Reduce unneeded policy fetches by detecting expired invalidations.

chrome/browser/policy/cloud/cloud_policy_invalidator.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 CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_INVALIDATOR_H_
 #define CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_INVALIDATOR_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 30 matching lines @@
 
   // The default, min and max values for max_fetch_delay_.
   static const int kMaxFetchDelayDefault;
   static const int kMaxFetchDelayMin;
   static const int kMaxFetchDelayMax;
 
   // The grace period, in seconds, to allow for invalidations to be received
   // once the invalidation service starts up.
   static const int kInvalidationGracePeriod;
 
+  // Time, in seconds, for which unknown version invalidations are ignored after
+  // fetching a policy.
+  static const int kUnknownVersionIgnorePeriod;
+
+  // The max tolerated discrepancy, in minutes, between policy timestamps and
+  // invalidation timestamps when determining if an invalidation is expired.
+  static const int kMaxInvalidationTimeDelta;

[Joao da Silva, 2014/04/08 12:31:59]

I'd suggest having both times in seconds, up to you.

[Steve Condie, 2014/04/08 18:09:39]

Done.

+
   // |core| is the cloud policy core which connects the various policy objects.
   // It must remain valid until Shutdown is called.
   // |task_runner| is used for scheduling delayed tasks. It must post tasks to
   // the main policy thread.
   // |clock| is used to get the current time.
   CloudPolicyInvalidator(
       CloudPolicyCore* core,
       const scoped_refptr<base::SequencedTaskRunner>& task_runner,
       scoped_ptr<base::Clock> clock);
   virtual ~CloudPolicyInvalidator();
@@ skipping 56 matching lines @@
   // response to an invalidation with a missing payload.
   void RefreshPolicy(bool is_missing_payload);
 
   // Acknowledge the latest invalidation.
   void AcknowledgeInvalidation();
 
   // Determines if the given policy is different from the policy passed in the
   // previous call.
   bool IsPolicyChanged(const enterprise_management::PolicyData* policy);
 
+  // Determine if an invalidation has expired.
+  // |version| is the version of the invalidation, or zero for unknown.
+  bool IsInvalidationExpired(int64 version);
+
   // Get the kMetricPolicyRefresh histogram metric which should be incremented
   // when a policy is stored.
   int GetPolicyRefreshMetric(bool policy_changed);
 
+  // Get the kMetricPolicyInvalidations histogram metric which should be
+  // incremented when an invalidation is received.
+  int GetInvalidationMetric(bool is_missing_payload, bool is_expired);
+
   // Determine if invalidations have been enabled longer than the grace period.
   bool GetInvalidationsEnabled();
 
   // The state of the object.
   enum State {
     UNINITIALIZED,
     STOPPED,
     STARTED,
     SHUT_DOWN
   };
@@ skipping 60 matching lines @@
   // A thread checker to make sure that callbacks are invoked on the correct
   // thread.
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(CloudPolicyInvalidator);
 };
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_INVALIDATOR_H_