System and method for maintaining a master replica for reads and writes in a data store

A computer-implemented method, comprising:

• assuming, by a replica of a replica group implemented on a computing node in a distributed data store, a role of master replica for the replica group;
• subsequent to assuming the role of master replica for the replica group, sending, by the replica, a message indicating a lease to other replicas in the replica group, wherein the lease represents an authorization of the replica to act as the master replica for the replica group for a lease period;
• refraining, by the replica, from servicing consistent read operations directed to the replica group until it is determined that the message indicating the lease has been committed by a write quorum of the other replicas of the replica group;
• in response to determining that the message indicating the lease has been committed, beginning, by the replica, to service consistent read operations that are directed to the replica group;
• assuming, by another replica of the replica group the role of master replica for the replica group, prior to the lease period expiring;
• continuing, by the replica, to service consistent read operations that are directed to the replica group during the lease period;
• and
• subsequent to the lease period expiring, beginning, by the other replica, to service consistent read operations that are directed to the replica group.

A system, comprising:

• a plurality of computing nodes, each comprising at least one processor and memory, wherein the plurality of computing nodes is configured to implement a data storage service;
• the plurality of computing nodes comprising two or more replicas that make up a replica group, wherein at most one of the replicas in the replica group can act as a master replica for the replica group at a time, and wherein replicas in the replica group that are not acting as the master replica act as secondary replicas in the replica group;
• wherein one of the computing nodes hosting the replicas is configured to:
• assume a role of master replica for the replica group;
• subsequent to assuming the role of master replica for the replica group, send a message indicating a lease to other computing nodes hosting other replicas in the replica group, wherein the lease represents an authorization of the replica to act as the master replica for the replica group for a lease period;
• refrain from servicing consistent read operations directed to the replica group until it is determined the message indicating the lease has been committed in the data storage service;
• and
• in response to determining that the message indicating the lease has been committed in the data storage service, begin to service consistent read operations that are directed to the replica group;
• wherein, prior to the lease period expiring:
• another computing node hosting another replica of the replica group is configured to assume the role of master replica for the replica group;
• the computing node hosting the replica is configured to continue to service consistent read operations that are directed to the replica group during the lease period;
• and
• subsequent to the lease period expiring, the other computing node hosting the other replica is configured to begin to service consistent read operations that are directed to the replica group.