80 lines
4.4 KiB
Markdown
80 lines
4.4 KiB
Markdown
# Concepts
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The Postgres [operator](https://coreos.com/blog/introducing-operators.html)
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manages PostgreSQL clusters on Kubernetes (K8s):
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1. The operator watches additions, updates, and deletions of PostgreSQL cluster
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manifests and changes the running clusters accordingly. For example, when a
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user submits a new manifest, the operator fetches that manifest and spawns a
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new Postgres cluster along with all necessary entities such as K8s
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StatefulSets and Postgres roles. See this
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[Postgres cluster manifest](../manifests/complete-postgres-manifest.yaml)
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for settings that a manifest may contain.
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2. The operator also watches updates to [its own configuration](../manifests/configmap.yaml)
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and alters running Postgres clusters if necessary. For instance, if a pod
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docker image is changed, the operator carries out the rolling update. That
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is, the operator re-spawns one-by-one pods of each StatefulSet it manages
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with the new Docker image.
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3. Finally, the operator periodically synchronizes the actual state of each
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Postgres cluster with the desired state defined in the cluster's manifest.
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4. The operator aims to be hands free and configuration happens only via
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manifests and its own config. This enables easy integration in automated
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deploy pipelines with no access to K8s directly.
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## Scope
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The scope of the Postgres Operator is on provisioning, modifying configuration
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and cleaning up Postgres clusters that use Patroni, basically to make it easy
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and convenient to run Patroni based clusters on K8s. The provisioning
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and modifying includes K8s resources on one side but also e.g. database
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and role provisioning once the cluster is up and running. We try to leave as
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much work as possible to K8s and to Patroni where it fits, especially
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the cluster bootstrap and high availability. The operator is however involved
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in some overarching orchestration, like rolling updates to improve the user
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experience.
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Monitoring of clusters is not in scope, for this good tools already exist from
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ZMON to Prometheus and more Postgres specific options.
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## Overview of involved entities
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Here is a diagram, that summarizes what would be created by the operator, when a
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new Postgres cluster CRD is submitted:
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This picture is not complete without an overview of what is inside a single
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cluster pod, so let's zoom in:
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These two diagrams should help you to understand the basics of what kind of
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functionality the operator provides.
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## Status
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This project is currently in active development. It is however already
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[used internally by Zalando](https://jobs.zalando.com/tech/blog/postgresql-in-a-time-of-kubernetes/)
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in order to run Postgres clusters on K8s in larger numbers for staging
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environments and a growing number of production clusters. In this environment
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the operator is deployed to multiple K8s clusters, where users deploy
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manifests via our CI/CD infrastructure or rely on a slim user interface to
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create manifests.
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Please, report any issues discovered to https://github.com/zalando/postgres-operator/issues.
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## Talks
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1. "Building your own PostgreSQL-as-a-Service on Kubernetes" talk by Alexander Kukushkin, KubeCon NA 2018: [video](https://www.youtube.com/watch?v=G8MnpkbhClc) | [slides](https://static.sched.com/hosted_files/kccna18/1d/Building%20your%20own%20PostgreSQL-as-a-Service%20on%20Kubernetes.pdf)
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2. "PostgreSQL and Kubernetes: DBaaS without a vendor-lock" talk by Oleksii Kliukin, PostgreSQL Sessions 2018: [video](https://www.youtube.com/watch?v=q26U2rQcqMw) | [slides](https://speakerdeck.com/alexeyklyukin/postgresql-and-kubernetes-dbaas-without-a-vendor-lock)
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3. "PostgreSQL High Availability on Kubernetes with Patroni" talk by Oleksii Kliukin, Atmosphere 2018: [video](https://www.youtube.com/watch?v=cFlwQOPPkeg) | [slides](https://speakerdeck.com/alexeyklyukin/postgresql-high-availability-on-kubernetes-with-patroni)
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4. "Blue elephant on-demand: Postgres + Kubernetes" talk by Oleksii Kliukin and Jan Mussler, FOSDEM 2018: [video](https://fosdem.org/2018/schedule/event/blue_elephant_on_demand_postgres_kubernetes/) | [slides (pdf)](https://www.postgresql.eu/events/fosdem2018/sessions/session/1735/slides/59/FOSDEM%202018_%20Blue_Elephant_On_Demand.pdf)
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5. "Kube-Native Postgres" talk by Josh Berkus, KubeCon 2017: [video](https://www.youtube.com/watch?v=Zn1vd7sQ_bc)
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