Resource Efficiency

Sablier saves resources by stopping containers when nobody is using them and starting them back on demand. This page explains how to measure those savings.

How Sablier saves resources

Without Sablier, every container runs 24 hours a day whether it is being used or not. With Sablier, a container runs only when a request triggers it, then stops automatically after a configurable idle timeout.

The saving is in the idle dimension: the hours per day a container is not being used. A typical homelab service might be accessed for 1-3 hours a day, meaning it is idle 88-96 % of the time. Stopping it during those idle hours reclaims CPU, RAM, and the power that drives both.

Enabling metrics

Add the following to your Sablier configuration:

server:
  metrics:
    enabled: true

Metrics are then available at http://<sablier-host>:10000/metrics.

The key metric: sablier_instance_active_seconds_total

Sablier exports a counter that accumulates the total seconds each instance has spent in the Ready state:

sablier_instance_active_seconds_total{instance="<name>"}

The counter is incremented each time a session expires (i.e., the container is stopped because it became idle). It does not count startup time.

Use it to compute the idle fraction over any window. This is your efficiency gain:

1 - (increase(sablier_instance_active_seconds_total{instance="myapp"}[24h]) / 86400)

Returns a value between 0 and 1. Example: 0.92 means the container was stopped and consuming no resources 92 % of the day.

Computing resource savings

Once you have the idle fraction, multiply by the container’s idle cost:

$$\text{savings} = \text{idle fraction} \times \text{idle resource cost} \times N_{\text{containers}}$$

Example: homelab with 5 containers

CPU reclaimed per day:

$$0.92 \times 0.04 \times 5 \times 24\text{ h} = 4.4 \text{ CPU-hours/day}$$

RAM reclaimed when all containers are idle:

$$0.92 \times 150\text{ MB} \times 5 = 690\text{ MB}$$

To measure a container’s idle cost, stop all traffic and run:

docker stats --no-stream --format \
  "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}"

What Sablier itself costs

Sablier’s own process is lightweight, typically under 0.5 % CPU and 20 MB RAM, and does not stop running between requests. In practice its overhead is negligible compared to the resources saved by even a single stopped container.

See also

• Metrics reference
• Performance benchmarks
• Tracing