Architecture

Component Overview

Here is how PostgreSQL module components and their interactions. From top to bottom:

• Cluster DNS is resolved by DNSMASQ on infra nodes
• Cluster VIP is manged by vip-manager, which will bind to cluster primary.
  • vip-manager will acquire cluster leader info written by patroni from etcd cluster directly
• Cluster services are exposed by Haproxy on nodes, services are distinguished by node ports (543x).
  • Haproxy port 9101: monitoring metrics & stats & admin page
  • Haproxy port 5433: default service that routes to primary pgbouncer: primary
  • Haproxy port 5434: default service that routes to replica pgbouncer: replica
  • Haproxy port 5436: default service that routes to primary postgres: default
  • Haproxy port 5438: default service that routeroutesto offline postgres: offline
  • HAProxy will route traffic based on health check information provided by patroni.
• Pgbouncer is a connection pool middleware that buffers connections, exposes extra metrics, and brings extra flexibility @ port 6432
  • Pgbouncer is stateless and deployed with the Postgres server in a 1:1 manner through a local unix socket.
  • Production traffic (Primary/Replica) will go through pgbouncer by default (can be skipped by pg_default_service_dest )
  • Default/Offline service will always bypass pgbouncer and connect to target Postgres directly.
• Postgres provides relational database services @ port 5432
  • Install PGSQL module on multiple nodes will automatically form a HA cluster based on streaming replication
  • PostgreSQL is supervised by patroni by default.
• Patroni will supervise PostgreSQL server @ port 8008 by default
  • Patroni spawn postgres servers as the child process
  • Patroni uses etcd as DCS: config storage, failure detection, and leader election.
  • Patroni will provide Postgres information through a health check. Which is used by HAProxy
  • Patroni metrics will be scraped by prometheus on infra nodes
• PG Exporter will expose postgres metrics @ port 9630
  • PostgreSQL’s metrics will be scraped by prometheus on infra nodes
• Pgbouncer Exporter will expose pgbouncer metrics @ port 9631
  • Pgbouncer’s metrics will be scraped by prometheus on infra nodes
• pgBackRest will work on the local repo by default (pgbackrest_method)
  • If local (default) is used as the backup repo, pgBackRest will create local repo under the primary’s pg_fs_bkup
  • If minio is used as the backup repo, pgBackRest will create the repo on the dedicated MinIO cluster in pgbackrest_repo.minio
• Postgres-related logs (postgres,pgbouncer,patroni,pgbackrest) are exposed by promtail @ port 9080
  • Promtail will send logs to Loki on infra nodes