JS7 JobScheduler

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Table of Contents

Task

  • Users frequently find the situation that jobs in a workflow pass variables to subsequent jobs.

  • This can easily be achieved by appending a pair of name/value for the variable to a temporary file that is offered by the JS7_RETURN_VALUES environment variable like this:

    Code Block
    languagebash
    titleExample how to pass a variable to subsequent jobs with Unix
    MY_VAR="some text"
echo "my_variable=$MY_VAR" >> $JS7_RETURN_VALUES
    Code Block
    languagebash
    titleExample how to pass a variable to subsequent jobs with Windows
    set MY_VAR=some text
echo my_variable=%MY_VAR% >> %JS7_RETURN_VALUES%


    Explanation:

    • A variable my_variable is passed as an order variable to subsequent jobs and instructions in a workflow.
    • The variable can be assigned a constant value or a value from some environment variable as e.g. MY_VAR that holds some arbitrary value.
  • There However, there are two limitations about this approach:
    • The length of values for environment variables is limited, the precise max. size of environment variables is OS dependent.
    • If the value of the variable includes special characters such as carriage return, newline, linefeed then this might break depending on capabilities of environment variables in the echo command in the OS.

Solution

  • To address the problem of special characters use base64 encoding for variable values as this encoding results in a single printable string.
  • To address the limitation concerning the size of environment variables do not use them and think about ways how to directly append lines to the temporary file indicated by JS7_RETURN_VALUES. 

...

  • Let's assume two jobs to be executed in sequence:
    • the The first job creates a lengthy e-email body in HTML format,
    • the The second job sends e-mail and makes use of the HTML body.
    Job: create-mail-body
    • Find a number of possible implementations:


      Code Block
      languagebash
      titleExample for Shell version using environment variables on Unix
      #!/user/bin/env bash

mailBody="<html><body><b>hello</b> <i>world</i></body></html>"
mailBodyEncoded=$(echo $mailBody | base64
    • )
echo "body=base64:$mailBodyEncoded" >> $JS7_RETURN_VALUES
      Code Block
      languagebash
      titleExample for Shell version using files on Unix
      #!/user/bin/env bash

echo "<html><body><b>hello</b> <i>world</i></body></html>" > /tmp/mail-body.html
echo "body=base64:$(cat /tmp/mail-body.html | base64)" >> $JS7_RETURN_VALUES
      Code Block
      languagebash
      titleExample for PowerShell version on Unix
      #!/usr/bin/env pwsh

$mailBody = "<html><body><b>hello</b> <i>world</i></body></html>"
$mailBodyEncoded = [System.Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes( $mailBody ))
"body=base64:$mailBodyEncoded" | Out-File $env:JS7_RETURN_VALUES -Append



      Explanation:

      • In fact the e-mail body is not too lengthy, however, it suggests that an e-mail body would be

      created

      • imported by some template file as e.g. for PowerShell with $mailBody = Get-Content "mail-body.html"

      • Base64 encoding is available from a number of sources such as the base64 Unix utility or the .Net Core class.
      • The value of
      the e-mail
      • the body variable is prefixed with base64: to indicate the encoding.
      • The subsequent JS7 - JITL MailJob accepts the body variable and identifies the encoding and automatically decodes the argument value.
      • As a summary: you can base64 encode from a single command line