[DOMStorage] Rate limiting writes to disk.

content/browser/dom_storage/dom_storage_area.h

 // 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.
 
 #ifndef CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_AREA_H_
 #define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_AREA_H_
 
+#include <string>
+
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/nullable_string16.h"
 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
 #include "content/common/dom_storage/dom_storage_types.h"
 #include "url/gurl.h"
 
@@ skipping 40 matching lines @@
                base::NullableString16* old_value);
   bool RemoveItem(const base::string16& key, base::string16* old_value);
   bool Clear();
   void FastClear();
 
   DOMStorageArea* ShallowCopy(
       int64 destination_namespace_id,
       const std::string& destination_persistent_namespace_id);
 
   bool HasUncommittedChanges() const;
+  void ScheduleImmediateCommit();
 
   // Similar to Clear() but more optimized for just deleting
   // without raising events.
   void DeleteOrigin();
 
   // Frees up memory when possible. Typically, this method returns
   // the object to its just constructed state, however if uncommitted
   // changes are pending, it does nothing.
   void PurgeMemory();
 
   // Schedules the commit of any unsaved changes and enters a
   // shutdown state such that the value getters and setters will
   // no longer do anything.
   void Shutdown();
 
   // Returns true if the data is loaded in memory.
   bool IsLoadedInMemory() const { return is_initial_import_done_; }
 
  private:
   friend class DOMStorageAreaTest;
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, DOMStorageAreaBasics);
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, BackingDatabaseOpened);
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, TestDatabaseFilePath);
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, CommitTasks);
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, CommitChangesAtShutdown);
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, DeleteOrigin);
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, PurgeMemory);
+  FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, RateLimiter);
   FRIEND_TEST_ALL_PREFIXES(DOMStorageContextImplTest, PersistentIds);
   friend class base::RefCountedThreadSafe<DOMStorageArea>;
 
+  // Used to rate limit commits.
+  class CONTENT_EXPORT RateLimiter {
+   public:
+    RateLimiter(size_t desired_rate, base::TimeDelta time_quantum);
+
+    void add_samples(size_t samples) {
+      samples_ += samples;
+    }
+
+    // Computes the total time needed to process the total samples seen
+    // at the desired rate.
+    base::TimeDelta ComputeTimeNeeded() const;
+
+    // Given the elapsed time since the start of the rate limiting session,
+    // computes the delay needed to mimic having processed the total samples
+    // seen at the desired rate.
+    base::TimeDelta ComputeDelayNeeded(
+        const base::TimeDelta elapsed_time) const;
+
+   private:
+    float rate_;
+    float samples_;
+    base::TimeDelta time_quantum_;
+  };
+
   struct CommitBatch {
     bool clear_all_first;
     DOMStorageValuesMap changed_values;
+
     CommitBatch();
     ~CommitBatch();
+    size_t GetDataSize() const;
   };
 
   ~DOMStorageArea();
 
   // If we haven't done so already and this is a local storage area,
   // will attempt to read any values for this origin currently
   // stored on disk.
   void InitialImportIfNeeded();
 
   // Post tasks to defer writing a batch of changed values to
   // disk on the commit sequence, and to call back on the primary
   // task sequence when complete.
   CommitBatch* CreateCommitBatchIfNeeded();
   void OnCommitTimer();
+  void PostCommitTask();
   void CommitChanges(const CommitBatch* commit_batch);
   void OnCommitComplete();
+  base::TimeDelta ComputeCommitDelay() const;
 
   void ShutdownInCommitSequence();
 
   int64 namespace_id_;
   std::string persistent_namespace_id_;
   GURL origin_;
   base::FilePath directory_;
   scoped_refptr<DOMStorageTaskRunner> task_runner_;
   scoped_refptr<DOMStorageMap> map_;
   scoped_ptr<DOMStorageDatabaseAdapter> backing_;
   scoped_refptr<SessionStorageDatabase> session_storage_backing_;
   bool is_initial_import_done_;
   bool is_shutdown_;
   scoped_ptr<CommitBatch> commit_batch_;
   int commit_batches_in_flight_;
+  base::TimeTicks start_time_;
+  RateLimiter data_rate_limiter_;
+  RateLimiter commit_rate_limiter_;
+
+  DISALLOW_COPY_AND_ASSIGN(DOMStorageArea);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_AREA_H_