NODE_APP_INSTANCE similar variable inside kubernetes node app

Question

When we use PM2 in cluster mode, we can find out the instance number inside node app using process.env.NODE_APP_INSTANCE, but how we can find that inside a kubernetes cluster without pm2. I'm looking for similar like find replica instance number or etc.

Imagine a node app with 2 or more replicas and we need to run node-cron scheduler only inside one of pods.

did you find any answer?

moein rahimi
– moein rahimi

2022-12-15 23:26:37 +00:00
Commented Dec 15, 2022 at 23:26 — moein rahimi
– moein rahimi, Commented Dec 15, 2022 at 23:26
@moeinrahimi Yes, I've added the answer.

Vahid Alimohamadi
– Vahid Alimohamadi

2022-12-20 11:59:47 +00:00
Commented Dec 20, 2022 at 11:59 — Vahid Alimohamadi
– Vahid Alimohamadi, Commented Dec 20, 2022 at 11:59

Vahid Alimohamadi · Accepted Answer · 2022-12-20 11:59:10Z

1

I found that when use Statefulset instead of the Deployment then it's possible to inject the determinable POD name as an environment variable.

  ...
  containers:
     ...
     env:
     - name: "POD_NAME"
       valueFrom:
         fieldRef:
           fieldPath: metadata.name

And then POD_NAME variable has the value like this: pod-0 or pod-1 and so on. So we can find out the instance number with that ordinal number.

answered Dec 20, 2022 at 11:59

Vahid Alimohamadi

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