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README.md

Examples

Runnable examples demonstrating Reaper's capabilities. Each example includes a setup.sh script that creates a Kind cluster with Reaper pre-installed.

Prerequisites

All examples require:

  • Docker
  • kind
  • kubectl
  • Helm (for examples using setup-playground.sh)

Note: Examples 01–08 use the legacy Ansible-based installer. Newer examples (09+) use the Helm-based setup-playground.sh pattern.

Run all scripts from the repository root.

Examples

01-scheduling/ — Node Scheduling Patterns

Demonstrates running workloads on all nodes vs. a labeled subset using DaemonSets with nodeSelector.

  • 3-node cluster (1 control-plane + 2 workers)
  • All-node DaemonSet (load/memory monitor on every node)
  • Subset DaemonSet (login-node monitor only on node-role=login nodes)
./examples/01-scheduling/setup.sh
kubectl apply -f examples/01-scheduling/all-nodes-daemonset.yaml
kubectl apply -f examples/01-scheduling/subset-nodes-daemonset.yaml

02-client-server/ — TCP Client-Server Communication

Demonstrates cross-node networking with a socat TCP server on one node and clients connecting from other nodes over host networking.

  • 4-node cluster (1 control-plane + 3 workers)
  • Server on role=server node, clients on role=client nodes
  • Clients discover the server IP via a ConfigMap
./examples/02-client-server/setup.sh
kubectl apply -f examples/02-client-server/server-daemonset.yaml
kubectl apply -f examples/02-client-server/client-daemonset.yaml
kubectl logs -l app=demo-client --all-containers --prefix -f

03-client-server-runas/ — Client-Server with Non-Root User

Same as client-server, but all workloads run as a shared non-root user (demo-svc, UID 1500 / GID 1500), demonstrating Reaper's securityContext.runAsUser / runAsGroup support. The setup script creates the user on every node with identical IDs, mimicking an LDAP environment.

  • 4-node cluster (1 control-plane + 3 workers)
  • Shared demo-svc user created on all nodes (UID 1500, GID 1500)
  • All log output includes uid= to prove privilege drop
./examples/03-client-server-runas/setup.sh
kubectl apply -f examples/03-client-server-runas/server-daemonset.yaml
kubectl apply -f examples/03-client-server-runas/client-daemonset.yaml
kubectl logs -l app=demo-client-runas --all-containers --prefix -f

04-volumes/ — Kubernetes Volume Mounts

Demonstrates Reaper's volume mount support across four volume types: ConfigMap, Secret, hostPath, and emptyDir. Showcases package installation (nginx) inside the overlay namespace without modifying the host.

  • 2-node cluster (1 control-plane + 1 worker)
  • ConfigMap-configured nginx, read-only Secrets, hostPath file serving, emptyDir scratch workspace
  • Software installed inside pod commands via overlay (host unmodified)
./examples/04-volumes/setup.sh
kubectl apply -f examples/04-volumes/configmap-nginx.yaml
kubectl logs configmap-nginx -f

05-kubemix/ — Kubernetes Workload Mix

Demonstrates running Jobs, DaemonSets, and Deployments simultaneously on a 10-node cluster. Each workload type targets a different set of labeled nodes, showcasing Reaper across diverse Kubernetes workload modes. All workloads read configuration from dedicated ConfigMap volumes.

  • 10-node cluster (1 control-plane + 9 workers)
  • Workers partitioned: 3 batch (Jobs), 3 daemon (DaemonSets), 3 service (Deployments)
  • Each workload reads config from its own ConfigMap volume
./examples/05-kubemix/setup.sh
kubectl apply -f examples/05-kubemix/
kubectl get pods -o wide

06-ansible-jobs/ — Ansible Jobs

Demonstrates overlay persistence by running sequential Jobs: the first installs Ansible via apt, the second runs an Ansible playbook (from a ConfigMap) to install and verify nginx. Packages installed by Job 1 persist in the shared overlay for Job 2.

  • 10-node cluster (1 control-plane + 9 workers)
  • Job 1: installs Ansible on all workers (persists in overlay)
  • Job 2: runs Ansible playbook from ConfigMap to install nginx
./examples/06-ansible-jobs/setup.sh
kubectl apply -f examples/06-ansible-jobs/install-ansible-job.yaml
kubectl wait --for=condition=Complete job/install-ansible --timeout=300s
kubectl apply -f examples/06-ansible-jobs/nginx-playbook-job.yaml

07-ansible-complex/ — Ansible Complex (Reboot-Resilient)

Fully reboot-resilient Ansible deployment using only DaemonSets. A bootstrap DaemonSet installs Ansible, then role-specific DaemonSets run playbooks (nginx on login nodes, htop on compute nodes). Init containers create implicit dependencies so a single kubectl apply -f deploys everything in the right order. All packages survive node reboots.

