Configuring the Startup Command and Lifecycle of a Component

Lifecycle Callback Functions

ServiceStage provides the following lifecycle callback functions:

• Startup command: corresponds to the ENTRYPOINT startup command of Docker, and is used to start an application component.
• Post-start processing: triggered after an application component is started.
• Pre-stop processing: triggered before an application component is stopped.

Configuring the Startup Command and Lifecycle of a Component

1. Choose Container Settings.
2. Click Startup Command to set Command and Parameter for the container.

   A Docker image has metadata that stores image information. If no Lifecycle command or parameter is set, the container runs the default command and parameter provided during image creation. The Docker defines the default command and parameter as CMD and Entrypoint. For details about the two fields, see Entrypoint Description and CMD Description.

   If the running command and parameter of the application are set during application component deployment, the default Entrypoint and CMD will be overwritten during image building. Table 1 describes the rules.

   Table 1 Startup command parameters

   Image Entrypoint	Image CMD	Application Running Command	Application Running Parameter	Final Execution
   [touch]	[/root/test]	Not set	Not set	[touch /root/test]
   [touch]	[/root/test]	[mkdir]	Not set	[mkdir]
   [touch]	[/root/test]	Not set	[/opt/test]	[touch /opt/test]
   [touch]	[/root/test]	[mkdir]	[/opt/test]	[mkdir /opt/test]

   1. Command: Enter an executable command, for example, /run/server.
      

      If there are multiple commands, you are advised to run /bin/sh or other shell commands. Other commands are used as parameters.

   2. Parameter: Enter a parameter that controls the container running command, for example, --port=8080. If there are multiple parameters, separate them in different lines.

3. Click Lifecycle and set Post-Start and Pre-Stop parameters. Table 2 describes the parameters. Select one of the parameters.

   Table 2 Container lifecycle parameters

   Parameter	Description
   CLI mode	Command to be executed in the component instance. The command format is Command Args[1] Args[2]…. Command is a system command or a user-defined executable program. If no path is specified, an executable program in the default path will be selected. If multiple commands need to be executed, write the commands into a script for execution. For example, the following commands need to be executed: exec: command: - /install.sh - install_agent Write /install.sh install_agent in the script. This command indicates that the agent will be installed after the component is deployed.
   HTTP request mode	HTTP call request. The related parameters are described as follows: Path: (optional) URL of a request. Port: (mandatory) request port. Host Address: (optional) IP address of the request. The default value is the IP address of the node where the application is located.