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• JAVA API:
  ignite.encryption().changeMasterKey(String masterKeyId)  - starts master key rotation process.
  String ignite.encryption().getMasterKeyId()  - gets current master key id.
  
  
• JMX:
  changeMasterKey(String masterKeyId)  - starts master key rotation process.
  String getMasterKeyId()   - gets current master key id.
  
  
• CLI:
  # Starts master key rotation.
  control.sh --encryption change_master_key newMasterKeyId 
  
  # Displays cluster's current master key id.
  control.sh --encryption get_master_key 
  
  # Starts ignite with MK recovery process. See details.
  ignite.sh --change-master-key newMasterKeyId 

Process description 

1. Check that the cluster is active (WAL should be available for a write to correctly log changes and survive cluster restarts). Otherwise, throw an error.
2. A node creates the ChangeMasterKeyMessage  message and sent it by discovery as a custom event. The goal is to verify that all nodes have the same master key. 
   
   1. Initiating message should contain: 
      1. New master key id. 
      2. New master key hash.
   2. When server node processed message following actions are executed: 
      1. It obtain hash of new master key.
      2. Compares it with the one in message
      3. If it differs then error added to the message.
      4. Store locally master key id and hash.
3. If on step1 there are some errors we log it and cancel process. Otherwise got to step3.
4. The ChangeMasterKeyFinishMessage  action message is sent by discovery as a custom event.
   1. Action message sould contain:
      
      1. New master key id.
      2. New master key hash.
   2. When server node processed message following actions are executed: 
      1. Checks that master key id and hash is the same as it was taken from the first message. Otherwice, we log it and cancel process.
      2. Blocks creation of encrypted cache key.
      3. Reencrypt all cache group keys with new master key in a temporary datastructure. No changes in MetaStore.
      4. Create WAL logical record (ChangeMasterKeyRecord ) that consist of:
         1. New master key id
         2. Reenctyped cache group keys.
      5. Write cache group keys to MetaStore .
      6. Unblock creation of encrypted cache key. 

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