  • 10-node cluster (1 control-plane + 9 workers: 2 login, 7 compute)
  • 3 DaemonSets: Ansible bootstrap (all), nginx (login), htop (compute)
  • Init container dependencies — no manual ordering needed
./examples/07-ansible-complex/setup.sh
kubectl apply -f examples/07-ansible-complex/
kubectl rollout status daemonset/nginx-login --timeout=300s

08-mix-container-runtime-engines/ — Mixed Runtime Engines

Demonstrates mixed runtime engines in the same cluster: a standard containerized OpenLDAP server (default containerd/runc) alongside Reaper workloads that configure SSSD on every node. Reaper pods consume the LDAP service via a fixed ClusterIP, enabling getent passwd to resolve LDAP users on the host.

  • 4-node cluster (1 control-plane + 3 workers: 1 login, 2 compute)
  • OpenLDAP Deployment (default runtime) with 5 posixAccount users
  • Reaper DaemonSets: Ansible bootstrap + SSSD configuration (all workers)
  • Init containers handle dependency ordering (Ansible + LDAP readiness)
./examples/08-mix-container-runtime-engines/setup.sh
kubectl apply -f examples/08-mix-container-runtime-engines/
kubectl rollout status daemonset/base-config --timeout=300s

09-reaperpod/ — ReaperPod CRD

Demonstrates the ReaperPod Custom Resource Definition — a simplified, Reaper-native way to run workloads without container boilerplate. A reaper-controller watches ReaperPod resources and creates real Pods with runtimeClassName: reaper-v2 pre-configured.

  • No image: field needed (busybox placeholder handled automatically)
  • Reaper-specific fields: dnsMode, overlayName, simplified volumes
  • Status tracks phase, podName, nodeName, exitCode
# Prerequisites: install CRD and controller
kubectl create namespace reaper-system
kubectl apply -f deploy/kubernetes/crds/reaperpods.reaper.io.yaml
kubectl apply -f deploy/kubernetes/reaper-controller.yaml

# Run a simple task
kubectl apply -f examples/09-reaperpod/simple-task.yaml
kubectl get reaperpods
kubectl describe reaperpod hello-world

# With volumes (create ConfigMap first)
kubectl create configmap app-config --from-literal=greeting="Hello from ConfigMap"
kubectl apply -f examples/09-reaperpod/with-volumes.yaml

# With node selector (label a node first)
kubectl label node <name> workload-type=compute
kubectl apply -f examples/09-reaperpod/with-node-selector.yaml

10-slurm-hpc/ — Slurm HPC (Mixed Runtimes)

Demonstrates a Slurm HPC cluster using mixed Kubernetes runtimes: slurmctld (scheduler) runs as a standard container, while slurmd (worker daemons) run on compute nodes via Reaper with direct host access for CPU pinning and device management.

  • 4-node cluster (1 control-plane + 1 slurmctld + 2 compute)
  • slurmctld Deployment (default runtime) with munge authentication
  • slurmd DaemonSet (Reaper) on compute nodes with shared overlay
./examples/10-slurm-hpc/setup.sh
kubectl apply -f examples/10-slurm-hpc/
kubectl rollout status daemonset/slurmd --timeout=300s

11-node-monitoring/ — Node Monitoring (Prometheus + Reaper)

Demonstrates host-level node monitoring: Prometheus node_exporter runs as a Reaper DaemonSet for accurate host metrics, while a containerized Prometheus server (default runtime) scrapes them.

  • 3-node cluster (1 control-plane + 2 workers)
  • node_exporter DaemonSet (Reaper) — downloads and runs on host
  • Prometheus Deployment (default runtime) with Kubernetes service discovery
./examples/11-node-monitoring/setup.sh
kubectl apply -f examples/11-node-monitoring/
kubectl port-forward svc/prometheus 9090:9090

12-daemon-job/ — ReaperDaemonJob CRD (Node Configuration)

Demonstrates the ReaperDaemonJob Custom Resource Definition — a "DaemonSet for Jobs" that runs commands to completion on every matching node. Designed for node configuration tasks like Ansible playbooks that compose via shared overlays.

  • Dependency ordering via after field (second job waits for first)
  • Shared overlays via overlayName (composable node config)
  • Per-node status tracking with retry support
# Prerequisites: Reaper + controller running (via Helm or setup-playground.sh)
kubectl apply -f examples/12-daemon-job/simple-daemon-job.yaml
kubectl get reaperdaemonjobs
kubectl describe reaperdaemonjob node-info

# Composable example with dependencies
kubectl apply -f examples/12-daemon-job/composable-node-config.yaml
kubectl get rdjob -w   # watch until both jobs complete

Cleanup

Examples with setup.sh scripts can be cleaned up independently:

./examples/01-scheduling/setup.sh --cleanup
./examples/02-client-server/setup.sh --cleanup
./examples/03-client-server-runas/setup.sh --cleanup
./examples/04-volumes/setup.sh --cleanup
./examples/05-kubemix/setup.sh --cleanup
./examples/06-ansible-jobs/setup.sh --cleanup
./examples/07-ansible-complex/setup.sh --cleanup
./examples/08-mix-container-runtime-engines/setup.sh --cleanup
./examples/10-slurm-hpc/setup.sh --cleanup
./examples/11-node-monitoring/setup.sh --cleanup

For CRD-based examples (09, 12), delete the resources directly:

kubectl delete reaperpod --all
kubectl delete reaperdaemonjob --all