Is it possible to get k8s pod limits in my application? - node.js

Question

I have an application running a kafka consumer inside a pod with 1.5GB of memory limit.
As you probably know, we need to write some logic to stop the consumer from fetching messages when we are about to reach the memory limit.
I was wondering to stop the consumer when the memory my application is using is above 75% of the memory limit.
So my question is... is it possible to get k8s memory limit runtime? How can I stop my consumer based how much free memory I have?
this.consumer.on('message', (message) => {
checkApplicationMemoryUsage();
executeSomethingWithMessage(message);
});
function checkApplicationMemoryUsage() {
const appMemoryConsumption = process.memoryUsage().heapUsed;
const appMemoryLimit = <?????>;
if (appMemoryConsumption / appMemoryLimit > 0.75) this.consumer.pause();
else this.consumer.resume();
}
The solution I was thinking is to pass the limits as env vars to my pod on the deployment spec, but I wish there was a better way

Answer 1

Yes, the Downward API provides a way to achieve what you need.
apiVersion: v1
kind: Pod
metadata:
name: kubernetes-downwardapi-volume-example-2
spec:
containers:
- name: client-container
image: k8s.gcr.io/busybox:1.24
command: ["sh", "-c"]
args:
- while true; do
echo -en '\n';
if [[ -e /etc/podinfo/cpu_limit ]]; then
echo -en '\n'; cat /etc/podinfo/cpu_limit; fi;
if [[ -e /etc/podinfo/cpu_request ]]; then
echo -en '\n'; cat /etc/podinfo/cpu_request; fi;
if [[ -e /etc/podinfo/mem_limit ]]; then
echo -en '\n'; cat /etc/podinfo/mem_limit; fi;
if [[ -e /etc/podinfo/mem_request ]]; then
echo -en '\n'; cat /etc/podinfo/mem_request; fi;
sleep 5;
done;
resources:
requests:
memory: "32Mi"
cpu: "125m"
limits:
memory: "64Mi"
cpu: "250m"
volumeMounts:
- name: podinfo
mountPath: /etc/podinfo
volumes:
- name: podinfo
downwardAPI:
items:
- path: "cpu_limit"
resourceFieldRef:
containerName: client-container
resource: limits.cpu
divisor: 1m
- path: "cpu_request"
resourceFieldRef:
containerName: client-container
resource: requests.cpu
divisor: 1m
- path: "mem_limit"
resourceFieldRef:
containerName: client-container
resource: limits.memory
divisor: 1Mi
- path: "mem_request"
resourceFieldRef:
containerName: client-container
resource: requests.memory
divisor: 1Mi
See the above example taken from Store Container fields section in K8s docs.