Keep instances warm on a schedule

Docker compatibleDocker Swarm compatiblePartially Kubernetes compatiblePodman compatibleProxmox LXC not yet implemented

Exampleexamples/running-hours

This guide shows you how to keep an instance available during specific daily hours with the sablier.running-hours and sablier.running-days labels:

# compose.yml
services:
  myapp:
    image: myapp:latest
    restart: unless-stopped
    labels:
      - "sablier.enable=true"
      - "sablier.group=myapp"
      - "sablier.running-hours=09:00-18:00"
      - "sablier.running-days=Mon,Tue,Wed,Thu,Fri"

The instance is proactively started and held warm for the whole window regardless of traffic. Two labels drive it:

• sablier.running-hours: the daily window, 24-hour HH:MM-HH:MM (e.g. 09:00-18:00). Overnight windows like 22:00-06:00 span midnight.
• sablier.running-days: optional, restricts the window to specific weekdays (comma-separated, full names or abbreviations, e.g. Mon,Tue,Wed,Thu,Fri). Defaults to every day.

    flowchart LR
    before["Before 09:00<br/>request-triggered only"]
    open["09:00 window start<br/>Sablier starts instance"]
    during["Inside window<br/>held warm, sessions extended to window end"]
    after["18:00 window end<br/>normal expiration resumes"]
    before --> open --> during --> after
  

Behavior:

• At the beginning of the window, Sablier proactively starts the instance.
• During the window, request-triggered sessions are extended to the window end so the instance is not stopped mid-window.
• After the window ends, normal session expiration resumes.
• For overnight windows, the day is evaluated against the day the window starts (a Fri + 22:00-06:00 window runs from Friday 22:00 to Saturday 06:00).

Timezone (TZ)

Running-hours are evaluated in the process local timezone.

• In the official Docker image, the binary embeds timezone database data and supports TZ out of the box.
• The container defaults to TZ=UTC.
• Override with an environment variable, e.g. -e TZ=Europe/Paris.

Format rules

• sablier.running-hours: 24-hour HH:MM-HH:MM. If start is later than end, the window spans midnight. Unparseable values are ignored.
• sablier.running-days: comma-separated days; full names (Monday) and abbreviations (Mon); case-insensitive; whitespace ignored. Unparseable values are ignored (the window then applies every day).