Add UMA statistics for tracking session storage database opening failures.

webkit/dom_storage/session_storage_database.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 "webkit/dom_storage/session_storage_database.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/stringprintf.h"
 #include "base/string_number_conversions.h"
 #include "base/utf_string_conversions.h"
 #include "googleurl/src/gurl.h"
 #include "third_party/leveldatabase/src/include/leveldb/db.h"
 #include "third_party/leveldatabase/src/include/leveldb/iterator.h"
 #include "third_party/leveldatabase/src/include/leveldb/status.h"
 #include "third_party/leveldatabase/src/include/leveldb/options.h"
 #include "third_party/leveldatabase/src/include/leveldb/write_batch.h"
 
+namespace {
+

[michaeln, 2013/02/27 00:31:57]

Can you define a constant for histogram name value here too.

[marja, 2013/02/27 08:48:25]

Done. I just #define'd it, because we cannot have a std::string here, that would
create a non-trivial static initializer afaics... const char* would work, but it
seems to be discouraged. Let me know if you'd like something else than a
#define.

[michaeln, 2013/02/27 20:31:48]

I would expect compilers to optimize the multiple uses into one byte sequence in
the binary but its a leap of faith. Elsewhere we do like this...
const char kHttpScheme[] = "http";

+enum SessionStorageUMA {
+  SESSION_STORAGE_UMA_SUCCESS,
+  SESSION_STORAGE_UMA_RECREATED,
+  SESSION_STORAGE_UMA_FAIL,
+  SESSION_STORAGE_UMA_MAX
+};
+
+}  // namespace
+
 // Layout of the database:
 // | key                            | value                              |
 // -----------------------------------------------------------------------
 // | map-1-                         | 2 (refcount, start of map-1-* keys)|
 // | map-1-a                        | b (a = b in map 1)                 |
 // | ...                            |                                    |
 // | namespace-                     | dummy (start of namespace-* keys)  |
 // | namespace-1- (1 = namespace id)| dummy (start of namespace-1-* keys)|
 // | namespace-1-origin1            | 1 (mapid)                          |
 // | namespace-1-origin2            | 2                                  |
@@ skipping 250 matching lines @@
     LOG(WARNING) << "Failed to open leveldb in " << file_path_.value()
                  << ", error: " << s.ToString();
     DCHECK(db == NULL);
 
     // Clear the directory and try again.
     file_util::Delete(file_path_, true);
     s = TryToOpen(&db);
     if (!s.ok()) {
       LOG(WARNING) << "Failed to open leveldb in " << file_path_.value()
                    << ", error: " << s.ToString();
+      UMA_HISTOGRAM_ENUMERATION("SessionStorageDatabase.Open",
+                                SESSION_STORAGE_UMA_FAIL,
+                                SESSION_STORAGE_UMA_MAX);
       DCHECK(db == NULL);
       db_error_ = true;
       return false;
     }
+    UMA_HISTOGRAM_ENUMERATION("SessionStorageDatabase.Open",
+                              SESSION_STORAGE_UMA_RECREATED,
+                              SESSION_STORAGE_UMA_MAX);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION("SessionStorageDatabase.Open",
+                              SESSION_STORAGE_UMA_SUCCESS,
+                              SESSION_STORAGE_UMA_MAX);
   }
   db_.reset(db);
   return true;
 }
 
 leveldb::Status SessionStorageDatabase::TryToOpen(leveldb::DB** db) {
   leveldb::Options options;
   // The directory exists but a valid leveldb database might not exist inside it
   // (e.g., a subset of the needed files might be missing). Handle this
   // situation gracefully by creating the database now.
@@ skipping 338 matching lines @@
 std::string SessionStorageDatabase::MapKey(const std::string& map_id,
                                            const std::string& key) {
   return base::StringPrintf("map-%s-%s", map_id.c_str(), key.c_str());
 }
 
 const char* SessionStorageDatabase::NextMapIdKey() {
   return "next-map-id";
 }
 
 }  // namespace dom_storage