sloth
Sloth is a Go-based tool that automatically generates Prometheus SLO (Service Level Objective) metrics and alerting rules from simple YAML specifications. It implements Google's SRE best practices including multi-window multi-burn-rate alerts, reducing manual configuration and standardizing SLO definitions across teams.
Key facts
Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.
| Field | Value |
|---|---|
| Repository | slok/sloth |
| Owner | slok |
| Primary language | Go |
| License | Apache-2.0 — OSI-approved |
| Stars | 2.5k |
| Forks | 223 |
| Open issues | 16 |
| Latest release | v0.16.0 (2026-04-04) |
| Last updated | 2026-06-19 |
| Source | https://github.com/slok/sloth |
What sloth is
Sloth parses SLO manifests to generate Prometheus recording rules, SLI metrics across multiple time windows, and alert rules (page and ticket severity). It supports Kubernetes operators via Prometheus-operator CRDs, OpenSLO format, and pluggable SLI implementations. The tool validates specs and outputs Prometheus-compatible rule files.
Get the sloth source
Clone the repository and explore it locally.
git clone https://github.com/slok/sloth.gitcd sloth# follow the project's README for install & configurationNeed it deployed, integrated, or customized instead? DEV.co ships production installs.
Best use cases
Implementation considerations
- Define SLO objectives and error budgets upfront; Sloth enforces Google SRE methodology but requires domain alignment on what 'reliable' means per service.
- Plan SLI query design carefully—Sloth auto-generates recording rules, so accurate error_query and total_query definitions are critical to avoid cascading alert noise.
- Integrate Sloth into CI/CD to validate specs before deployment; the `validate` command prevents invalid configurations from reaching Prometheus.
- Configure alerting destinations (PagerDuty, Slack, etc.) outside Sloth via alert rules metadata labels; Sloth does not handle notification routing.
- Test burn-rate thresholds in staging; multi-window multi-burn-rate alerts are sensitive to metric cardinality and can generate false positives if SLIs are noisy.
When to avoid it — and what to weigh
- Prometheus Not Your Metrics Backend — Sloth is tightly coupled to Prometheus. If your observability stack uses Datadog, New Relic, or other vendors, Sloth does not directly support those backends.
- Existing Complex Custom Alert Logic — If your organization has highly customized alerting thresholds or non-standard burn-rate calculations, Sloth's opinionated SRE model may require significant workarounds.
- Teams Without Prometheus Expertise — Effective SLO definition requires understanding PromQL, metric cardinality, and recording rules. Teams unfamiliar with Prometheus will face a steep learning curve.
- Real-Time SLO Recalculation Needs — Sloth generates static rule files; it does not dynamically recalculate SLOs based on live traffic anomalies or environment changes without regeneration.
License & commercial use
Sloth is licensed under Apache License 2.0, a permissive OSI-approved license allowing commercial use, modification, and distribution with proper attribution and liability disclaimer.
Apache-2.0 permits commercial use without runtime fees or license restrictions. No proprietary vendor lock-in. Verify your legal team accepts ASF-style copyleft clauses (notice preservation, liability waiver) for your use case.
DEV.co evaluation signals
Editorial assessment — not user reviews. Directional, with an explicit confidence level.
| Signal | Assessment |
|---|---|
| Maintenance | Active |
| Documentation | Strong |
| License clarity | Clear |
| Deployment complexity | Moderate |
| DEV.co fit | Strong |
| Assessment confidence | High |
Sloth does not directly handle authentication or encryption. Security posture depends on Prometheus cluster hardening, RBAC (if Kubernetes-deployed), and protection of generated alert rule files. No known public CVEs identified in provided data. Evaluate generated Prometheus rules for unintended metric exposure.
Alternatives to consider
Prometheus-Community alert-rules
Community-maintained static alert rule templates. Lower automation; requires manual SLO spec-to-rules translation, but no tool dependency.
Datadog SLO Management
Native SLO platform with UI-driven definition and vendor-managed alerting. Requires Datadog agent; tighter vendor lock-in but simpler operational model.
Grafana Mimir + Loki SLO plugins
Integrates with Grafana ecosystem for metrics and logs. Emerging SLO tooling but less mature than Sloth for Prometheus-native deployments.
Build on sloth with DEV.co software developers
Explore Sloth's documentation and getting-started examples to define SLOs uniformly for your Prometheus-monitored services. Start with a single service and expand across your platform.
Talk to DEV.coRelated open-source tools
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sloth FAQ
Does Sloth send alerts directly?
Can I use Sloth without Kubernetes?
What if my SLI metric is unavailable or noisy?
Is Sloth suitable for compliance (SOC2, FedRAMP)?
Work with a software development agency
From first prototype to production, DEV.co delivers software development services around tools like sloth. Our software development agency staffs experienced software developers and web developers for custom software development, web development, integrations, and ongoing support across open-source observability and beyond.
Ready to standardize SLOs across your services?
Explore Sloth's documentation and getting-started examples to define SLOs uniformly for your Prometheus-monitored services. Start with a single service and expand across your platform.