PGConf.ASIA 2019 Bali - Building PostgreSQL as a Service with Kubernetes - Takahiro Kobayashi
- 1. Building PostgreSQL as a Service with Kubernetes PGConf.Asia 2019 2019/9/9 @tzkb
- 2. 3 My Actitvities PGConf.Asia 2018 @Tokyo A guide of PostgreSQL on Kuberntes - In terms of Storage - CloudNativeDays Tokyo 2019 The Future of Database on Kubernetes - What run with Cloud Native Storage - ＋ ＝∞
- 3. 4 Agenda 1. Recap: What is Kubernetes? 2. The Issues for Database on Kubernetes 3. How to run your PostgreSQL on K8s 4. Kubernetes becomes The Platform
- 4. 6 1. Recap: What is Kubernetes?
- 5. 7 What is Kubernetes? Pod Pod Pod Pod Pod • Kubernetes(K8s) is the orchestrator tool for containers. It has 3 features below. • Declarative config • Auto-healing • Immutable Database is not Immutable.
- 6. 8 Better to handle the database system by Kubernetes? Node Node Node Master Slave Replicate • The database usually has a state that is not easy to maintain by Kubernetes. <Disadvantage for DB> • Necessary to startup in turn. • Must never lose their data. • Handle the database as pets.
- 7. 9 Example of Database on Kubernetes: Vitess VTtablet VTtablet VTtablet VTgate app app app SQL SQL SQL • Vitess that used on YouTube is the CNCF incubating project. • Vitess provides MySQL sharding in K8s. • VTgate and VTtablet can scale by K8s. • When terminating a component abnormally, Kubernetes repair it automatically.
- 8. 10 The choice: How to manage your database Compute Storage Managed Amazon Aurora Amazon Redshift Amazon RDS on Cloud on Kubernetes • You can choose to manage the database by yourself or else.
- 9. 17 2. The Issues for Database on Kubernetes
- 10. 18 Kubernetes is the Distributed Systems • Developed as following a distributed architecture. • When doesn’t a node reply – Network partition? – Process failure? – Node failure? • If the disk resource attached, harder to determine. FailOver?
- 11. 20 Database Architects are familiar with Clustering “If you don’t know the status, it’s okay. We act on the premise of failsafe.” “No need to share resources. Right?” “Both have long been known for database clustering.”
- 12. 21 Basic: Database Clustering HA (Active/Standby) １ Sharding Replication (Active/Active) ２or more Instances Redundancy 2 or more Shared Disk Log Shipping --- × Scaleout? Read Read/ Write Failover (Fencing) Availability Promotion (Election) --- • There are differences to build a DB cluster with some nodes.
- 13. 22 Clustering #1: HA • With Linux-HA • Use high-available shared storage <Worst Case> • Multiple writes to storage <Solution> • Fencing VIP Linux-HA Controller Controller • It's been used since before Linux but helpful.
- 14. 23 Note: Fencing VIP Linux-HA Controller Controller < When Detecting Node Failure > 1. Forced node power off i. Definite processes stop ii. Unmount storage iii. Detach virtual IP 2. PostgreSQL starts to run on the standby node. • Failed node is isolated from resources = Fencing
- 15. 24 Clustering #2: Replication WAL • The master can Read/Write, Slaves are Read-Only. • Data synchronization by WAL transmission <Worst Case> • 2 or more Masters <Solution> • Leader Election • Redundancy built into PostgreSQL = Streaming Replication Master SlaveSlave
- 16. 25 Note: Leader Election WAL Be promoted as a master, The other is still a slave. • Always one master • The former master joins as a slave. <Master in unknown state> 1. The remaining one slave is elected as the leader 2. The leader is promoted as a master. • Algorithms such as Paxos and Raft are used. MasterSlave
- 17. 26 Clustering #3 Sharding • Divide data between nodes and operates as one DB. • Dispatches queries to relevant nodes. • Basically no availability. • Problems with the transaction. • For rather scalability than availability. Coordinator
- 18. 27 3. How to Run your on Kubernetes
- 19. 28 Implemetation Overview : on Kubernetes # Category OSS used Description ⅰ HA • Use Rook/Ceph as Shared Storage. ⅱ • Use LINSTOR/DRBD as Shared Storage. ⅲ Replication • Use Streaming Replication, without Shared Storage. ⅳ Operator • Building and Operating Replication automatically. • We can see following four patterns.
- 20. 29 • K8s manages everything(DB,storage) • Shared-Storage: Ceph • Fenced by kube-fencing < Disadvantage > • Complicated • Insufficient IO HA (i)： Replicas:1 • is deployed as StatefulSet using Rook/Ceph. kube-fencing
- 21. 30 Note: Without Fencing Replicas:1 • When a node goes down, never failover. • To avoid network partition. • It is by design.
