[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 "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
@@ skipping 77 matching lines @@
   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(DOMStorageContextImplTest, PersistentIds);
   friend class base::RefCountedThreadSafe<DOMStorageArea>;
 
+  class RateLimiter {

[cmumford, 2015/02/03 00:45:24]

Why not put the implementation of RateLimiter in the *.cc file? I'm not sure
what the rule here is.

[michaeln, 2015/02/03 19:59:15]

because i wasn't done yet :)

+   public:
+    RateLimiter(size_t desired_rate, base::TimeDelta time_quantum)
+        : rate_(desired_rate),
+          samples_(0),
+          time_quantum_(time_quantum) {
+    DCHECK(desired_rate > 0);

[cmumford, 2015/02/03 00:45:24]

Consider using DCHECK_GT instead of DCHECK(a > b)

[michaeln, 2015/02/03 19:59:15]

Done.

+  }

[cmumford, 2015/02/03 00:45:24]

Indenting looks wrong - Reitveld issue?

+
+    void AddSamples(size_t samples) { samples_ += samples; }
+
+    // Computes the total time needed to process the total samples seen
+    // at the desired rate.
+    base::TimeDelta ComputeTimeNeeded() {

[cmumford, 2015/02/03 00:45:24]

Should this be const?

[michaeln, 2015/02/03 19:59:14]

Done.

+      return base::TimeDelta::FromInternalValue
+          ((samples_ / rate_) * time_quantum_.ToInternalValue());
+    }
+
+    // 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) {

[cmumford, 2015/02/03 00:45:24]

Should be a static method?

[michaeln, 2015/02/03 19:59:15]

can't be, this uses the instance method ComputeTimeNeeded()

[cmumford, 2015/02/04 18:43:54]

Then it can be const right?

+      base::TimeDelta time_needed = ComputeTimeNeeded();
+      if (time_needed > elapsed_time)
+        return time_needed - elapsed_time;
+      return base::TimeDelta();
+    }
+
+   private:
+    double rate_;
+    double samples_;
+    base::TimeDelta time_quantum_;
+  };
+
   struct CommitBatch {
     bool clear_all_first;
     DOMStorageValuesMap changed_values;
+
     CommitBatch();
     ~CommitBatch();
+    size_t GetDataSize();

[cmumford, 2015/02/03 00:45:24]

const method.

[michaeln, 2015/02/03 19:59:14]

Done.

   };
 
   ~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 CommitChanges(const CommitBatch* commit_batch);
   void OnCommitComplete();
+  base::TimeDelta ComputeCommitDelay();

[cmumford, 2015/02/03 00:45:24]

const

[michaeln, 2015/02/03 19:59:14]

Done.

 
   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::Time start_time_;
+  RateLimiter data_rate_limiter_;
+  RateLimiter commit_rate_limiter_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_AREA_H_