EDB Postgres Distributed provides loosely-coupled multi-master logical replication using a mesh topology. This means that you can write to any server and the changes are sent directly, row-by-row to all the other servers that are part of the same mesh.
EDB Postgres Distributed consists of several components that make the whole cluster work.
Three different Postgres distributions can be used:
- PostgreSQL - open source
- EDB Postgres Extended Server - PostgreSQL compatible and optimized for replication
- EDB Postgres Advanced Server - Oracle compatible, optimized for replication, and additional enterprise features
What Postgres distribution and version is right for you depends on the features you need. See the feature matrix in Choosing a Postgres distribution for detailed comparison.
A Postgres server with the BDR extension installed is referred to as a BDR node. BDR nodes can be either data nodes or witness nodes.
Witness nodes don't participate in data replication and are only used as a tie-breaker for consensus.
HARP is connection management tool for a EDB Postgres Distributed cluster.
It leverages consensus-driven quorum to determine the correct connection end-point in a semi-exclusive manner to prevent unintended multi-node writes from an application. This reduces the potential for data conflicts.