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Elastic Container Instance:Terms

Last Updated:Jul 08, 2022

This topic describes the terms of Elastic Container Instance for you to understand the service before you use it.

Terms of Elastic Container Instance

The following table describes the terms of Elastic Container Instance.

Term

Description

container

A lightweight, executable, and standalone software package. A container is the running entity of an image.

container group

A set of containers that can be scheduled to the same host. The lifecycle of a container group is determined based on all containers in the group. These containers share the network and storage resources of the container group.

A container group is an elastic container instance and is similar to a pod in Kubernetes.

image

A file system that contains programs, library files, and configurations required by containerized applications. Docker images are the standard packaging format of a containerized application. When you deploy a containerized application, you can specify an image from Docker Hub, Alibaba Cloud Container Registry, or your private image repository.

image cache

A feature that is used to accelerate image pulls and reduce the startup time of an elastic container instance. Image pulls are the main time-consuming operation during instance startup due to factors such as network conditions or the image size. You can accelerate the image pull process by caching images in advance.

volume

A shared storage resource of a container group. You can mount external volumes to a container group. Volumes that are declared in a container group are shared by all containers in the container group.

tag

A key-value pair that is added to a container group. Tags can be added only when you create a container group. Up to 10 tags can be added to a single container group. Each tag key must be unique.

Tags in Elastic Container Instance are similar to labels in Kubernetes.

virtual node

A name that is defined on a local instance to identify a particular remote instance. By using Virtual Kubelet that is provided by the Kubernetes community to deploy virtual nodes to Kubernetes clusters, you can connect Elastic Container Instance to Kubernetes. Elastic container instances do not run on a centralized real node. The instances are broken apart across the global Alibaba Cloud resource pool.

Terms of Kubernetes

Before you use Kubernetes to manage your elastic container instances, you must understand the terms used in Kubernetes. The following table describes the terms.

Term

Description

master

The control node in a Kubernetes cluster. This node is used to manage and schedule the whole cluster.

node

A worker node in a Kubernetes cluster. Workloads run on nodes. If a node breaks down, workloads on the node are transferred to another node by the master.

pod

The smallest unit that is created or deployed in Kubernetes. A pod represents a running process in a cluster and encapsulates one or more closely-related containers.

Deployment

A stateless workload. A Deployment is a layer of abstraction that is higher than the layer of pod. A Deployment defines the information such as the number of replicas and versions of a set of pods.

StatefulSet

A stateful workload. Similar to a Deployment, a StatefulSet is used to manage a group of pods. Unlike a Depoyment, a StatefulSet can provide persistent storage and persistent identifiers for these pods.

Service

An abstract way to expose an application running on a set of pods as a network service. Services are used to provide a unified and stable access address for a set of pods.

ConfigMap

An API object that is used to store non-confidential data in key-value pairs. ConfigMap can be used to store a single attribute and configuration files.

namespace

The logic isolation used in a cluster to group and manage resource objects.

label

A key-value pair that can be added to resource objects. You can add one or more labels to a specific object to manage resources by group in multiple dimensions.

volume

The file directory that can be accessed by multiple containers on a pod. A volume can be mounted to the specified paths of one or more containers on a pod.

PersistentVolume

A volume that is configured by the administrator in a cluster.

PersistentVolumeClaim

A request for storage by a user.

For more information, see Kubernetes Documentation.