sloth

packaged by Chainguard

Chainguard Container for sloth

Sloth generates Prometheus SLO recording and alerting rules from a simple spec, as a CLI, an HTTP server, or a Kubernetes controller that reconciles PrometheusServiceLevel resources into prometheus-operator PrometheusRule objects.

Chainguard Containers are regularly-updated, secure-by-default container images.

Download this Container Image

For those with access, this container image is available on cgr.dev:

docker pull cgr.dev/ORGANIZATION/sloth:latest

Be sure to replace the ORGANIZATION placeholder with the name used for your organization's private repository within the Chainguard Registry.

Compatibility Notes

Chainguard's sloth image is comparable to the upstream sloth image in functionality. The binary is available at /usr/local/bin/sloth, the path the upstream image and Helm chart use, and the image runs as the nonroot user 65532 with /home/nonroot as its working directory, matching upstream.

One binary provides three modes, all available here:

The dashboard that server mode serves at /u loads its JavaScript and CSS (htmx, uPlot, Alpine.js, and Pico CSS) from unpkg.com and cdn.jsdelivr.net, as it does upstream. The browser viewing the dashboard needs to reach those hosts, otherwise the pages load without search, charts, or range selection.

Getting Started

Generate Prometheus rules from an SLO spec without any cluster. Create a spec:

cat > sloth.yml <<EOF
version: "prometheus/v1"
service: "myservice"
labels:
  owner: "myteam"
slos:
  - name: "requests-availability"
    objective: 99.9
    description: "Common SLO based on availability for HTTP request responses."
    sli:
      events:
        error_query: sum(rate(http_request_duration_seconds_count{job="myservice",code=~"(5..|429)"}[{{.window}}]))
        total_query: sum(rate(http_request_duration_seconds_count{job="myservice"}[{{.window}}]))
    alerting:
      name: MyServiceHighErrorRate
      page_alert:
        labels:
          severity: pageteam
      ticket_alert:
        labels:
          severity: slack
EOF

Then run generate against it. The container runs as the calling user so it can read the mounted file:

docker run --rm -u "$(id -u):$(id -g)" -v "$PWD:/work" \
  cgr.dev/ORGANIZATION/sloth:latest generate -i /work/sloth.yml

The output is a Prometheus rules document containing the multi-window, multi-burn-rate recording rules and the alerting rules derived from the objective:

    - record: slo:sli_error:ratio_rate5m
    - alert: MyServiceHighErrorRate

validate checks a spec without generating anything, which is useful in CI:

docker run --rm -u "$(id -u):$(id -g)" -v "$PWD:/work" \
  cgr.dev/ORGANIZATION/sloth:latest validate -i /work/sloth.yml

Running as a Kubernetes Controller

In controller mode sloth watches PrometheusServiceLevel resources and writes prometheus-operator PrometheusRule objects. Upstream publishes the chart to a Helm repository, so add it first:

helm repo add sloth https://slok.github.io/sloth
helm repo update

The PrometheusRule CRD must exist before installing. If you are not already running prometheus-operator, upstream carries a copy of it:

kubectl apply --server-side -f https://raw.githubusercontent.com/slok/sloth/main/test/integration/crd/prometheus-operator-crd.yaml

Point the chart at this image with a values file. The chart composes the image reference from a separate registry and repository, so the host goes in global.imageRegistry:

cat > values.yaml <<EOF
global:
  imageRegistry: cgr.dev
image:
  repository: ORGANIZATION/sloth
  tag: latest
# Renders a PodMonitor, whose CRD the file above does not carry.
metrics:
  enabled: false
EOF

Then install the chart:

helm install sloth sloth/sloth \
  --namespace sloth --create-namespace \
  --values values.yaml --wait

The upstream example targets the monitoring namespace, so create it first. Applying the PrometheusServiceLevel then produces a PrometheusRule in that namespace:

kubectl create namespace monitoring
kubectl apply -f https://raw.githubusercontent.com/slok/sloth/main/examples/k8s-getting-started.yml
kubectl get prometheusrule -n monitoring

Configuration

The chart enables a git-sync sidecar by default, which clones the common SLI plugins into the path sloth loads plugins from. The chart mounts that volume at /git, the root of the upstream registry.k8s.io/git-sync/git-sync image it defaults to. Chainguard's git-sync image clones into /tmp/git instead, so pointing commonPlugins.image at it leaves the volume empty and sloth loads no SLI plugins. In an air-gapped cluster, or where you supply your own plugins, turn the sidecar off:

cat > values.yaml <<EOF
global:
  imageRegistry: cgr.dev
image:
  repository: ORGANIZATION/sloth
  tag: latest
commonPlugins:
  enabled: false
metrics:
  enabled: false
sloth:
  logger: json
EOF

metrics.enabled renders a PodMonitor, another prometheus-operator kind that the file above does not include, so enable it only on a cluster already running prometheus-operator. sloth serves its metrics on port 8081 either way. To see every value the chart accepts:

helm show values sloth/sloth

Documentation and Resources

• Sloth documentation
• Sloth GitHub project
• SLO spec reference
• Kubernetes CRD spec reference
• CLI usage
• Getting started guide

What are Chainguard Containers?

Chainguard's free tier of Starter container images are built with Wolfi, our minimal Linux undistro.

All other Chainguard Containers are built with Chainguard OS, Chainguard's minimal Linux operating system designed to produce container images that meet the requirements of a more secure software supply chain.

The main features of Chainguard Containers include:

• Minimal design, without unnecessary software bloat
• Daily builds to ensure container images are up-to-date with available security patches
• High quality build-time SBOMs attesting to the provenance of all artifacts within the image
• Verifiable signatures provided by Sigstore
• Reproducible builds with Cosign and apko (read more about reproducibility)

For cases where you need container images with shells and package managers to build or debug, most Chainguard Containers come paired with a development, or -dev, variant.

In all other cases, including Chainguard Containers tagged as :latest or with a specific version number, the container images include only an open-source application and its runtime dependencies. These minimal container images typically do not contain a shell or package manager.

Although the -dev container image variants have similar security features as their more minimal versions, they include additional software that is typically not necessary in production environments. We recommend using multi-stage builds to copy artifacts from the -dev variant into a more minimal production image.

Need additional packages?

To improve security, Chainguard Containers include only essential dependencies. Need more packages? Chainguard customers can use Custom Assembly to add packages, either through the Console, chainctl, or API.

To use Custom Assembly in the Chainguard Console: navigate to the image you'd like to customize in your Organization's list of images, and click on the Customize image button at the top of the page.

Learn More

Refer to our Chainguard Containers documentation on Chainguard Academy. Chainguard also offers VMs and Libraries — contact us for access.

Trademarks

This software listing is packaged by Chainguard. The trademarks set forth in this offering are owned by their respective companies, and use of them does not imply any affiliation, sponsorship, or endorsement by such companies.