From bfc1950df86fd0bfcb0007ab4f6e958fd4032e4e Mon Sep 17 00:00:00 2001 From: Sergey Dudoladov Date: Wed, 16 May 2018 17:25:03 +0200 Subject: [PATCH] Shorten the introduction --- README.md | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-) diff --git a/README.md b/README.md index a811d485c..fc32ebc00 100644 --- a/README.md +++ b/README.md @@ -4,27 +4,15 @@ [![Coverage Status](https://coveralls.io/repos/github/zalando-incubator/postgres-operator/badge.svg)](https://coveralls.io/github/zalando-incubator/postgres-operator) [![Go Report Card](https://goreportcard.com/badge/github.com/zalando-incubator/postgres-operator)](https://goreportcard.com/report/github.com/zalando-incubator/postgres-operator) -The Postgres operator manages PostgreSQL clusters on Kubernetes using the [operator pattern](https://coreos.com/blog/introducing-operators.html). -During the initial run it registers the [Custom Resource Definition (CRD)](https://kubernetes.io/docs/concepts/api-extension/custom-resources/#customresourcedefinitions) for Postgres. -The `postgresql` CRD is essentially the schema that describes the contents of the manifests for deploying individual -Postgres clusters using StatefulSets and [Patroni](https://github.com/zalando/patroni). +## Introduction -Once the operator is running, it performs the following actions: +The Postgres [operator](https://coreos.com/blog/introducing-operators.html) manages PostgreSQL clusters on Kubernetes: -* watches for new `postgresql` manifests and deploys new clusters -* watches for updates to existing manifests and changes corresponding properties of the running clusters -* watches for deletes of the existing manifests and deletes corresponding clusters -* acts on an update to the operator configuration itself and changes the running clusters when necessary - (i.e. the Docker image changes for a minor release update) -* periodically checks running clusters against the manifests and syncs changes +1. The operator watches additions, updates and deletions of Postgresql manifests (cluster descriptions) and changes the running clusters accordingly. For example, when a user submits a new manifest, the operator fetches that object and spawns a new Postgres cluster, including all necessary entities such as Kubernetes StatefulSets and Postgres roles. The [`postgresql` Custom Resource Definition](https://kubernetes.io/docs/concepts/api-extension/custom-resources/#customresourcedefinitions) defines settings that a cluster manifest may contain (see example). -Example: When a user creates a new custom object of type ``postgresql`` by submitting a new manifest with -``kubectl``, the operator fetches that object and creates the required Kubernetes entities to spawn a new Postgres cluster -(StatefulSets, Services, Secrets). +2. The operator also watches updates to its own configuration and alters running Postgres clusters if necessary. For instance, if a pods' Docker image is changed, the operator carries out the rolling update. That is, it re-spawns one-by-one pods from each StatefulSet it manages with the new Docker image. -Update example: After changing the Docker image inside the operator's configuration, the operator first goes to all StatefulSets -it manages and updates them with the new Docker image; afterwards, all pods from each StatefulSet are killed one by one -and the replacements are spawned automatically by each StatefulSet with the new Docker image. This is called the Rolling update. +3. Finally, the operator periodically synchronizes the actual state of each Postgres cluster with the desired state defined in the cluster's manifest. ## Quickstart @@ -55,6 +43,7 @@ We have automated these steps for you: ```bash cd postgres-operator ./run_operator_locally.sh +minikube delete ``` ## Scope