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Updated on 2022-02-22 GMT+08:00
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Template Compilation Skills

Waiting for Component Start-up

Assume that the "A" (application) and "S" (service) components need to be started, "A" depends on "S", and "A" needs to connect to "S" to provide services. In the following example, "A" is Tomcat and "S" is MySQL.

During Application Orchestration Service (AOS) orchestration, "S" is first started based on the template. After "S" is started successfully (its process is started successfully, but its service function is still unavailable), "A" is then started. If "A" is connected to "S" before the "S" service function is completely started, "A" fails to be started. As a result, the entire stack fails to be started. Therefore, you may need to wait for a period of time before starting "A".

Currently, the waiting logic is not supported in the template syntax. To solve the problem, add the waiting logic to the service process.

The following is an example of waiting for a period of time before starting a component:

name:  # Parameter name
  type: string  # Parameter type
  description: resource name  # Parameter description
Task-Name: # Task name (user defined)
  description: sleep before business
  actions:
    poststart: # Execute scripts before startup.
      command: "/bin/sh, -c, sleep

Converting Numbers into Strings

In many cases, variables are defined as strings, but they sometimes need to be referenced as numbers. For example, when the port number is used as an environment variable, the value must be a string. When the port number is used as a microservice attribute, the value must be a number.

To solve the preceding problem, use either of the following methods:

  • Method 1: Define two variables.

    Define the PORT-i and PORT-s variables. PORT-s is a string, while PORT-i is a number. This method can directly be used to solve the preceding problem, but the effect is not ideal. Due to duplication, the maintainability and usability of the template deteriorate.

  • Method 2: Use the concat built-in function.

    Use the concat built-in function to combine multiple small strings into a longer and more complete string. The parameters of the concat built-in function can be any type of variable, supporting the combination of numbers and strings. Example command:

    First, define variables as follows:

    magento-EPORT:
  type: integer
  default: 32080

    When the parameter indicates a ULR, ensure that its value is a string:

    name: MAGENTO_URL
  value: 
    concat:
    - "http://"
    - {get_input: magento-EIP}
    - ":"
    - {get_input: magento-EPORT}  #Convert a number to a string.

    When the parameter indicates a microservice attribute, ensure that its value is a number:

    serviceSpec:
  ports:
    - port: {get_input: magento-container-port}
      nodePort: {get_input: magento-EPORT}  #The value must be a number.
Parent topic: Template Introduction