:Deployment environment overview

Web App Service allows you to customize deployment environments When you create application or deployment environments, Web App Service provisions one or more resources to run these applications. These resources are listed as follows.

• Reverse proxy: Web App Service has a built-in reverse proxy. After the reverse proxy is started, it listens on port 80 of ECS instances and relays HTTP requests to applications that run on these ECS instances.
• Virtual Private Cloud (VPC): A Virtual Private Cloud (VPC) is a dedicated private network on the cloud. VPCs allow you to securely route traffic to applications that run on ECS instances in Web App Service. If no VPC is configured when you start a deployment environment, Web App Service uses the default VPC.
• ECS instances: You can run applications for the specified platforms of technology stacks on ECS instances. You must configure settings, such as the instance type, number of instances, security group, key pair, and whether to enable an Internet IP address.
• Server Load Balancer: With traffic distribution, SLB allows you to enhance service capabilities of applications, remove single points of failure, and improve the availability of applications.
• ApsaraDB for RDS instances: Web App Service allows you to orchestrate ApsaraDB for RDS resources. After configuring settings, such as the database type, database version, and storage type, you can add ApsaraDB for RDS instances to your deployment environment.
• Configure a service port: In Web App Service, the service port of an application is open on an ECS instance. After you configure a service port, Web App Service routes requests to the service port of the specified application. This allows clients to access the application.
• Configure health checks: With health checks, Web App Service allows you to check whether the status of running applications is healthy. After you create health checks, Web App Service will perform corresponding operations on applications based on the health check status. For example, Web App Service restarts an ECS instance if a health check for the ECS instance fails. It also restarts an application instance if the health check status of the application instance is abnormal.
• Commands and lifecycle hooks: Web App Service provides features, such as customizing start commands, stop commands, and lifecycle hooks, to extend service capabilities. These features help you change default management tasks to ensure that they can meet your business requirements.
• Environment variables: You can specify a set of environment variables for each application. After you deploy an application, you can use these environment variables to change the application settings. Environment variables specified for each application are exclusive. You can specify the same environment variable for multiple applications but the value of the environment variable can be different for each application.
• Configure parameters for a Java virtual machine: JVM settings are used to configure containers when you start an application. Accurate configuration of these settings helps you reduce the overhead of garbage collection (GC), decrease server response time, and improve overall throughput.