Pod Replica Count Check

Pod replica count check validates the current replica count of Kubernetes pods.

Infrastructure type

• Kubernetes

Use cases

Pod Replica Count Check probe helps you:

• Verify deployments maintain desired replica count
• Validate auto-scaling behavior during load chaos
• Monitor application availability during pod failures
• Ensure high availability during chaos experiments

---

Overview

This probe validates that Kubernetes resources (Deployments, StatefulSets, DaemonSets, etc.) maintain the minimum required number of healthy replicas during chaos experiments.

Probe type

Command Probe

Prerequisites

• Kubernetes cluster with chaos infrastructure installed
• Access to target namespace and resources
• Sufficient RBAC permissions to query resource status

---

Probe properties

Command

healthchecks -name validate-pod-replica

Comparator

Type	Criteria	Value
string	contains	[Pass]

The probe passes when the command output contains [Pass], indicating the resource has the minimum required healthy replicas.

Environment variables

Variable	Description	Required	Default
TARGET_LABELS	Comma-separated list of target labels to filter resources.	No	-
TARGET_NAMES	Comma-separated list of target resource names.	No	-
TARGET_NAMESPACE	Namespace of the target resources.	No	-
TARGET_KIND	Kind of the target resource (e.g., deployment, statefulset, daemonset).	No	deployment
MINIMUM_HEALTHY_REPLICA_COUNT	Minimum healthy replica count for the target.	No	1
STATUS_CHECK_TIMEOUT	Maximum time in seconds to wait for status check.	No	180
STATUS_CHECK_DELAY	Delay in seconds between status checks.	No	2

---

Run properties

Property	Description	Type	Default
timeout	Maximum time to wait for the probe to complete (e.g., 30s, 1m, 5m)	String	180s
interval	Time between probe executions (e.g., 1s, 5s, 10s)	String	1s
attempt	Number of retry attempts before marking the probe as failed	Integer	1
pollingInterval	Time between retry attempts (e.g., 1s, 5s, 10s)	String	-
initialDelay	Initial delay before starting the probe (e.g., 0s, 10s, 30s)	String	-
stopOnFailure	Stop the experiment if the probe fails	Boolean	false
verbosity	Log verbosity level (info, debug, trace)	String	-

---

Probe definition

You can define this probe in your chaos experiment as follows:

Using resource labels

probe:
  - name: "replica-count-validation"
    type: "cmdProbe"
    mode: "Continuous"
    cmdProbe/inputs:
      command: "healthchecks -name validate-pod-replica"
      comparator:
        type: "string"
        criteria: "contains"
        value: "[Pass]"
      env:
        - name: TARGET_LABELS
          value: "app=nginx,tier=frontend"
        - name: TARGET_NAMESPACE
          value: "production"
        - name: TARGET_KIND
          value: "deployment"
        - name: MINIMUM_HEALTHY_REPLICA_COUNT
          value: "3"
    runProperties:
      timeout: 180s
      interval: 1s
      attempt: 1
      stopOnFailure: false

Using resource names

probe:
  - name: "deployment-replica-check"
    type: "cmdProbe"
    mode: "Edge"
    cmdProbe/inputs:
      command: "healthchecks -name validate-pod-replica"
      comparator:
        type: "string"
        criteria: "contains"
        value: "[Pass]"
      env:
        - name: TARGET_NAMES
          value: "my-deployment,my-statefulset"
        - name: TARGET_NAMESPACE
          value: "default"
        - name: MINIMUM_HEALTHY_REPLICA_COUNT
          value: "2"
        - name: STATUS_CHECK_TIMEOUT
          value: "120"
    runProperties:
      timeout: 150s
      interval: 2s
      attempt: 3