This topic describes the terms that are used in Serverless App Engine (SAE).
namespace
A namespace is a logically isolated runtime environment.
Namespaces can be categorized into two types: Kubernetes namespace and microservices namespace. Namespaces isolate different runtime environments, such as development, test, and production environments, based on the service calling and distributed configuration pushing of applications.
application
An application is a basic management unit in SAE.
In most cases, an application contains one or more instances. SAE allows you to manage the lifecycle of applications. You can create, deploy, start, roll back, scale out or in, stop, and delete applications in SAE.
application instance
An application instance is the minimum unit on which an application runs.
In most cases, an application runs on one or more instances and can have multiple deployment versions. Different versions of the application can run on different instances.
microservices application
SAE provides microservices-related capabilities such as 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
Startup commands are used to start and run containers.
When you start a container, the main process starts. Before you can start the main process, you must configure and initialize a MySQL database. Configure the ENTRYPOINT or CMD parameter in the Dockerfile file when you create an image. For example, if you specify ENTRYPOINT ["top", "-b"] in the Dockerfile file, SAE automatically executes the command at the startup of the container.
application health check
SAE performs scheduled health checks on application instances during the runtime of an application.
SAE provides the following methods to perform application health checks:
SAE uses a liveness probe to check whether an application instance is running as expected. If the application instance is not running as expected, SAE restarts the application instance.
SAE uses a readiness probe to check whether an application instance is ready to process requests. If the check fails, the application instance is not ready and SAE blocks access to the application instance. If the check is successful, the application instance is ready and SAE allows access to the application instance.
Application Configuration Management
Application Configuration Management is a distributed architecture-based tool that allows you to manage and push application configurations in a centralized manner.
In SAE, you can use Application Configuration Management to manage and push application configurations in a centralized manner. You can also isolate and synchronize configurations between different environments by using namespaces.
container
A container is the running entity of an image.
You can create, start, stop, delete, or suspend a container. The relationship between images and containers is similar to the relationship between classes and instances in object-oriented programming. Images are static whereas containers are dynamic. Instances and containers are in one-to-one mapping relationships.
container image
A container image is a standard form of an application package. You can use a Dockerfile to package an application and the environments on which the application depends to a container image, push the container image to an image repository, pull the container image in a test or production environment, and then start containers.
EDAS Container
Enterprise Distributed Application Service (EDAS) Container is developed by using the High-speed Service Framework (HSF) architecture and is used to run applications. EDAS Container includes Ali-Tomcat and Pandora containers.
In addition to microservices frameworks such as Spring Cloud and Dubbo, SAE supports Alibaba Cloud HSF.