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
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.
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.”
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
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
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
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."