Add prefetch support to AffiliationBackend.

components/password_manager/core/browser/facet_manager.h

 // Copyright 2015 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_PASSWORD_MANAGER_CORE_BROWSER_FACET_MANAGER_H_
 #define COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_FACET_MANAGER_H_
 
+#include <set>
+#include <vector>
+
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "components/password_manager/core/browser/affiliation_service.h"
 #include "components/password_manager/core/browser/affiliation_utils.h"
 
 namespace base {
+class Clock;
 class TaskRunner;
 }  // namespace base
 
 namespace password_manager {
 
 class FacetManagerHost;
 
 // Part of AffiliationBackend that encapsulates the state and logic required for
-// handling GetAffiliations() requests in regard to a single facet.
+// handling requests in regard to a single facet.
 //
 // In contrast, the AffiliationBackend itself implements the FacetManagerHost
 // interface to provide shared functionality needed by all FacetManagers.
 class FacetManager {
  public:
-  // The |backend| must outlive this object.
-  FacetManager(FacetManagerHost* backend, const FacetURI& facet_uri);
+  // Both the |backend| and |clock| must outlive this object.
+  FacetManager(const FacetURI& facet_uri,
+               FacetManagerHost* backend,
+               base::Clock* clock);
   ~FacetManager();
 
+  // Facet-specific implementations for methods in AffiliationService of the
+  // same name. See documentation in affiliation_service.h for details:
+  void GetAffiliations(
+      bool cached_only,
+      const AffiliationService::ResultCallback& callback,
+      const scoped_refptr<base::TaskRunner>& callback_task_runner);
+  void Prefetch(const base::Time& keep_fresh_until);
+  void CancelPrefetch(const base::Time& keep_fresh_until);
+
   // Called when |affiliation| information regarding this facet has just been
   // fetched from the Affiliation API.
   void OnFetchSucceeded(const AffiliatedFacetsWithUpdateTime& affiliation);
 
+  // Called by the backend when the time specified in RequestNotificationAtTime
+  // has come to pass, so that |this| can perform delayed administrative tasks.
+  void NotifyAtRequestedTime();
+
   // Returns whether this instance has becomes redundant, that is, it has no
   // more meaningful state than a newly created instance would have.
   bool CanBeDiscarded() const;
 
   // Returns whether or not affiliation information relating to this facet needs
   // to be fetched right now.
   bool DoesRequireFetch() const;
 
-  // Facet-specific implementations for methods in AffiliationService of the
-  // same name. See documentation in affiliation_service.h for details:
-  void GetAffiliations(
-      bool cached_only,
-      const AffiliationService::ResultCallback& callback,
-      const scoped_refptr<base::TaskRunner>& callback_task_runner);
-
  private:
   struct RequestInfo;
 
-  // Returns the time when cached data for this facet will expire. The data is
-  // already considered expired at the returned microsecond.
-  base::Time GetCacheExpirationTime() const;
+  // Returns the time when the cached data for this facet will become stale.
+  // The data is considered stale already in the time quantum.

[Mike West, 2015/02/25 10:33:06]

What is a "time quantum"?

[engedy, 2015/03/10 11:01:00]

That was a typo. Rephrased entirely.

+  base::Time GetCacheHardExpiryTime() const;
 
-  // Returns whether or not the cache has fresh data for this facet.
+  // Returns the time when cached data for this facet becomes near-stale.
+  // The data is considered near-stale already in the returned time quantum.
+  base::Time GetCacheSoftExpiryTime() const;
+
+  // Returns whether or not cached data for this facet is fresh (not stale).
   bool IsCachedDataFresh() const;

[Mike West, 2015/02/25 10:33:06]

It might be worthwhile to add a public accessor for the state of the cache, and
unittests specifically around that

[engedy, 2015/03/10 11:01:00]

Done.

 
+  // Returns the maximum of |keep_fresh_untils_|, or the NULL time if the set is
+  // empty.
+  base::Time GetMaximumKeepFreshUntil() const;
+
+  // Returns the next time affiliation data for this facet needs to be fetched
+  // due to active prefetch requests, or base::Time::Max() if not at all.
+  base::Time GetNextRequiredFetchTimeDueToPrefetch() const;
+
   // Posts the callback of the request described by |request_info| with success.
   static void ServeRequestWithSuccess(const RequestInfo& request_info,
                                       const AffiliatedFacets& affiliation);
 
   // Posts the callback of the request described by |request_info| with failure.
   static void ServeRequestWithFailure(const RequestInfo& request_info);
 
+  FacetURI facet_uri_;
   FacetManagerHost* backend_;
-  FacetURI facet_uri_;
+  base::Clock* clock_;
 
   // The last time affiliation information was fetched for this facet, i.e. the
   // freshness of the data in the cache. If there is no corresponding data in
   // the database, this will contain the NULL time. Otherwise, the update time
   // in the database should match this value; it is stored to reduce disk I/O.
   base::Time last_update_time_;
 
   // Contains information about the GetAffiliations() requests that are waiting
   // for the result of looking up this facet.
   std::vector<RequestInfo> pending_requests_;
 
+  // Keeps track of |keep_fresh_until| thresholds corresponding to Prefetch()
+  // requests for this facet. Affiliation information for this facet must be
+  // kept fresh by periodic refetches until at least the maximum time in this
+  // set (exclusive).
+  //
+  // This is not a single timestamp but rather a multiset so that cancellation
+  // of individual prefetches can be supported even if there are two requests
+  // with the same |keep_fresh_until| threshold.
+  std::multiset<base::Time> keep_fresh_untils_;
+
   DISALLOW_COPY_AND_ASSIGN(FacetManager);
 };
 
 }  // namespace password_manager
 #endif  // COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_FACET_MANAGER_H_