Serverless App Engine (SAE) uses the following terms throughout its documentation and console.
Namespace
A namespace is a logically isolated runtime environment. SAE supports two types of namespaces: Kubernetes namespaces and microservices namespaces. Namespaces isolate environments—such as development, test, and production—by separating service calls and distributed configuration pushes between applications.
Use namespaces when you need to separate workloads across environments or teams. For small, single-team projects, a single namespace is sufficient.
Application
An application is the basic management unit in SAE. Each application contains one or more instances. SAE lets you manage the full lifecycle of an application: create, deploy, start, roll back, scale out or in, stop, and delete.
Application instance
An application instance is the minimum unit on which an application runs. An application can run across one or more instances and support multiple deployment versions, with different versions running on different instances.
Microservices application
SAE provides microservices capabilities including service registration and discovery, and service governance. You can develop applications and perform inter-service communication based on microservices frameworks such as Spring Cloud, Dubbo, Motan, Service Mesh, and Kubernetes Service. For more information, see Concepts and capabilities related to SAE microservices.
Startup command
A startup command starts and runs a container's main process. Before you can start the main process, you must configure and initialize a MySQL database. Configure the ENTRYPOINT or CMD instruction in a Dockerfile to define what runs at container startup. For example, specifying ENTRYPOINT ["top", "-b"] in the Dockerfile causes SAE to run that command automatically when the container starts.
Application health check
SAE runs scheduled health checks on application instances throughout an application's runtime. Health checks help SAE decide whether to restart an instance or stop routing traffic to it, keeping your application available and responsive.
SAE supports two types of probes:
Liveness probe
A liveness probe checks whether an application instance is running as expected. If the probe fails, SAE restarts the instance.
Readiness probe
A readiness probe checks whether an application instance is ready to handle requests. If the probe fails, SAE blocks access to the application instance. Once the probe succeeds, SAE allows access to the application instance.
Application Configuration Management
Application Configuration Management is a distributed architecture-based tool that lets you manage and push application configurations centrally. Use it to push configurations to multiple applications at once and isolate and synchronize configurations across environments using namespaces.
Container
A container is the running instance of a container image. Containers are dynamic; images are static. Each application instance maps one-to-one to a container. Supported operations include create, start, stop, delete, and suspend.
Container image
A container image is the packaged form of an application. Use a Dockerfile to bundle your application and its dependencies into an image, push the image to an image repository, and pull it into a test or production environment to start containers from it.
EDAS Container
Enterprise Distributed Application Service (EDAS) Container is an Alibaba Cloud container runtime built on the High-speed Service Framework (HSF) architecture. It includes Ali-Tomcat and Pandora containers and is used to run applications. SAE supports Alibaba Cloud HSF in addition to microservices frameworks such as Spring Cloud and Dubbo.