You can configure the PostStart and PreStop lifecycle hooks in the Enterprise Distributed Application Service (EDAS) console so that you can add code to customize some operations when applications are running. You can also configure the Liveness and Readiness probes in the EDAS console to detect the liveness and readiness of containers. This topic describes how to configure the lifecycle hooks of applications and the Liveness and Readiness probes of containers.

Background information

In general, some operations are performed before and after an application is started or stopped. For example, you can deploy resources before you start an application and gracefully disconnect the application or notify other services or applications before you stop the application. EDAS integrates the lifecycle hook feature based on Kubernetes. This allows you to configure PostStart and PreStop hooks for containers.

To deploy an application to a Kubernetes cluster, check whether the pods are alive and ready to provide services. EDAS integrates the pod probe configuration feature based on Kubernetes. This feature allows you to configure the Liveness probe to determine the time to restart containers and configure the Readiness probe to determine whether containers are ready to receive traffic.

Configure application lifecycle hooks and probes when you create an application

  1. Log on to the EDAS console.
  2. In the left-side navigation pane, click Applications. In the top navigation bar, select a region. On the Applications page, select a namespace in the upper part and click Create Application in the upper-left corner.
  3. In the Basic Information step, specify Cluster Type and Application Runtime Environment, and click Next.
    Parameter Description
    Cluster Type Select Kubernetes Clusters.
    Application Runtime Environment Select an application runtime environment based on the type of the hosted application.
    • Java
      • Custom: Select this option if you want to use a custom image to deploy the application in a Kubernetes cluster.
      • Java: Select this option if you want to use a universal JAR package to deploy the application as a Dubbo or a Spring Boot application. You can specify the Java Environment parameter after you select this option.
      • Tomcat: Select this option if you want to use a universal WAR package to deploy the application as a Dubbo or a Spring application. You can specify the Java Environment and Container Version parameters after you select this option.
      • EDAS-Container (HSF): Select this option if you want to use a WAR or FatJar package to deploy the application as a High-Speed Service Framework (HSF) application. You can specify the Java Environment, Pandora Version, and Ali-Tomcat Version parameters after you select this option.
    • PHP: Select this option if you want to run this application as a PHP application on Apache HTTP Server.
    • Node.js, C ++, Go, and Other Languages: Select this option if you want to use a custom image to deploy the application in a Kubernetes cluster. The configuration process for multi-language applications is not described in this topic. For more information, see Use custom images to deploy applications of different programming languages in Kubernetes clusters.
  4. In the Configurations step, configure the environment information, basic information, deployment method, and resource parameters for the application, and click Next.
  5. In the Advanced Settings step, click Application Life Cycle Management and set parameters in the following table.
    Parameter Description
    PostStart A container hook. The hook is immediately triggered after a container is created. The hook notifies the container that the hook is created. The hook does not pass parameters to the corresponding hook handler. If the corresponding hook handler fails to run, the container is stopped and the restart policy of the container is used to determine whether to restart the container. For more information, see Container lifecycle hooks.
    PreStop A container hook. The hook is triggered before a container is deleted. The corresponding hook handler must be run before the request to delete the container is sent to the Docker daemon. The Docker daemon sends a SIGTERM semaphore to itself to delete the container, regardless of the running result of the corresponding hook handler. For more information, see Container lifecycle hooks.
    Liveness A probe that monitors your container status. The probe checks whether your applications are healthy. If an application is unhealthy, its corresponding container is deleted and recreated. For more information, see Pod lifecycle.
    Readiness A probe that monitors your container status. The probe checks whether your applications have been started and are running as expected. If an application is not running as expected, the container status is updated. For more information, see Pod lifecycle.
  6. Click Create Application.
  7. In the Creation Completed step, confirm the settings in Basic Information, Configurations, and Advanced Settings, and click Create Application.
    In the upper part of the Application Overview page, click View Details. On the Change List page, you can view the change process. Wait a few minutes until the application is deployed. After the change process is complete, view the running status of the instances in the Basic Information section of the Application Overview page. If the pod that runs the application is in the running state, the application is deployed.

Configure application lifecycle hooks and probes when you update an application

You can configure application lifecycle hooks and probes when you create an application, or configure or update hooks and probes when you deploy an application.

  1. Log on to the EDAS console.
  2. In the left-side navigation pane, click Applications. In the top navigation bar, select a region. On the Applications page, select a namespace in the upper part, and select Container Service or Serverless Kubernetes Cluster from the Cluster Type drop-down list. Then, find the application that you want to deploy, and click the application name.
  3. On the Application Overview or Basic Information page, choose Deploy > Deploy in the upper-right corner.
  4. On the Select Deployment Mode page, select a deployment mode and click Start Deployment in the upper-right corner of the specified deployment mode section.
  5. Set the environment and deployment package for an application, click Application Life Cycle Management, complete the configuration as needed, and then click OK.
    Parameter Description
    PostStart A container hook. The hook is immediately triggered after a container is created. The hook notifies the container that the hook is created. The hook does not pass parameters to the corresponding hook handler. If the corresponding hook handler fails to run, the container is stopped and the restart policy of the container is used to determine whether to restart the container. For more information, see Container lifecycle hooks.
    PreStop A container hook. The hook is triggered before a container is deleted. The corresponding hook handler must be run before the request to delete the container is sent to the Docker daemon. The Docker daemon sends a SIGTERM semaphore to itself to delete the container, regardless of the running result of the corresponding hook handler. For more information, see Container lifecycle hooks.
    Liveness A probe that monitors your container status. The probe checks whether your applications are healthy. If an application is unhealthy, its corresponding container is deleted and recreated. For more information, see Pod lifecycle.
    Readiness A probe that monitors your container status. The probe checks whether your applications have been started and are running as expected. If an application is not running as expected, the container status is updated. For more information, see Pod lifecycle.
    Notice The application is restarted after you click OK. We recommend that you perform this operation during off-peak hours.

Verify the result

After you configure an application lifecycle hook, you can perform the following steps to verify the configuration:

For example, configure the write script Hello from the postStart handler before you start an application.

After you deploy the application, use webshell to check whether the Hello from the postStart handler script exists. If yes, the configuration is successful. Lifecycle configured