- 22. 31 Note: What is • Rook is Kubernetes Operator managing Ceph or others. operator agent/discover agent/discover agent/discover osd osd osd mon mon mon CSI csi-provisioner csi-rbdplugin csi-rbdplugin csi-rbdplugin Rook • Rook makes easy to build Ceph cluster. • Also easy to deploy CSI modules. • CSI: Containar Storage Interface
- 23. 32 HA (ii)： Replicas:1 kube-fencing • LINSTOR is Software-Defined Storage based on DRBD. • K8s manages everything(DB,storage) • Redundancy: DRBD • Simple, Read IO without Network < Disadvantage > • Limited to Scale
- 24. 33 Benchmark Results Single(with EBS) Rook/Ceph DRBD 1nodes 5nodes 2nodes 100 37.8 77.1 • Measured by pgbench for 3 patterns. TPS
- 25. 34 Replication : proxy proxy proxy keeper keeper keeper sentinel sentinel sentinel • Builds Streaming Replication on top of Kubernetes. • 3 types of processes have different roles • Without Shared- Resources < Disadvantage > • Not builtin Read Off- loading
- 26. 36 Operator : • KubeDB operates not only but also others. kubedb-operator -0 -1 -2 postgres snapshotdormantdabases • Database Operator for – PostgreSQL – MySQL – Redis • Kubedb-operator builds SR. • Able to get/restore snapshot easily.
- 27. 37 Example : PostgreSQL Configration by KubeDB apiVersion: kubedb.com/v1alpha1 kind: Postgres metadata: name: ha-postgres namespace: demo spec: version: “10.6-v2" replicas: 3 storageType: Durable storage: storageClassName: "standard" accessModes: - ReadWriteOnce resources: requests: storage: 100Gi spec.version – Choose PostgreSQL version. spec.replicas – The number of Instances. spec.storage – Define storage type/size, etc. • Allows to define Streaming Replication with a simple YAML.
- 28. 38 Example : Snapshot by KubeDB apiVersion: kubedb.com/v1alpha1 kind: Snapshot metadata: name: snapshot-to-s3 labels: kubedb.com/kind: Postgres spec: databaseName: ha-postgres storageSecretName: s3-secret s3: endpoint: 's3.amazonaws.com' bucket: kubedb-qa prefix: demo • Write declarative Snapshot settings by YAML. • Simple backup that applies only this YAML. • You can select storage, – S3 – Swift – Kubernetes Persistent Volume
- 29. 39 Note : Backup with PostgreSQL + Ceph $ kubectl exec -it -n rook-ceph rook-ceph-tools-seq -- rbd -p replicapool ls pvc-bdbc6e53-f6e9-11e8-b0d9-02f062df6b48 $ kubectl exec -it pg-rook-sf-0 -- psql -h localhost -U postgres -c "SELECT pg_start_backup(now()::text);" pg_start_backup ----------------- 0/C000028 (1 row) $ kubectl exec -it -n rook-ceph rook-ceph-tools-seq -- rbd snap create replicapool/img@snap $ kubectl exec -it pg-rook-sf-0 -- psql -h localhost -U postgres -c "SELECT pg_stop_backup();" NOTICE: pg_stop_backup complete, all required WAL segments have been archived pg_stop_backup ---------------- 0/D000050 (1 row) • Need to know PostgreSQL & Ceph Commands.
- 30. 41 4. Kubernetes becomes The Platform
- 31. 42 To Recap The components of database clustering with Kubernetes Native are already available. You can see some operators for DBA task automation. However, it is not over yet. Cloud Native Storage ＋ ＋ ＝ ???
- 32. 43 The Signs I. Pluggable Storage Optimized Storage system for DB on K8s? II. Forked and Cloud-Oriented PostgreSQL AWS Aurora, Azure Hyperscale
- 33. 44 THE LOG IS THE DATABASE. SQL Transactions Caching Storage Logging Storage Logging Storage Logging CPU Memory Cache(SSD) Page Cache(SSD) Log AWS Aurora(PostgreSQL) Azure Hyperscale • Both divide RDBMS functions and are extended by each cloud.
- 34. 45 As the platform for PostgreSQL as a Service DBaaS by Kubernetes STaaS by Kubernetes What we got for DBaaS • HA • Streaming Replication • DB Operator Also for STaaS • Simple Redundancy • Distributed Storage • Interoperable IF(CSI) • Kubernetes will be "The Platform for Platforms."
- 36. 47 Appendix