Implement cloud policy invalidations using the invalidation service framework.

chrome/browser/policy/cloud/cloud_policy_store.h

 // Copyright (c) 2012 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_STORE_H_
 #define CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_STORE_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
@@ skipping 55 matching lines @@
   }
   bool is_managed() const {
     return policy_.get() &&
            policy_->state() == enterprise_management::PolicyData::ACTIVE;
   }
   Status status() const { return status_; }
   CloudPolicyValidatorBase::Status validation_status() const {
     return validation_status_;
   }
 
+  // Returns true if the latest policy loaded was different from the previous
+  // policy.
+  bool policy_changed() const {
+    return policy_changed_;
+  }
+
   // Store a new policy blob. Pending load/store operations will be canceled.
   // The store operation may proceed asynchronously and observers are notified
   // once the operation finishes. If successful, OnStoreLoaded() will be invoked
   // on the observers and the updated policy can be read through policy().
   // Errors generate OnStoreError() notifications.
   virtual void Store(
       const enterprise_management::PolicyFetchResponse& policy) = 0;
 
   // Load the current policy blob from persistent storage. Pending load/store
   // operations will be canceled. This may trigger asynchronous operations.
   // Upon success, OnStoreLoaded() will be called on the registered observers.
   // Otherwise, OnStoreError() reports the reason for failure.
   virtual void Load() = 0;
 
   // Registers an observer to be notified when policy changes.
   void AddObserver(Observer* observer);
 
   // Removes the specified observer.
   void RemoveObserver(Observer* observer);
 
+  // The invalidation version of the last policy stored. This value can be read
+  // by observers to determine which version of the policy is now available.
+  int64 invalidation_version() {
+    return invalidation_version_;
+  }
+
+  // Set the invalidation version. This method should be called immediately
+  // before the Store method.
+  void set_invalidation_version(int64 invalidation_version) {

[Joao da Silva, 2013/07/23 20:44:47]

Can this be part of the Store() method? Or maybe have a new
StoreWithVersion(policy, version) method?

If this is combined with Store() then it can't be used in the wrong order.

[Steve Condie, 2013/07/24 01:42:04]

I agree it's better to make it one call. I considered doing it but resisted
because it's a virtual method and would seem to dictate replacing the public
method and making the virtual method a protected member which would involve
touching all the subclasses, etc. However, I like your idea of just adding a new
public method to avoid touching subclasses so I did that.

+    invalidation_version_ = invalidation_version;
+  }
  protected:
   // Invokes the corresponding callback on all registered observers.
   void NotifyStoreLoaded();
   void NotifyStoreError();
 
+  // Subclasses for which policy_changed() functionality is desired must call
+  // this method when |policy_| is updated. |hash_value| must contain a hash
+  // value calculated on the policy value, or be zero if there is no policy.
+  void SetPolicyHashValue(uint32 hash_value);

[Joao da Silva, 2013/07/23 20:44:47]

A subclass may forget to call this, or do it in the wrong order.

You can just compute the hash of the current |policy_| at NotifyStoreLoaded(),
which is called whenever the policy changes, and then compare that to the
previous hash. If you do that then this function isn't needed, nor the
hash_value changes in the CloudPolicyValidator.

You may have to serialize |policy_| to do that.

[Steve Condie, 2013/07/24 01:42:04]

Done.

+
   // Decoded version of the currently effective policy.
   PolicyMap policy_map_;
 
   // Currently effective policy.
   scoped_ptr<enterprise_management::PolicyData> policy_;
 
   // Latest status code.
   Status status_;
 
   // Latest validation status.
   CloudPolicyValidatorBase::Status validation_status_;
 
  private:
   // Whether the store has completed asynchronous initialization, which is
   // triggered by calling Load().
   bool is_initialized_;
 
+  // The hash value of the current policy. This is used to determine when the
+  // policy changes.
+  uint32 hash_value_;
+
+  bool policy_changed_;
+
+  int64 invalidation_version_;
+
   ObserverList<Observer, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(CloudPolicyStore);
 };
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_CLOUD_CLOUD_POLICY_STORE_H_