The Postgres operator manages PostgreSQL clusters on Kubernetes:
The operator watches additions, updates, and deletions of PostgreSQL cluster manifests and changes the running clusters accordingly. For example, when a user submits a new manifest, the operator fetches that manifest and spawns a new Postgres cluster along with all necessary entities such as Kubernetes StatefulSets and Postgres roles. See this Postgres cluster manifest for settings that a manifest may contain.
The operator also watches updates to its own configuration and alters running Postgres clusters if necessary. For instance, if a pod docker image is changed, the operator carries out the rolling update. That is, the operator re-spawns one-by-one pods of each StatefulSet it manages with the new Docker image.
Finally, the operator periodically synchronizes the actual state of each Postgres cluster with the desired state defined in the cluster's manifest.
The scope of the postgres operator is on provisioning, modifying configuration and cleaning up Postgres clusters that use Patroni, basically to make it easy and convenient to run Patroni based clusters on Kubernetes. The provisioning and modifying includes Kubernetes resources on one side but also e.g. database and role provisioning once the cluster is up and running. We try to leave as much work as possible to Kubernetes and to Patroni where it fits, especially the cluster bootstrap and high availability. The operator is however involved in some overarching orchestration, like rolling updates to improve the user experience.
Monitoring of clusters is not in scope, for this good tools already exist from ZMON to Prometheus and more Postgres specific options.
This project is currently in active development. It is however already used internally by Zalando in order to run Postgres clusters on Kubernetes in larger numbers for staging environments and a growing number of production clusters. In this environment the operator is deployed to multiple Kubernetes clusters, where users deploy manifests via our CI/CD infrastructure or rely on a slim user interface to create manifests.
Please, report any issues discovered to https://github.com/zalando-incubator/postgres-operator/issues.
"Kube-Native Postgres" talk by Josh Berkus, KubeCon 2017: video