PostgreSQL on Kubernetes at Scale Prague PostgreSQL Meetup Oleksii Kliukin 28-05-2018 

2 Oleksii Kliukin Postgres Engineer @ Zalando [email protected] Twitter: @hintbits About me 

3 A brief history of PostgreSQL at Zalando Live DEMO (what can possibly go wrong?) How to stop worrying (and embrace Patroni) Kubernetes: the real thing What is in the name: Postgres Operator TABLE OF CONTENTS 

4 ZALANDO: WE BRING FASHION TO PEOPLE IN 15 COUNTRIES 

5 ZALANDO AT A GLANCE as at May 2017 >300databases In data centers > 150 Postgres clusters on AWS EC2 > 200 Postgres clusters on Kubernetes 

6 Let’s start with names ` ` primary standby standby PostgreSQL (HA) cluster stream ing replication template0 postgres template1 PostgreSQL instance 

7 Brief history of PostgreSQL at Zalando 

8 Vintage (DC) and modern (AWS) PostgreSQL environments DC1 DC2 (one hour delay) NFS WAL archive AWS VPC 

Should you run your PostgreSQL inside a container? 

10 Spilo Docker image at Zalando • PGDATA on an external volume (EBS or i3/c5 NVME) • Environment-variables based configuration • One container per one EC2 instance • PostgreSQL versions from 9.4 up to 10 • Plenty of extensions (all contrib, PostGIS, timescaleDB, PL/V8, pg_cron, etc) • Additional tools (pgbouncer, pgq) • Extremely lightweight (69MB) 

github.com/zalando/spilo 

12 Cluster Security Group Auto-Scaling Availability Zone A Data Volume Root volume Master Elastic IP Cloud Formation Stack Replica DB Availability Zone B Data Volume Root volume Master DB Availability Zone C Data Volume Root volume Replica DB Replica ELB Security Group Replica Elastic Load Balancer 5432, 8008 5432, 8008 GET /replica db.zalando db-repl.zalando S3 bucket: Backup + WAL User Data: - Docker image - Backup schedule - Superuser password - Replication password - Postgres parameters Etcd 

Patroni is a secret ingredient to make it all work 

14 What is Patroni • Automatic failover solution for PostgreSQL streaming-replication • A daemon that manages one PostgreSQL instance • Keeps the state of the cluster in a DCS (Etcd, Zookeeper, Consul, Kubernetes), also referred to as a consistency layer • For new instances decides whether to initialize a new cluster or join an existing one • For running instances executes promotion/demotion when necessary • A number of additional related functions (global configuration, scheduled actions, pause mode, pg_rewind support, etc) 

15 What Patroni is not • Not an arbiter for the whole HA cluster • Not a swiss-army knife of Postgres maintenance • Not a substitute for a proper monitoring • Not a tool to use if you don’t understand how Etcd (or another DCS that you use) works. • Not a silver bullet (but tries to balance easy-to-use vs extensibility) • Not justi an internal project of Zalando (IBM Compose, Red Hat and many other companies use it) 

16 Why distributed consistency? Etcd cluster Primary candidate Primary candidate Take leader Take leader Primary candidate Take leader 

github.com/zalando/patroni 

18 • A set of open-source components running on one or more servers • A container orchestration system • An abstraction layer over your real or virtualized hardware • An “infrastructure as code” system • Automatic resource allocation • Next step after Ansible/Chef/Puppet What is Kubernetes? 

19 • An operating system • A magical way to make your infrastructure scalable • An excuse to fire your devops (someone has to configure it) • A good solution for running 2-3 servers What Kubernetes is not? 

20 Kubernetes • Node • Pod • Container • Persistent Volumes • Service/Endpoint • Labels • Secrets Terminology: traditional DC compared to Kubernetes Traditional infrastructure • Physical server • Virtual machine • Individual application • NAS/SAN • Load balancer • Application registry/hardware information • Password files 

21 Declarative resource description (manifest) apiVersion: v1 kind: Service metadata: name: nginx labels: app: nginx spec: ports: - port: 80 name: web clusterIP: None selector: app: nginx 

22 Building a PostgreSQL cluster on Kubernetes • A statefulset to bind pods with persistent volumes and provide auto-recovery • A service to route client connections • Spilo as a docker container (Patroni + PostgreSQL) for HA • Secrets to store database user passwords 

