Container Service for Kubernetes:Overview of Elastic Container Instance

Specifications

The specifications include vCPUs and memory configurations that determine the computing performance of pods. When you create a pod, you can specify the number of vCPUs and memory size, or specify an Elastic Compute Service (ECS) instance type to meet special requirements, such as the requirements for GPUs and local disks. Different billing methods apply to these specification types. For more information, see Billing of elastic container instances.

Resources in Elastic Container Instance can be created in different ways. Select a method based on your business requirements. For more information, see Create an elastic container instance.

Images

A pod can contain up to 20 containers. Before you deploy a container application, you must prepare a container image. A container image contains the programs, library files, and configurations that are required to run containerized applications. Before you pull images, make sure that the network is accessible. We recommend that you use ImageCache to accelerate the startup and pod creation.

• Pull images

  When an elastic container instance starts, its containerd pulls container images from a remote image repository. To pull public images, make sure that the elastic container instance has Internet access. You can configure a public Network Address Translation (NAT) gateway for the virtual private cloud (VPC) where the elastic container instance is deployed. Additionally, you can associate an elastic IP address (EIP) with the elastic container instance to pull public images.

  We recommend that you store container images in Container Registry to pull images more rapidly through a VPC. In addition, You can pull private images from Container Registry without a Secret. This ensures high efficiency for image pulling. For more information, see Pull images from a Container Registry instance without using a Secret and Use managed-aliyun-acr-credential-helper to pull images without using a secret.

• Image cache

  Elastic Container Instance provides an image cache feature that allows you to create a cache snapshot from an image. This cache snapshot can be used to create an elastic container instance, eliminating or reducing the need to download image layers and therefore accelerating the creation process. By default, ACK Serverless clusters are deployed with ImageCache CustomResourceDefinition (CRD) to enable this feature. For more information, see Use ImageCache to accelerate the creation of elastic container instances.

Storage

• Temporary storage

  By default, a pod is allocated 30 GiB of free memory for temporary storage, which is occupied by the container image to start the elastic container instance. You can increase the memory size for temporary storage based on your business requirements. For more information, see Scale up the temporary storage space.

• Persistent storage

  You can share or retain the stored files by mounting volumes to elastic container instances. In ACK Serverless clusters, use the CSI plug-in to mount Alibaba Cloud storage volumes, such as disks,File Storage NAS (NAS) file systems, and Object Storage Service (OSS) buckets. For more information, see CSI overview.

Networks

• Private IP address

  A pod uses an elastic network interface (ENI) of a vSwitch in the VPC to which the pod belongs. When you create a pod, a private IP address is randomly assigned from the appropriate vSwitch. The vSwitch is selected based on the k8s.aliyun.com/eci-vswitch field in pod annotations, followed by PodNetworking and eci-profile configurations in that order. For more information about how to specify a private IP address or use a fixed one, see Specify a private IP address for a pod and Configure a fixed IP address for a pod.

• Internet access

  By default, a pod is assigned an internal IP address. If a pod needs to access the Internet, for example, to pull public images, you must associate an elastic IP address (EIP) with the pod, or associate a network address translation (NAT) gateway with the VPC to which the pod belongs. For more information, see Enable Internet access for pods.

• IPv6 address

  Elastic Container Instance supports IPv6 addresses, offering a larger pool of available IP addresses compared to IPv4. For more information, see Assign an IPv6 address to an Elastic Container Instance-based pod.

Containers

You can configure container startup commands, liveness and readiness probes, and security contexts for a pod to use predefined arguments, similar to how it is done in Kubernetes. For more information about container configurations in elastic container instances, see Container configurations.

Data cache

This feature allows you to create a cache of a large amount of business data, such as model training data. When you create an elastic container instance, you can mount and use the cached data. This reduces the startup time of the instance and prevents repeated data downloads, reduceing the costs of using the instance. For more information, see Data cache overview.

ECI pod annotation

When you schedule pods of a Kubernetes cluster to run on an elastic container instance, you can add annotations to the pods to make full use of the features of Elastic Container Instance. Make sure that the annotations comply with Kubernetes syntax. For more information about annotations supported by Elastic Container Instance, see ECI pod annotation.