Configure an ECI pod to use a fixed IP address - Elastic Container Instance

Some applications require a pod to maintain a consistent IP address. This topic describes how to configure an Elastic Container Instance (ECI) pod to use a fixed IP address.

How it works

By default, when you create an ECI pod, the system assigns a random IP address to the pod from the CIDR block of the vSwitch specified in the eci-profile. When a pod is released due to a failure, the system releases its IP address and assigns a new one to the replacement pod. In certain scenarios, such as when a service is exposed directly by its IP address, a pod may require a fixed IP address to ensure business continuity.

To address these scenarios, ECI provides the fixed IP address feature. When you create an ECI pod with this feature enabled, the system allocates two IP addresses from the configured vSwitch: a dynamic IP address, which is not visible within the cluster, and a fixed IP address. After the pod is released, the system retains its fixed IP address for a specific period, which is 48 hours by default. If a new pod is created within this retention period that has the same cluster ID, namespace, and pod name as the released pod, and also has the fixed IP address feature enabled, the system assigns the retained IP address to the new pod. This ensures the pod's IP address remains consistent.

Note

In this scenario, you can use a StatefulSet to deploy your application. When a pod in a StatefulSet is released, the system automatically creates a new pod with the same namespace and pod name.

Configuration

Add annotations to the pod metadata to enable the fixed IP address feature and to configure the retention period of the fixed IP address. The following table describes the annotations.

Annotation

Example

Description

k8s.aliyun.com/eci-fixed-ip

"true"

Set to "true" to enable the fixed IP address feature.

k8s.aliyun.com/eci-fixed-ip-retain-hour

"24"

The number of hours to retain the fixed IP address after the pod is released.

If omitted, the default is 48 hours.

Procedure

Create a Service and a StatefulSet.

kubectl apply -f fixedIp.yaml

The following fixedIp.yaml file defines a Service and a StatefulSet. The StatefulSet includes an ECI pod with the annotation that enables the fixed IP address feature.

apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  selector:
    matchLabels:
      app: nginx
  serviceName: "nginx"
  minReadySeconds: 10
  template:
    metadata:
      annotations:
        k8s.aliyun.com/eci-fixed-ip: "true"  # Enable the fixed IP address feature.
      labels:
        app: nginx
        alibabacloud.com/eci: "true"
    spec:
      containers:
      - name: nginx
        image: registry-vpc.cn-beijing.aliyuncs.com/eci_open/nginx:1.14.2
        ports:
        - containerPort: 80
          name: web

Run the following command to monitor pod status changes.

kubectl get pod -o wide -w

The output shows that the StatefulSet created a pod named web-0 with the IP address 172.16.0.129.

d:~$ kubectl get pod -o wide -w
NAME    READY   STATUS              RESTARTS   AGE   IP              NODE                         NOMINATED NODE   READINESS GATES
web-0   0/1     Pending             0                9s    <none>          <none>                       <none>           <none>
web-0   0/1     Pending             0               20s    <none>          <none>                       <none>           <none>
web-0   0/1     Pending             0               20s    <none>          virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     Pending             0               20s    <none>          virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     ContainerCreating   0               69s    172.16.0.129   virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   1/1     Running             0               76s    172.16.0.129   virtual-kubelet-cn-beijing-h   <none>           <none>

Open a new terminal to connect to the cluster and run the following command to delete the pod in the StatefulSet.
```
kubectl delete pod web-0
```

Switch back to the first terminal and continue to observe the pod status changes.

The output shows that after the original pod is deleted, the StatefulSet automatically creates a new pod that reuses the original IP address.

Note

The creation of the new pod may be delayed because the IP address remains occupied until the previous pod is completely deleted.

1:~$ kubectl get pod -o wide -w
NAME    READY   STATUS              RESTARTS   AGE     IP              NODE                          NOMINATED NODE   READINESS GATES
web-0   0/1     Pending             0          9s      <none>          <none>                        <none>           <none>
web-0   0/1     Pending             0          20s     <none>          <none>                        <none>           <none>
web-0   0/1     Pending             0          20s     <none>          virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     Pending             0          20s     <none>          virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     ContainerCreating   0          69s     172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   1/1     Running             0          76s     172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   1/1     Terminating         0          2m37s   172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     Terminating         0          2m39s   172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     Terminating         0          2m55s   172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     Terminating         0          2m55s   172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     Pending             0          0s      <none>                                        <none>           <none>
web-0   0/1     Pending             0          0s      <none>                                        <none>           <none>
web-0   0/1     Pending             0          1s      <none>                                        <none>           <none>
web-0   0/1     Pending             0          1s      <none>                                        <none>           <none>
web-0   0/1     Pending             0          17s     <none>                                        <none>           <none>
web-0   0/1     Pending             0          17s     <none>          virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     Pending             0          17s     <none>          virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   0/1     ContainerCreating   0          69s     172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>
web-0   1/1     Running             0          76s     172.16.0.129    virtual-kubelet-cn-beijing-h   <none>           <none>