

We have to update LevelDBWrapper class to use it :(
Will do in another patch.

[nhiroki, 2014/09/02 08:36:25]

Okay, can we have a TODO comment about that?

[peria, 2014/09/03 04:08:13]

Done.

+
+    return SYNC_DATABASE_ERROR_FAILED;

[nhiroki, 2014/09/02 07:26:04]

Let me confirm... this makes the SyncFS disabled until reloading the app. Is
this right?

[peria, 2014/09/02 07:36:27]

Yes, it is.
We have to run SyncEngineInitializer again.

[nhiroki, 2014/09/02 08:36:25]

I see... there would be another option to retry the initialization from here
(either is ok to me).

[peria, 2014/09/03 04:08:13]

Acknowledged.

+  }
 
   status = LevelDBStatusToSyncStatusCode(db_->Commit());
   if (status != SYNC_STATUS_OK)
     return status;
 
   UpdateLargestKnownChangeID(index_->GetLargestChangeID());
 
   return status;
 }
 
@@ skipping 481 matching lines @@
       return false;
 
   if (!parents.empty())
     return false;
 
   return true;
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system