[Offline Pages] Two-step expiration in storage manager.

components/offline_pages/offline_page_storage_manager.h

 // Copyright 2016 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 COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_STORAGE_MANAGER_H_
 #define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_STORAGE_MANAGER_H_
 
 #include <stdint.h>
 
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "components/offline_pages/archive_manager.h"
 #include "components/offline_pages/offline_page_types.h"
 
 namespace base {
 class Clock;
 }  // namespace base
 
 namespace offline_pages {
 
 // Limit of the total storage space occupied by offline pages should be 30% of
 // available storage. And we clear storage when it is over the threshold,
-// reducing the usage below threshold.
+// reducing the usage below the 10% threshold.

[jianli, 2016/05/24 23:43:32]

nit: try to avoid mentioning the value in the comments because otherwise you
will have to update the comments if these constants get changed later. How
about:
// When the total storage space occupied by offline pages exceeds the
// threshold below, in terms of % of available storage, the storage clean
// up will be performed to reduce the usage.
const double kOfflinePageStorageLimit = 0.3;
// The target threshold, in terms of of available storage, which the storage
// clean up will try to reduce the usage to.
const double kOfflinePageStorageClearThreshold = 0.1;

[romax, 2016/05/25 20:05:23]

Done.

 const double kOfflinePageStorageLimit = 0.3;
 const double kOfflinePageStorageClearThreshold = 0.1;
+// If it's more than 10 minutes since the last storage clearing, it's a good
+// time to clear storage again to check for expired pages. And if a page has
+// been expired more than 21 days it should be deleted from metadata store.

[jianli, 2016/05/24 23:43:32]

ditto

[romax, 2016/05/25 20:05:23]

Done.

 const base::TimeDelta kClearStorageInterval = base::TimeDelta::FromMinutes(10);
+const base::TimeDelta kRemovePageItemInterval = base::TimeDelta::FromDays(21);
 
 class ArchiveManager;
 class ClientPolicyController;
 
 // This class is used for storage management of offline pages. It provides
 // a ClearPagesIfNeeded method which is used to clear expired offline pages
 // based on last_access_time and lifetime policy of its namespace.
 // It has its own throttle mechanism so calling the method would not be
 // guaranteed to clear the pages immediately.
 //
 // OfflinePageModel should own and control the lifecycle of this manager.
 // And this manager would use OfflinePageModel to get/remove pages.
 class OfflinePageStorageManager {
  public:
   // This interface should have no knowledge of offline page model.
   // This interface should be implemented by clients managed by storage manager.
   class Client {
    public:
     virtual ~Client() {}
 
     // Asks the client to get all offline pages and invoke |callback|.
     virtual void GetAllPages(
         const MultipleOfflinePageItemCallback& callback) = 0;
 
-    // Asks the client to delete pages based on |offline_ids| and invoke
-    // |callback|.
-    virtual void DeletePagesByOfflineId(const std::vector<int64_t>& offline_ids,
-                                        const DeletePageCallback& callback) = 0;
+    // Asks the client to mark pages with |offline_ids| as expired and the
+    // associated archive files.
+    virtual void ExpirePages(const std::vector<int64_t>& offline_ids,
+                             const base::Time& expiration_time,
+                             const DeletePageCallback& callback) = 0;

[jianli, 2016/05/24 23:43:32]

nit: try not to use DeletePageCallback since Delete in the name is not really
consistent with Expire here. Probably add a new callback and enum result. Or
rename DeletePageResult to UpdatePageResult.

[romax, 2016/05/25 20:05:23]

Done.
I realized there's no need to add a enum here. I'm going to change it to a
callback with only bool indicating if the expiration is successful or not.

+
+    // Asks the client to remove page items with |offline_ids| from metadata
+    // store and in memory mapping.
+    virtual void RemovePageItems(
+        const std::vector<int64_t>& offline_ids,
+        const base::Callback<void(bool)>& callback) = 0;
   };
 
   enum class ClearStorageResult {
     SUCCESS,         // Cleared successfully.
     UNNECESSARY,     // No expired pages.
     DELETE_FAILURE,  // Deletion failed.
   };
 
   // Callback used when calling ClearPagesIfNeeded.
   // int: the number of expired pages.
   // ClearStorageResult: result of expiring pages in storage.
-  typedef base::Callback<void(int, ClearStorageResult)> ClearPagesCallback;
+  // bool: true if removing dead pages from metadata store is successful.
+  typedef base::Callback<void(int, ClearStorageResult, bool)>
+      ClearPagesCallback;
 
   explicit OfflinePageStorageManager(Client* client,
                                      ClientPolicyController* policy_controller,
                                      ArchiveManager* archive_manager);
 
   ~OfflinePageStorageManager();
 
   // The manager would *try* to clear pages when called. It may not delete any
   // pages (if clearing condition wasn't satisfied).
   // It clears the storage (expire pages) when it's using more disk space than a
@@ skipping 20 matching lines @@
                              const ArchiveManager::StorageStats& pages);
 
   // Callback called after getting all pages from client done.
   void OnGetAllPagesDone(const ClearPagesCallback& callback,
                          const ArchiveManager::StorageStats& storage_stats,
                          const MultipleOfflinePageItemResult& pages);
 
   // Callback called after expired pages have been deleted.
   void OnExpiredPagesDeleted(const ClearPagesCallback& callback,
                              int pages_to_clear,
+                             const std::vector<int64_t>& page_ids_to_remove,
                              DeletePageResult result);
 
+  // Callback called after clearing outdated pages from client.
+  void OnExpiredPagesCleared(const ClearPagesCallback& callback,
+                             int pages_cleared,
+                             DeletePageResult result,
+                             bool success);
+
   // Gets offline IDs of all expired pages and return in |offline_ids|.

[jianli, 2016/05/24 23:43:32]

Please update the comment. Please also explain the difference between
page_ids_to_expire and page_ids_to_remove.

[romax, 2016/05/25 20:05:23]

Done.

   void GetExpiredPageIds(const MultipleOfflinePageItemResult& pages,
                          const ArchiveManager::StorageStats& stats,
-                         std::vector<int64_t>& offline_ids);
+                         std::vector<int64_t>& page_ids_to_expire,
+                         std::vector<int64_t>& page_ids_to_remove);
 
   // Determine if manager should clear pages.
   ClearMode ShouldClearPages(const ArchiveManager::StorageStats& storage_stats);
 
   // Return true if |page| is expired comparing to |now|.
   bool ShouldBeExpired(const base::Time& now, const OfflinePageItem& page);
 
   // Not owned.
   Client* client_;
 
@@ skipping 11 matching lines @@
   std::unique_ptr<base::Clock> clock_;
 
   base::WeakPtrFactory<OfflinePageStorageManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageStorageManager);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_STORAGE_MANAGER_H_