allow usage of seconds in cron

[elee1766]

it would be nice to have support for to run a job every n seconds, so i can do health monitoring every 5 seconds instead of every minute.

the cron libraries you use has support for seconds parsing, both in the frontend https://www.npmjs.com/package/cron-parser and in the backend https://github.com/robfig/cron?tab=readme-ov-file#upgrading-to-v3-june-2019

e.g.

cron.New(cron.WithParser(cron.NewParser(
	cron.SecondOptional | cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow | cron.Descriptor,
)))

so maybe it just has to be enabled ?

currently im using cronicle to check every 5 seconds, but i want to switch to dagu.

[yohamta]

Hey, thank you for the excellent suggestion! It sounds like a promising idea, and I was thinking about whether it's feasible. Here are the changes that would need to be made:

• Update the schedule parser: https://github.com/dagu-org/dagu/blob/main/internal/dag/parser.go#L37
• Update the Scheduler: https://github.com/dagu-org/dagu/blob/main/internal/scheduler/scheduler.go#L170
• Frontend: Next run calculation - https://github.com/dagu-org/dagu/blob/main/ui/src/models/index.ts#L148
  Some considerations:

The scheduler currently ticks every minute. If it runs every second, that might be too frequent, so we'll need to think about how to manage that. Running per second could generate a lot of log and status files on disk, which might lead to inode capacity or performance issues. I believe it's possible, but at the moment, running every second might add too much overhead, and I’m not sure it’s worth it.

My suggestion is to create a loop inside the DAG to achieve a similar effect. For example:

schedule: "* * * * *"
steps:
  - name: health check
     command: bash
     run: |
        #!/bin/bash
        health_check() {
            echo "Performing health check..."
        }
  
        duration=60
        start_time=$(date +%s)
  
        while true; do
            current_time=$(date +%s)
            elapsed=$((current_time - start_time))
  
            if [ $elapsed -ge $duration ]; then
                echo "Health check completed after 1 minute."
                break
            fi
  
            health_check
  
            sleep 1
        done