Deployment¶
Create a deployment to govern the lifecycle and orchestration of a set of identical pods.
Automatic pod selection¶
When you specify pods in a deployment, you normally have to configure the appropriate labels and selectors to make the deployment control the relevant pods. This construct does this automatically.
import * as kplus from 'cdk8s-plus-29';
import { Construct } from 'constructs';
import { App, Chart, ChartProps } from 'cdk8s';
export class MyChart extends Chart {
constructor(scope: Construct, id: string, props: ChartProps = { }) {
super(scope, id, props);
new kplus.Deployment(this, 'FrontEnds', {
containers: [ { image: 'node' } ],
});
}
}
const app = new App();
new MyChart(app, 'deployment');
app.synth();
Note the resulting manifest contains a special cdk8s.io/metadata.addr
label that is applied to the pods, and is used as
the selector for the deployment.
apiVersion: apps/v1
kind: Deployment
metadata:
name: deployment-frontends-c8e48310
spec:
minReadySeconds: 0
progressDeadlineSeconds: 600
replicas: 2
selector:
matchLabels:
cdk8s.io/metadata.addr: deployment-FrontEnds-c89e9e97
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
labels:
cdk8s.io/metadata.addr: deployment-FrontEnds-c89e9e97
spec:
automountServiceAccountToken: false
containers:
- image: node
imagePullPolicy: Always
name: main
resources:
limits:
cpu: 1500m
memory: 2048Mi
requests:
cpu: 1000m
memory: 512Mi
securityContext:
allowPrivilegeEscalation: false
privileged: false
readOnlyRootFilesystem: true
runAsGroup: 26000
runAsNonRoot: true
runAsUser: 25000
dnsPolicy: ClusterFirst
restartPolicy: Always
securityContext:
fsGroupChangePolicy: Always
runAsNonRoot: true
setHostnameAsFQDN: false
Exposing via a service¶
Following up on pod selection, you can also easily create a service that will select the pods relevant to the deployment.
// store the deployment to created in a constant
const frontends = new kplus.Deployment(this, 'FrontEnds', {
containers: [ {
image: 'node',
portNumber: 9000,
} ],
});
// create a ClusterIP service that listens on port 9000 and redirects to port 9000 on the containers.
frontends.exposeViaService({ ports: [{
port: 9000,
}]
});
Notice the resulting manifest, will have the same cdk8s.io/metadata.addr
magic label as the selector.
This will cause the service to attach to the pods that were configured as part of the said deployment.
apiVersion: apps/v1
kind: Deployment
metadata:
name: deployment-frontends-c8e48310
spec:
minReadySeconds: 0
progressDeadlineSeconds: 600
replicas: 2
selector:
matchLabels:
cdk8s.io/metadata.addr: deployment-FrontEnds-c89e9e97
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
labels:
cdk8s.io/metadata.addr: deployment-FrontEnds-c89e9e97
spec:
automountServiceAccountToken: false
containers:
- image: node
imagePullPolicy: Always
name: main
ports:
- containerPort: 9000
resources:
limits:
cpu: 1500m
memory: 2048Mi
requests:
cpu: 1000m
memory: 512Mi
securityContext:
allowPrivilegeEscalation: false
privileged: false
readOnlyRootFilesystem: true
runAsGroup: 26000
runAsNonRoot: true
runAsUser: 25000
startupProbe:
failureThreshold: 3
tcpSocket:
port: 9000
dnsPolicy: ClusterFirst
restartPolicy: Always
securityContext:
fsGroupChangePolicy: Always
runAsNonRoot: true
setHostnameAsFQDN: false
---
apiVersion: v1
kind: Service
metadata:
name: deployment-frontends-service-c8206158
spec:
externalIPs: []
ports:
- port: 9000
selector:
cdk8s.io/metadata.addr: deployment-FrontEnds-c89e9e97
type: ClusterIP
Scheduling¶
In addition to the scheduling capabilities provided by pod scheduling, a Deployment offers the following:
Spreading¶
A spread is a separation of pods from themselves. It can be used to ensure replicas of the same workload are scheduled on different topologies.
The same API is also available on all workload resources (i.e
Deployment
,StatefulSet
,Job
,DaemonSet
).
const redis = new kplus.Deployment(this, 'Redis', {
containers: [{ image: 'redis' }],
replicas: 3,
});
redis.scheduling.spread({
topology: kplus.Topology.HOSTNAME
});
This example ensures that each replica of the Redis
deployment
will be scheduled on a different node.
Take, for example, a three-node cluster running a web application with an in-memory cache like redis. You’d like to co-locate the web servers with the cache as much as possible, while still maintaining node failure resistance. (i.e not all pods are on the same node).
Here is how you can accomplish that:
const redis = new kplus.Deployment(this, 'Redis', {
containers: [{ image: 'redis' }],
replicas: 3,
});
const web = new kplus.Deployment(this, 'Web', {
containers: [{ image: 'web' }],
replicas: 3,
});
// ensure redis is spread across all nodes
redis.scheduling.spread({
topology: kplus.Topology.HOSTNAME
});
// ensure web app is spread across all nodes
web.scheduling.spread({
topology: kplus.Topology.HOSTNAME
});
// ensure a web app pod always runs along side a cache instance
web.scheduling.colocate(redis);
Connections¶
See Pod connections.