23 • At least four long YAML manifests to write • Different parts of PostgreSQL configuration spread over multiple manifests • No easy way to work with a cluster as a whole (update, delete) • Manual generation of DB objects, i.e. users, and their passwords. Manual deployment of HA PostgreSQL cluster on Kubernetes 

24 • A template for your manifests • Only one place to fill-in deployment-related values • Requires running a special pod (tiller) in your Kubernetes cluster github.com/kubernetes/charts/blob/master/incubator/patroni Initial approach to automation: HELM 

25 • Implement a controller application to act on custom resources • CRD (custom resource definitions) to describe a domain-specific object (i.e. a Postgres cluster) • Encapsulates knowledge of a human operating the service https://coreos.com/blog/introducing-operators.html Kubernetes operator pattern 

26 • Defines a custom Postgres resource • Watches instances of Postgres, creates/updates/deletes corresponding Kubernetes objects • Allows updating running-cluster resources (memory, cpu, volumes), postgres configuration • Creates databases, users and automatically generates passwords • Auto-repairs, smart rolling updates (switchover to replicas before updating the master) Zalando Postgres operator 

27 Simple Postgres manifest apiVersion: "acid.zalan.do/v1" kind: postgresql metadata: name: acid-minimal-cluster spec: teamId: "ACID" volume: size: 1Gi numberOfInstances: 2 users: # database owner zalando: - superuser - createdb # role for application foo foo_user: #databases: name->owner databases: foo: zalando postgresql: version: "10" 

28 Just a piece of cake • Operator starts pods with Spilo docker image • Operator provides environment variables to Spilo • Operator makes sure all Kubernetes objects are in sync • Spilo generates Patroni configuration • Patroni creates roles and configures PostgreSQL • Patroni makes sure there is only one master • Patroni uses Kubernetes for cluster state and leader lock • Patroni creates roles and applies configuration • Patroni changes service endpoints on failover 

deploy cluster manifest Stateful set Spilo pod Kubernetes cluster PATRONI operator pod Endpoint Service Client application operator config map Cluster secrets DB deployer create create create watch Infrastructure roles 

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31 Should you run your PostgreSQL clusters in on Kubernetes Strong interest in the community • Zalando Postgres Operator • CrunchyData Postgres Operator • Red Hat Project Atomic • KubeDB • Project Habitat 

32 Why not AWS RDS or Aurora PostgreSQL Not an easy answer :) Full control • Independent of cloud provider • Real super user available • Custom extensions, PAM • Streaming/WAL replication in and out • Local storage not supported on RDS (NVMe SSDs) Costs? Cost of development? ... 

33 • Kubernetes-native Patroni • PAM OAuth2 for PostgreSQL Bonus projects 

34 Using Kubernetes as a consistency store ● Use annotations on: ○ Pods for cluster members ○ Dedicated Endpoint for cluster configuration. ○ Service-related Endpoint for leader information. ● Reliability: always use EndPoints. ● Compatibility mode: use ConfigMaps, not Endpoints. http://patroni.readthedocs.io/en/latest/kubernetes.html 

35 ● PAM module written in C ● Open-source: https://github.com/CyberDem0n/pam-oauth2 ● Equivalent of arbitrary-long automatically generated, auto-expiring passwords. ● Can supply arbitrary key=value pairs to check in the OAuth response (i.e. realm=/employees) OAUTH2 PAM authentication 

36 OAUTH2 PAM authentication Operator configuration: pam_configuration: https://info.example.com/oauth2/tokeninfo?access_token= uid realm=/employees pam_role_name: users Operator sets PAM_OAUTH2 Spilo environment variable, adds a line to pg_hba.conf hostssl all +users all pam Spilo writes /etc/pam.d/postgresql using PAM_OAUTH2 value. 

37 Made possible by great people inside and outside of Zalando Patroni and Spilo: github.com/zalando/patroni, github.com/zalando/spilo Alexander Kukushkin, Ants Aasma, Feike Steenbergen, Josh Berkus Postgres Operator: github.com/zalando-incubator/postgres-operator Murat Kabilov, Sergey Dudoladov, Manuel Gómez, PAM Oauth2: https://github.com/CyberDem0n/pam-oauth2 Alexander Kukushkin Put it all together in a sane way: Jan Mußler 

38 “HIRE THE BEST PEOPLE YOU CAN, AND GET OUT OF THEIR WAY.“ 

We are hiring Database Engineers https://jobs.zalando.com/jobs/570376-database-engineer-postgresql 

Thank you!