UMA counts for corrupt cache db.

chrome/browser/chromeos/gdata/drive_cache_metadata.cc

 // Copyright (c) 2012 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/chromeos/gdata/drive_cache_metadata.h"
 
 #include <leveldb/db.h>
 
 #include "base/callback.h"
 #include "base/file_util.h"
+#include "base/metrics/histogram.h"
 #include "base/sequenced_task_runner.h"
 #include "chrome/browser/chromeos/gdata/drive.pb.h"
 #include "chrome/browser/chromeos/gdata/drive_file_system_util.h"
 
 namespace gdata {
 
 namespace {
 
 // A map table of resource ID to file path.
 typedef std::map<std::string, FilePath> ResourceIdToFilePathMap;
@@ skipping 440 matching lines @@
   leveldb::DB* level_db = NULL;
   leveldb::Options options;
   options.create_if_missing = true;
   leveldb::Status db_status = leveldb::DB::Open(options, db_path.value(),
                                                 &level_db);
 
   // Delete the db and scan the physical cache. This will fix a corrupt db, but
   // perhaps not other causes of failed DB::Open.
   if (!db_status.ok()) {
     DVLOG(1) << "Detected corrupt db";
+    UMA_HISTOGRAM_COUNTS("Drive.CorruptCacheDB", 1);

[satorux1, 2012/09/25 22:40:50]

I think we want to know success/failure ratio and failure reasons, so we want to
do something like:

enum {
  LOAD_SUCCESS,
  LOAD_FAILURE_CORRUPT_DB,
  LOAD_FAILURE_OTHER,
  LOAD_MAX_VALUE,
};

Then do:

UMA_HISTOGRAM_ENUMERATION("Drive.CacheMetadataLoading", LOAD_SUCCESS,
LOAD_MAX_VALUE)

I think we want to distinguish corruption from other errors, so I'd suggest
doing:

if (!db_status.ok()) {
  if (db_status.IsCorruption()) {
    LOG(WARNING) << "Detected corrupt db";
    UMA_HISTOGRAM_ENUMERATION("Drive.CacheMetadataLoading",
LOAD_FAILURE_CORRUPT_DB, LOAD_MAX_VALUE);
  } else {
    LOG(WARNING)  << "Failed to open db for unknown reason";
    UMA_HISTOGRAM_ENUMERATION("Drive.CacheMetadataLoading", LOAD_FAILURE_OTHER,
LOAD_MAX_VALUE);
  }

     const bool deleted = file_util::Delete(db_path, true);
     DCHECK(deleted);
     db_status = leveldb::DB::Open(options, db_path.value(), &level_db);
     // TODO(satorux): Handle the situation where DB::Open fails because of lack
     // of disk space, permissions, or other causes. crbug.com/150840.
     CHECK(db_status.ok());  // Must succeed or we'll crash later.
     scan_cache = true;
   }
   DCHECK(level_db);
   level_db_.reset(level_db);
@@ skipping 131 matching lines @@
   return scoped_ptr<DriveCacheMetadata>(
       new FakeDriveCacheMetadata(blocking_task_runner));
 }
 
 void DriveCacheMetadata::AssertOnSequencedWorkerPool() {
   DCHECK(!blocking_task_runner_ ||
          blocking_task_runner_->RunsTasksOnCurrentThread());
 }
 
 }  // namespace gdata