change_script.mdx

layout	page_title	description
docs	change_script Block - Job Specification	The "change_script" block configures a script to be run on template re-render.

change_script Block

<Placement groups={['job', 'group', 'task', 'template', 'change_script']} />

The change_script block allows operators to configure scripts that will be executed on template change. This block is only used when template change_mode is set to script.

job "docs" {
  group "example" {
    task "server" {
      template {
        source      = "local/redis.conf.tpl"
        destination = "local/redis.conf"
        change_mode = "script"
        change_script {
          command       = "/bin/foo"
          args          = ["-verbose", "-debug"]
          timeout       = "5s"
          fail_on_error = false
        }
      }
    }
  }
}

change_script Parameters

• command (string: "") - Specifies the full path to a script or executable that is to be executed on template change. The command must return exit code 0 to be considered successful. Path is relative to the driver, e.g., if running with a container driver the path must be existing in the container. This option is required if change_mode is script.

• args (array<string>: []) - List of arguments that are passed to the script that is to be executed on template change.

• timeout (string: "5s") - Timeout for script execution specified using a label suffix like "30s" or "1h".

• fail_on_error (bool: false) - If true, Nomad will kill the task if the script execution fails. If false, script failure will be logged but the task will continue uninterrupted.

Template as a script example

Below is an example of how a script can be embedded in a data block of another template block:

job "docs" {
  group "example" {
    task "server" {
      template {
        data        = "{{key \"my_key\"}}"
        destination = "local/test"
        change_mode = "script"

        change_script {
          command = "/local/script.sh"
        }
      }

      template {
        data        = <<EOF
#!/usr/bin/env bash
echo "Running change_mode script"
sleep 10
echo "Done"
EOF
        destination = "local/script.sh"
        perms       = "777"
      }
    }
  }
}