Consensus system downtime recovery

A computer-implemented consensus method to be implemented on a blockchain maintained by a number (N) of nodes, wherein one of the nodes acts as a primary node and the other (N−1) nodes act as backup nodes, and the method is performed by one of the backup nodes, the method comprising:

• obtaining a pre-prepare message from the primary node;
• multicasting a prepare message to at least some of the primary node and the other (N−2) backup nodes, the prepare message indicating an acceptance of the pre-prepare message;
• obtaining (Q−1) or more prepare messages respectively from (Q−1) or more of the backup nodes, wherein Q (quorum) is (N+F+1)/2 rounded up to the nearest integer, and F is (N−1)/3 rounded down to the nearest integer;
• storing the pre-prepare message and the (Q−1) or more prepare messages;
• multicasting a commit message to at least some of the primary node and the other backup nodes, the commit message indicating that the one backup node agrees to the (Q−1) or more prepare messages;
• and
• obtaining, respectively from Q or more nodes among the primary node and the backup nodes, Q or more commit messages each indicating that the corresponding node agrees to (Q−1) or more prepare messages received by the corresponding node.

A consensus system for maintaining a blockchain, wherein a number of N nodes maintain the blockchain with one of the N nodes acting as a primary node and the other (N−1) nodes acting as backup nodes, the consensus system acting as one of the (N−1) backup nodes and comprising one or more processors and one or more non-transitory computer-readable memories coupled to the one or more processors and configured with instructions executable by the one or more processors to cause the system to perform operations comprising:

• obtaining a pre-prepare message from the primary node;
• multicasting a prepare message to at least some of the primary node and the other (N−2) backup nodes, the prepare message indicating an acceptance of the pre-prepare message;
• obtaining (Q−1) or more prepare messages respectively from (Q−1) or more of the backup nodes, wherein Q (quorum) is (N+F+1)/2 rounded up to the nearest integer, and F is (N−1)/3 rounded down to the nearest integer;
• storing the pre-prepare message and the (Q−1) or more prepare messages;
• multicasting a commit message to at least some of the primary node and the other backup nodes, the commit message indicating that the one backup node agrees to the (Q−1) or more prepare messages;
• and
• obtaining, respectively from Q or more nodes among the primary node and the backup nodes, Q or more commit messages each indicating that the corresponding node agrees to (Q−1) or more prepare messages received by the corresponding node.

A non-transitory computer-readable storage medium for maintaining a blockchain, wherein a number of N nodes maintain the blockchain with one of the N nodes acting as a primary node and the other (N−1) nodes acting as backup nodes, the storage medium being associated with one of the (N−1) backup nodes and configured with instructions executable by one or more processors to cause the one or more processors to perform operations comprising:

• obtaining a pre-prepare message from the primary node;
• multicasting a prepare message to at least some of the primary node and the other (N−2) backup nodes, the prepare message indicating an acceptance of the pre-prepare message;
• obtaining (Q−1) or more prepare messages respectively from (Q−1) or more of the backup nodes, wherein Q (quorum) is (N+F+1)/2 rounded up to the nearest integer, and F is (N−1)/3 rounded down to the nearest integer;
• storing the pre-prepare message and the (Q−1) or more prepare messages;
• multicasting a commit message to at least some of the primary node and the other backup nodes, the commit message indicating that the one backup node agrees to the (Q−1) or more prepare messages;
• and
• obtaining, respectively from Q or more nodes among the primary node and the backup nodes, Q or more commit messages each indicating that the corresponding node agrees to (Q−1) or more prepare messages received by the corresponding node.