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Labels & annotations

Labels & annotations

Sablier never modifies your application and keeps no central list of the workloads it manages. Instead, you opt each workload in and configure it declaratively, using the labelling mechanism your platform already provides. Sablier discovers what to manage by reading these labels from the provider.

Opt in with sablier.enable

A workload is managed by Sablier only when it carries the sablier.enable=true label. Without it, Sablier does not discover the workload and will not start or stop it.

services:
  whoami:
    image: acouvreur/whoami:v1.10.2
    labels:
      - "sablier.enable=true"
      - "sablier.group=demo"

Configure behaviour with sablier.* labels

Everything beyond opting in is optional and expressed the same way. Labels control which group(s) an instance belongs to, when it is kept warm, how readiness is decided, and how it scales:

  • sablier.group: the group(s) this instance belongs to (see Groups).
  • sablier.running-hours / sablier.running-days: keep the instance warm on a schedule.
  • sablier.ready-after / sablier.ready-on-start: tune when Sablier considers the instance ready.
  • sablier.idle.* / sablier.active.*: throttle CPU, memory and block I/O instead of stopping (see scale mode).

The Label reference documents every key, its type and the version it was introduced in.

Where labels live per provider

Each platform exposes labels differently, and Sablier reads them from the native location:

ProviderWhere Sablier reads configuration
Docker, Podmancontainer labels
Docker Swarmservice deploy.labels
Kubernetesworkload labels for sablier.enable, annotations for every other key
Proxmox LXCcontainer tags
On Kubernetes, sablier.enable must be a label because workload discovery uses a label selector; multi-value settings such as sablier.group must be annotations. On Proxmox LXC there are no key/value labels, so Sablier reads tags like sablier and sablier-group-<name>.

See Applying labels for copy-paste examples in each provider’s syntax.

Labels take effect as workloads change

Sablier reads labels when it discovers workloads and as they start, stop or are updated, so adding or editing a label does not require restarting Sablier. Removing sablier.enable (or all of an instance’s groups) simply drops the instance from Sablier’s management.

How Sablier worksGroups