Orchestrating Redis & K8s Operators

Agenda
● Redis Labs intro and architecture
● Double orchestration
● Our kubernetes solution
● The way to operators
● Operators intro
● Operators development
● Demo

Introduction to Redis Enterprise
Open source. The leading in-memory database platform,
supporting any high performance operational, analytics or
hybrid use case.
The open source home and commercial provider of Redis
Enterprise (Redise
) technology, platform, products & services.

Redise
- Open Source & Proprietary Technology
Redise
Node
Cluster Manager
Redise
Cluster
• Shared nothing, symmetrical cluster
architecture
• Fully compatible with open source
commands & data structures
Enterprise Layer
Open Source Layer
REST API
Zero latency proxy

• Faster time to market with continuity between
dev/test and production environments that use
Redise
Pack
• Highly available, easier to scale, simpler to manage
Redis technology, integrated with orchestration tools
such as PCF, Kubernetes, Mesosphere...
• Node in a container approach — All Redise
services
inside each container.
Run Redise
clusters on single or multiple nodes
Redise
in Containers

Node in a Pod Approach
Node 1
Vs
Node 2 Node 3 Node 1 Node 2 Node 3
One pod, multiple services per nodeMultiple pods, multiple services per node

Double Orchestration
For fun and profit!
10

What’s Double Orchestration ?
Kubernetes PKS
External
Redis Cluster
Orchestration
Node 1
Redis Shards
Node 2 Node N
Internal

Why like this?
• Resource management - Orchestration platforms are
designed to be generic.
• Again - Performance is king.
• Last but not least, it allows us to maintain a common
architecture - regardless of running environment, be it bare
metal, VM, K8s, Pivotal Cloud Foundry.
(.… Surprisingly enough, not everybody in the world uses containers…)

Who Does What
• Node auto-healing
• Node scaling
• Failover & scaling
• Configuration & monitoring
• Service discovery
• Upgrade
+

And specifically on Kubernetes
Node in a
Pod
Statefulset
Persistent
Volumes
Custom
Controller
Services
Manager

StatefulSet
Our cluster nodes are deployed as part of a statefulset
Affinity
Allows us to control the Redislabs cluster nodes topology
Redislabs Service Manager
Create/Update/Delete service entries for each Redis DB hosted on the cluster
RBAC
The Service Manager must have permissions to access the namespace to create services
Ingress
Allow access to Redis DBs from outside of the k8s cluster
17
Redis Labs on Kubernetes - Building Blocks

StatefulSet
• Introduced in 1.5, GAed in 1.9
• Statefulset Pod consistency
– Pod naming
– Scale-out/Scale-in
– Pod Upgrade
• Persistent Disks
– Same PVC will be used when Pod is (re)scheduled
• All Pods are uniform
• Recovery from error state
pod-0 pod-1 pod-2
PV PV PV

Pod features
• Anti-affinity
– Allows us to control where the pods are being scheduled
• Readiness Probes
– Allows us to control the action flows to avoid data loss
• Pre-stop hook
– Drain the node and move resources to a different node

Why?
• Redis Enterprise is a multi-tenant Redis cluster
• Redis Enterprise Database can have 1 or more network endpoints
Problem
• Expose databases as a service instance
Solution
• Python based application that will: create, delete or update necessary database
service entries
• Based on an idempotent reconciliation loop
Redis Enterprise Services Manager

Kubernetes Cluster
Redis Labs Stateful Set
Worker Node
pod-0
Worker Node
pod-2
Worker Node
pod-1
Redis Enterprise Cluster
PV PV PV
K8s API
Services
Manager
Add/Edit/Delete
Database Services
App App App

• Provide a solid primary db solution for end-users
• Stateful application
– Some changes cannot be performed
– Some changes need to mutate the state before applying the actual change
– Data-loss is unacceptable
• Support multiple k8s deployments
– Cloud: GKE, AWS, etc
– Openshift
– PKS
– Vanilla
– On-prem hardware vendor
• Ingress
• Packaging
Redis Labs Challenges

• Started out with 9 static yaml files
– Hard to deploy
– Hard to maintain
– Hard to distribute
– No control over the deployment life-cycle
• Helm
– Customized deployment
– Easier to maintain
– Not fully supported everywhere
– No control over the deployment life-cycle
• Operator
– Simple deployment (2 yaml files)
– Full control over life-cycle
– K8s compatible
Our journey
.yaml
.yaml

