Methods, devices and systems for non-disruptive upgrades to a distributed coordination engine in a distributed computing environment

A computer-implemented method of maintaining consistency of client applications on a plurality of server nodes, comprising:

• providing a first version of a distributed coordination engine (DConE), coupled to at least one of the plurality of server nodes and, at the first version of the DConE:
• receiving proposals on an input queue, reaching agreements on the proposals and outputting a first ordering of agreements on an output queue coupled to the at least one of the plurality of server nodes, the first ordering of agreements specifying an order in which the client applications are to execute constituent agreements of the first ordering of agreements and correspondingly update their respective states;
• and
• monitoring the input queue for a ChangeVersion proposal, reaching agreement on the ChangeVersion proposal, outputting the agreement on the ChangeVersion proposal on the output queue and thereafter stop reaching any further agreements on the proposals on the input queue the ChangeVersion proposal being configured to direct a changeover of subsequent proposals on the input queue from the first version of DConE to a second version of the DConE;
• providing the second version of the DConE coupled to the at least one of the plurality of server nodes and, at the second version of the DConE:
• after the agreement corresponding to the ChangeVersion proposal has been output to the output queue, reaching agreements on the proposals on the input queue and outputting a second ordering of agreements on the output queue, beginning with the agreement corresponding to the ChangeVersion proposal, the second ordering of agreements including proposals on which agreements have been reached and specifying an order in which the client applications are to execute constituent agreements of the second ordering of agreements and correspondingly update their respective states and
• sending any agreed-upon proposal, received from the first version of the DConE after receipt of the agreement on the ChangeVersion proposal, back to the second version of the DConE via the input queue to enable the second version of the DConE to reach agreement thereon.

A computer-implemented method of maintaining consistency of client applications on a plurality of server nodes comprises:

• providing a first version of a distributed coordination engine (DConE);
• in the first version of the DConE, reaching agreements on proposals and generating a first ordering of agreements that specifies an order in which the client applications are to execute the proposals agreed-upon by the first version of the DConE and correspondingly update their respective states;
• providing a second version of a DConE;
• reaching agreement on a ChangeVersion proposal in the first version of the DConE, the ChangeVersion proposal being configured to direct a changeover of subsequent proposals on the input queue from the first version of DConE to the second version of the DConE;
• stopping reaching agreements on proposals in the second version of the DConE after agreement is reached on the ChangeVersion proposal and generating a second ordering of agreements that specifies an order in which the client applications are to execute the proposals agreed-upon by the second version of the DConE and correspondingly update their respective states;
• and
• sending any agreed-upon proposal, received from the first version of the DConE after agreement on the ChangeVersion proposal is reached, back to the second version of the DConE to enable the second version of the DConE to reach agreement thereon.