METHOD AND SYSTEM FOR READING CONSISTENT DATA FROM A MULTI-MASTER REPLICATED DATABASE

摘要

Methods, systems, and architectures are provided for allowing a consistent view (e.g., read-after-write) from a replicated database that uses asynchronous replication (e.g., eventual consistency of data across related databases) without the use of a master replicated database. A replication “low water mark” for a replica includes a timestamp of the most recent write that has fully replicated to the replica, and therefore indicates that the replica is current as of time “X”. By using the difference between the present moment in time (e.g., “now”) and the last write timestamp received via replication, it is possible to determine how delayed a given replica is.

主权项

1. A method comprising: occur
reading data contained at a first replicated database, wherein the data includes a timestamp of a last replicated write to the first replicated database; obtaining a per-replica timestamp from the first replicated database, wherein the per-replica timestamp indicates when most recent writes have fully replicated to the first replicated database from one or more other replicated databases associated with the first replicated database; comparing the per-replica timestamp from the first replicated database with a last write timestamp of a data structure, wherein the last write timestamp of the data structure indicates when last writes of complete data to the one or more other replicated databases have occurred; when the timestamp of the data structure is greater than the per-replica timestamp from the first replicated database:
determining that the first replicated database is missing data written to the one or more other replicated databases; andissuing a data read from the one or more other replicated databases associated with the first replicated database to backfill the missing data.