26
Custom Resource
+
Custom Controller
=
Operator

27
kubectl
API Server
StatefulSet Controller
Watch(StatefulSet)
pod-0 pod-1 pod-2
my-sts
kubectl create -f my-sts.yaml
PV PV PV

28
kubectl
StatefulSet Controller
Watch(StatefulSet)
pod-0 pod-1 pod-2
my-sts
kubectl scale statefulset my-sts --replicas=5
pod-3 pod-4
API Server

29
kubectl
API Server
RedisCluster Controller
Watch(RedisCluster)
my-redis-cluster
kubectl create -f my-redis-cluster.yaml
Stateful
Set
UI
service
Service
Account
...

30
kubectl
API Server
RedisCluster Controller
Watch(RedisCluster)
my-redis-cluster
kubectl apply -f my-redis-cluster.yaml
Stateful
Set
UI
service
Service
Account
...
get-status()
example: downscale

● Life Cycle Control
○ Scale Up → Add new pod, Rebalance Data
○ Healing → Restore Backups, Auto Recovery
○ Backup
○ Validations (ex. even # pods)
● Configuration
○ Automate complex deployments (ex. Vault cluster and etcd cluster)
○ Reconfiguration
○ Agnostic configuration (ex. PVC by cloud provider)
● 3rd party resource (ex. prometheus)
● Cross distribution
● Easy to deploy
Why are operators useful?

32
Our Upgrade Flow
In a Redis Enterprise Cluster we need to:
1. Drain pod
2. Stop pod
3. Start new pod
● Downgrade - not supported (oss backward compatibility)

Our Upgrade Flow
With Yaml/Helm -
We used a life cycle preStop hook of a stateful set
1. Encoded inside the yaml - cumbersome
2. Cannot validate version
3. No error handling
With Operator -
1. Maintain logic in code not in a config file
2. Validations: not a downgrade, cluster is not already in an upgrade process
3. Error handling
4. Manage canary deployment

37
affinity:
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
labelSelector:
matchExpressions:
key: app
operator: In
values:
{{ template "redisenterprise.name" . }}
key: release
operator: In
values:
{{ .Release.Name }}
key: redis.io/role
operator: In
values:
node
topologyKey: kubernetes.io/hostname
terminationGracePeriodSeconds: 31536000
serviceAccountName: {{ template "redisenterprise.serviceAccountName" . }}
{{ with .Values.imagePullSecrets }}
imagePullSecrets:
{{ toYaml . | indent 8 }}
{{ end }}
containers:
name: redis
image: {{ .Values.redisImage.repository }}:{{ .Values.redisImage.tag }}
imagePullPolicy: {{ .Values.redisImage.pullPolicy }}
readinessProbe:
exec:
command:
# check that the node is bootstrapped and that its connected and synced.
bash
c
curl silent localhost:8080/v1/bootstrap && /opt/redislabs/bin/rladmin status
nodes | grep node:$(cat /etc/opt/redislabs/node.id) | grep OK
initialDelaySeconds: 20
timeoutSeconds: 5
lifecycle:
preStop:
exec:
command:
# enslave the node, if this current node is master, change the master to
the first slave node.
bash
c
/opt/redislabs/bin/rladmin node $(cat /etc/opt/redislabs/node.id) enslave
&& ((/opt/redislabs/bin/rladmin status nodes | grep node:$(cat
/etc/opt/redislabs/node.id) | grep q master) && /opt/redislabs/bin/rlutil
change_master master=$(/opt/redislabs/bin/rladmin status nodes | grep slave |
head 1 | cut d " " f 1| cut d ":" f2) && sleep 10) || /bin/true
resources:
{{ toYaml .Values.redisResources | indent 10 }}
ports:
containerPort: 8001
containerPort: 8443
containerPort: 9443
securityContext:
capabilities:
add:
SYS_RESOURCE
{{ if .Values.persistentVolume.enabled }}
volumeMounts:
mountPath: "/opt/persistent"
name: redisstorage
{{ end }}
env:
name: K8S_ORCHASTRATED_DEPLOYMENT
value: "yes"
name: JOIN_HOSTNAME
value: {{ template "redisenterprise.fullname" . }}
name: PERSISTANCE_PATH
value: /opt/persistent
{{ end }}
name: K8S_SERVICE_NAME
value: {{ template "redisenterprise.fullname" . }}
name: BOOTSTRAP_HANDLE_REDIRECTS
value: "enabled"
name: BOOTSTRAP_CLUSTER_FQDN
value: {{ template "redisenterprise.clusterDNS" . }}
name: BOOTSTRAP_DMC_THREADS
value: "10"
name: BOOTSTRAP_USERNAME
valueFrom:
secretKeyRef:
name: {{ template "redisenterprise.fullname" . }}
key: username
name: BOOTSTRAP_PASSWORD
valueFrom:
secretKeyRef:
key: password
name: BOOTSTRAP_LICENSE
valueFrom:
secretKeyRef:
key: license
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
name: {{ template "redisenterprise.statefulsetName" . }}
labels:
app: {{ template "redisenterprise.name" . }}
chart: {{ template "redisenterprise.chart" . }}
release: {{ .Release.Name }}
heritage: {{ .Release.Service }}
spec:
volumeClaimTemplates:
metadata:
name: redisstorage
labels:
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: {{ .Values.persistentVolume.size | quote }}
{{ if .Values.persistentVolume.storageClass }}
{{ if (eq "" .Values.persistentVolume.storageClass) }}
storageClassName: ""
{{ else }}
storageClassName: "{{ .Values.persistentVolume.storageClass }}"
{{ end }}
{{ end }}
{{ end }}
serviceName: {{ template "redisenterprise.fullname" . }}
replicas: {{ .Values.replicas }}
updateStrategy:
type: "RollingUpdate"
template:
metadata:
labels:
redis.io/role: node
spec:
{{ with .Values.nodeSelector }}
nodeSelector:
{{ toYaml . | indent 8 }}
{{ end }}

