SocketCluster
Kubernetes - Use initContainer instead of another container as source volume
It's better doing it that way because it's not necessary to wait for the files to become available (as seen here: https://github.com/SocketCluster/socketcluster/blob/5226c2a/sample/dockerwait.js).
Example of how it would work:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: my-project-scc
spec:
replicas: 2
revisionHistoryLimit: 2
template:
metadata:
labels:
app: my-project-scc
spec:
initContainers:
- name: src-container
image: myuser/sourceimage
command:
- cp
- '-a'
- /usr/src/.
- /usr/dest/
volumeMounts:
- mountPath: /usr/dest
name: src-volume
resources:
limits:
cpu: 10m
memory: 50Mi
requests:
cpu: 10m
memory: 50Mi
containers:
- name: socketcluster
image: 'socketcluster/socketcluster:v14.3.0'
ports:
- containerPort: 8000
env:
- name: SCC_STATE_SERVER_HOST
value: my-project-scc-state
- name: SCC_INSTANCE_IP
valueFrom:
fieldRef:
fieldPath: status.podIP
- name: SOCKETCLUSTER_WORKER_CONTROLLER
value: /usr/src/app/worker.js
- name: SOCKETCLUSTER_MASTER_CONTROLLER
value: /usr/src/app/server.js
# ... other envs
resources:
limits:
cpu: 100m
memory: 360Mi
requests:
cpu: 100m
memory: 360Mi
livenessProbe:
httpGet:
path: /health-check
port: 8000
initialDelaySeconds: 300
timeoutSeconds: 5
volumeMounts:
- mountPath: /usr/src/app
name: src-volume
affinity:
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: app
operator: In
values:
- my-project-scc
topologyKey: kubernetes.io/hostname
volumes:
- name: src-volume
emptyDir: {}
The container is only started when the init container has finished. I was using that until recently, having both as normal containers can cause some problems, and having to set the wait timeout to bigger values each time newer dependencies are added.
Recently I've ditched this deployment in favor of building my own socketcluster image with the correct dependencies already installed, since copying node_modules from the image to the volume was taking too long (almost 20 mins). But it's here as a suggestion.
@JCMais I finally got some time to test your approach on GKE and it worked perfectly and it's definitely much cleaner so I'll try to push with an update soon.
Yea, I need to start using initContainer. I haven't started using it yet. I was going to on my next project. Thanks for the example!
