BDR-Always-ON

EDB Postgres Distributed 4 or below in an Always-ON configuration, suitable for use in test and production.

This architecture requires a subscription to the legacy 2ndQuadrant repositories, and some options require a subscription to EDB Repos 1.0. See How TPA uses 2ndQuadrant and EDB repositories

for more detail on this topic.

The BDR-Always-ON architecture has four variants, which can be selected with the --layout configure option:

  1. bronze: 2×bdr+primary, bdr+witness, barman, 2×harp-proxy

  2. silver: bronze, with bdr+witness promoted to bdr+primary, and barman moved to separate location

  3. gold: two symmetric locations with 2×bdr+primary, 2×harp-proxy, and barman each; plus a bdr+witness in a third location

  4. platinum: gold, but with one bdr+readonly (logical standby) added to each of the main locations

You can check EDB’s Postgres-BDR Always On Architectures whitepaper

for the detailed layout diagrams.

This architecture is meant for use with BDR versions 3.6, 3.7, and 4.

Cluster configuration

[tpa]$ tpaexec configure ~/clusters/bdr \
         --architecture BDR-Always-ON \
         --layout gold \
         --harp-consensus-protocol bdr \
         --platform aws --region eu-west-1 --instance-type t3.micro \
         --distribution Debian-minimal

You must specify --architecture BDR-Always-ON . (In the example above, it is the only option required to produce a working configuration.)

You also must specify --layout layoutname to set one of the supported BDR use-case variations. The current options are bronze, silver, gold, and platinum. The bronze, gold and platinum layouts have a BDR witness node to ensure odd number of nodes for Raft consensus majority. Witness nodes do not participate in the data replication.

You must specify --harp-consensus-protocol protocolname . The supported protocols are bdr and etcd; see Configuring HARP for more details.

You may optionally specify --bdr-database dbname to set the name of the database with BDR enabled (default: bdrdb).

You may optionally specify --enable-camo to set the pair of BDR primary instances in each region to be each other’s CAMO partners.

Please note we enable HARP2 by default in BDR-Always-ON architecture.

You may also specify any of the options described by tpaexec help configure-options .