action Block

Placement	`job -> group -> task -> action`

The action block allows job authors to define custom commands. These commands can be executed by operators with the necessary permissions on a running allocation, offering a controlled way to interact with tasks.

`action` Parameters

command (string: <required>) - Specifies the command to be executed.
args (array<string>: []) - Provides a list of arguments to pass to the command.

job "my-job" {
  group "my-group" {
    task "my-task" {
      action "get-changelog" {
        command = "/usr/bin/curl"
        args = [
          "-s",
          "https://raw.githubusercontent.com/hashicorp/nomad/main/CHANGELOG.md"
        ]
      }
      # ...
    }
  }
}

`action` Examples

Basic Action

This example demonstrates a simple action that prints the current date and time:

job "example" {
  # ...
  group "demo" {
    # ...
    task "show-date" {
      # ...
      action "current-date" {
        command = "/bin/date"
      }
    }
  }
}

Action with Arguments

Here, an action uses arguments to perform a specific task:

job "example" {
  # ...
  group "demo" {
    # ...
    task "list-files" {
      # ...
      action "list-tmp" {
        command = "/bin/ls"
        args    = ["-l", "/tmp"]
      }
    }
  }
}

Action with Template

This advanced example demonstrates an action that fetches and formats the latest changelog from the Nomad GitHub repository using a shell script. It showcases the use of templating with embedded environment variables and a multi-line script.

action "fetch-latest-nomad-changelog" {
  command = "/bin/sh"
  args    = ["-c", 
    <<EOT
curl -s https://raw.githubusercontent.com/hashicorp/nomad/main/CHANGELOG.md | 

awk 'BEGIN{
    # Setting record and field separators
    RS="## "; FS="\n"; 
    section=""; count=0
}
{
    # Processing only the first 3 sections after the header
    if (count < 3 && NR > 1){
        # Splitting the version line into components
        split($1, versionInfo, /[()]/);
        version=versionInfo[1];
        gsub(" ", "", version); # Removing spaces from version
        releaseDate=versionInfo[2];
        # Formatting URL components
        urlVersion=version; gsub("\\.", "", urlVersion); # Remove dots from version
        urlDate=releaseDate; gsub(" ", "-", urlDate); gsub(",", "", urlDate); # Replace spaces with hyphens and remove comma
        # Counting items under each section
        for(i=1; i<=NF; i++){
            if($i ~ /^[A-Z ]+:$/){
                gsub(":", "", $i);
                section=$i;
                itemCount[section]=0;
            }
            if(section && $i ~ /^\*/){
                itemCount[section]++;
            }
        }
        # Printing the extracted information
        printf "Version: %s\nRelease Date: %s\n", version, releaseDate;
        for (s in itemCount) {
            printf "%d %s, ", itemCount[s], s;
        }
        printf "\nLink: https://github.com/hashicorp/nomad/blob/main/CHANGELOG.md#%s-%s\n\n", urlVersion, tolower(urlDate);
        delete itemCount;  # Clear the itemCount array for the next version
        count++;
    }
}'
    EOT
  ]
}