38
kubectl create -f cr.yaml
cr.yaml
"apiVersion": "app.redislabs.com/v1alpha1",
"items": [
{
"apiVersion": "app.redislabs.com/v1alpha1",
"kind": "RedisEnterpriseCluster",
"metadata": {
...
"creationTimestamp": "2018-07-12T15:47:31Z",
"generation": 0,
"name": " my-cluster-test",
"namespace": "redis"
},
"spec": {
"nodes": 3,
"serviceAccountName": "my-cluster-test",
"uiServiceType": "ClusterIP",
"username": " demo@redislabs.com "
...
curl http://127.0.0.1:8001/apis/app.redislabs.com/v1alpha1/
redisenterpriseclusters

• Started by CoreOS
– CoreOS pioneered by creating a few Operators (Prometheus & vault)
• Operator SDK:
minimize boilerplate and help developers to get started writing Operators
• The Basic API:
– Register Watchers on any Resource
– Create/Read/Update/Delete/Get on any resource
– Register schemas using k8s GO api
• Operator Lifecycle Manager

41
The Reconciliation/Control Loop
• Called for every update, delete or creation on the watched resources
– No way of knowing what type of event except Delete
• Called every X seconds to “resync” resources
• Our responsibility is to allow the user to use our resource as any other in k8s
– AKA idempotent API
• Every call to handle we get our watched resources, we need to determine what to
do exactly

42
Idempotent APIs
Desired State = Current Resource Current State
• Aggregation of deployed
resources
• Internal application
state

43
The Reconciliation/Control Loop - Challenges
• Determine which changes need to happen
• Determine if the change is valid
• K8s doesn’t provide a solid validation before applying changes to CR
– 1.9 has a beta feature for OpenAPI validations
• Long running processes as part of a resource change

Pending
Creation
Running
Invalid
Error
create
create
apply
create
apply
apply
Pending Creation - initial state where cluster is not deployed yet
Running - Cluster Deployed and is either running or starting to run and not ready yet
Invalid - Invalid configuration was requested. E.g. even #nodes. Until a valid configuration is applied the status will remain invalid
Error - Error when trying to deploy or update the Redis Enterprise Cluster
apply
Redis Cluster Status
applyapply
create = kubectl create -f cr.yaml
apply = kubectl apply -f cr.yaml

45
Development Challenges
• Deep understanding of how Kubernetes works (statefulsets, controller, APIs)
• Workflows - Idempotent APIs are challenging due to state mutation
• Double Orchestration - Adds a level of complexity compared to stateless
deployments
• Various SDK issues

https://www.telepresence.io
46
One Last Thing

Orchestrating Redis & K8s Operators

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