Distributed state recovery in a system having dynamic reconfiguration of participating nodes

Abstract

A method for obtaining previously stored session state data for a session between a system having a plurality of nodes and a client device includes obtaining a session identifier specifying the session and hashing the session identifier. A currently valid hash map is searched. The hash map maps a hash of the session identifier to the nodes for a current system configuration. The search is performed to identify a system node on which the session state data for the session is stored. If the session state data is not located using the currently valid hash map, at least one earlier generation hash map that is valid for a previous configuration of the system is searched. Upon identifying the system node on which the session state data is stored, the session state data from the system node is retrieved. The session state data is used to establish the session.

1 - 20 . (canceled) 
     
     
         21 . A network device in a communications network and operatively connected to a plurality of other network devices, each of the network device and the other network devices comprising respective nodes in the network, the network device comprising:
 an input configured to receive a session resume request from a client device, the session resume request associated with a prior, interrupted session between the client device and a first one of the plurality of other network devices, the prior session having associated session state data, the session resume request including information allowing the network device to obtain a session identifier specifying the prior, interrupted session; and   a processor configured to:
 hash the session identifier; 
 use the hash of the session identifier to locate a system node on which the session state data for the session is stored in a manner impervious to changes in the number of nodes in the network; and 
 use the session state data to resume delivery of the service to the client device. 
   
     
     
         22 . The network device of  claim 21  comprising a manifest manipulator. 
     
     
         23 . The network device of  claim 21  where the session identifier is a universally unique identifier (UUID) that is unique within the system for no more than a specified period of time. 
     
     
         24 . The network device of  claim 21  where the session state data includes sufficient data for the network device to resume the session. 
     
     
         25 . The network device of  claim 21  including server resources. 
     
     
         26 . The network device of  claim 21  capable of storing session state data for a session with a second client device that is ongoing at the time the input receives the session resume request. 
     
     
         27 . The network device of  claim 21  where the respective nodes are grouped into different clusters of nodes and the processor locates the system node by using a previously established system policy concerning the clusters of nodes. 
     
     
         28 . The network device of  claim 27  where the established system policy dictates that attempts to retrieve stored session state data first attempt to retrieve the stored session state data from a node in a cluster in which the first node is located. 
     
     
         29 . The network device of  claim 21  where the session state data has a shard count greater than 1. 
     
     
         30 . The network device of  claim 21 , wherein each of the nodes includes a server resource that deliver services to client devices. 
     
     
         31 . The network device of  claim 21  capable of using a selected one or more of a currently valid hash map of a current configuration of the system and an earlier generation hash map valid for a previous configuration of the system to locate the system node on which the session state data for the session is stored. 
     
     
         32 . The network device of  claim 31  configured to use the earlier generation hash map when use of the currently valid hash map fails to locate the system node on which the session state data for the session is stored. 
     
     
         33 . The network device of  claim 31 , where the processor is configured to sequentially search earlier generation hash maps until the session state data is located. 
     
     
         34 . The network device of  claim 33  where previous generations of the hash map expire and are no longer searchable after expiration of a time-to-live (TTL) for any stored session state data. 
     
     
         35 . A method implemented by a network device in a communications network and operatively connected to a plurality of other network devices, each of the network device and the other network devices comprising respective nodes in the network, the method comprising:
 receiving a session resume request from a client device, the session resume request associated with a prior, interrupted session between the client device and a first one of the plurality of other network devices, the prior session having associated session state data, the session resume request including information allowing the network device to obtain a session identifier specifying the prior, interrupted session;   hashing the session identifier;   using the hash of the session identifier to locate a system node on which the session state data for the session is stored in a manner impervious to changes in the number of nodes in the network; and   using the session state data to resume delivery of the service to the client device.   
     
     
         36 . The method of  claim 35  capable of using a selected one or more of a currently valid hash map of a current configuration of the system and an earlier generation hash map valid for a previous configuration of the system to locate the system node on which the session state data for the session is stored. 
     
     
         37 . The method of  claim 36  configured to use the earlier generation hash map when use of the currently valid hash map fails to locate the system node on which the session state data for the session is stored. 
     
     
         38 . The method of  claim 36 , where the processor is configured to sequentially search earlier generation hash maps until the session state data is located. 
     
     
         39 . The network device of  claim 38  where previous generations of the hash map expire and are no longer searchable after expiration of a time-to-live (TTL) for any stored session state data. 
     
     
         40 . The method of  claim 35  where the respective nodes are grouped into different clusters of nodes and the processor locates the system node by using a previously established system policy concerning the clusters of nodes.