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Pod network latency

Add a configurable delay to packets on a target Kubernetes pod's network path to test timeout, retry, and tail-latency behavior of upstream and downstream calls.

Pod network latency is a Kubernetes pod-level chaos fault that adds a configurable delay to packets on the network path serving a target pod for a configurable duration. Only the selected pods experience the delay; other pods on the node and the node's host networking are unaffected. When the fault ends, the delay is removed and the pod's network returns to normal immediately.

Use this fault to test how a service behaves when one or more replicas suddenly experience high latency to upstream dependencies, peers, or callers: a cross-region failover, a degraded WAN, a slow database, or a queue backed up under load.

RUN YOUR FIRST EXPERIMENT

If you have not configured the chaos infrastructure yet, go to Quickstart to install the chaos infrastructure and run an experiment end to end.

Use cases

Run this fault when you want to answer concrete questions like:

  • Timeout and retry budgets: When a downstream call takes 5 seconds instead of 50 ms, do clients honor sensible timeouts? Does the retry budget hold, or do callers amplify load?

  • Cross-region latency simulation: Before a multi-region migration, simulate inter-region latency and verify whether your read-after-write semantics still hold.

  • Connection pool sizing: Higher latency means more in-flight requests for the same throughput. Does the pool size up, or does the workload starve?

  • Service mesh failover: Does the mesh shift traffic away from the slow replica through outlier detection, or do the slow responses propagate?

  • Probe sensitivity: Are readiness and liveness probes resilient to short latency spikes, or do they oscillate the pod in and out of service?

Prerequisites

  • Kubernetes version: 1.21 or later. Go to What's supported to confirm distribution support.

  • Target pods are Running: The application pods you intend to target are in the Running state before the fault is launched.

  • Privileged pods allowed: The cluster lets you schedule privileged pods in the chaos namespace.

  • Workload selector defined: The chaos experiment knows the target workload by kind, namespace, and either names or labels.

Supported environments

Platform
Support status

Amazon EKS

Supported

Azure AKS

Supported

Google GKE

Supported

Red Hat OpenShift

Supported

Rancher

Supported

VMware Tanzu

Supported

Self-managed Kubernetes (CNCF-certified)

Supported

GKE Autopilot

Supported with Autopilot setup

EKS Fargate, ACI virtual nodes

Not supported (no access to container runtime sockets)

Permissions required

The fault runs under the chaos infrastructure's service account.

Resource (apiGroup)

Verbs

Why it is needed

pods ("")

get, list, create, delete, deletecollection, patch, update

Discover target pods and run the chaos pod on the same node

pods/log ("")

get, list, watch

Stream chaos pod logs for status and debugging

deployments, statefulsets, replicasets, daemonsets (apps)

get, list

Resolve the target workload to the pods it owns

events ("")

get, list, create, patch, update

Record fault progress as Kubernetes events

jobs (batch)

get, list, create, delete, deletecollection

Run the chaos job that drives the fault

The default Harness chaos infrastructure service account already includes these permissions.

Fault tunables

Configure the following fault parameters when you add Pod network latency to an experiment in Chaos Studio. Defaults are shown for reference.

Chaos parameters

Tunable
Description
Default

NETWORK_LATENCY

Latency to add to each packet. Accepts Go duration strings such as 100ms, 2s, 500us.

"2s"

JITTER

Random variation around NETWORK_LATENCY in milliseconds. 0 means perfectly fixed delay.

0

CORRELATION

Latency correlation as a percentage. 0 makes each packet's delay independent; higher values smooth the variation.

""

TOTAL_CHAOS_DURATION

Duration of the fault in seconds.

60

Traffic filters

Tunable
Description
Default

DESTINATION_IPS

Comma-separated list of destination IPs. Latency applies only to packets headed to these IPs. Empty matches all destinations.

""

DESTINATION_HOSTS

Comma-separated list of destination hostnames. The helper resolves them and adds the resolved IPs to the filter.

""

SOURCE_PORTS

Comma-separated list of source ports on the target pod. Empty matches all source ports.

""

DESTINATION_PORTS

Comma-separated list of destination ports. Empty matches all destination ports.

""

NETWORK_INTERFACE

Network interface inside the target container's namespace. Almost always eth0 for standard CNI plugins.

eth0

Targeting

Tunable
Description
Default

TARGET_PODS

Comma-separated list of pod names to target. Empty selects from the workload's pods using POD_AFFECTED_PERCENTAGE.

""

TARGET_CONTAINER

Container in the pod whose network namespace to enter. Empty targets the first container in the pod spec.

""

NODE_LABEL

Label selector to filter target pods by the node they run on. Empty disables node-based filtering.

""

POD_AFFECTED_PERCENTAGE

Percentage of the workload's pods to target. 0 means one pod.

0

SEQUENCE

When multiple pods are targeted, inject parallel (all at once) or serial (one after another).

parallel

Runtime and helper

Tunable
Description
Default

CONTAINER_RUNTIME

Container runtime on the target nodes. One of containerd, docker, crio.

containerd

SOCKET_PATH

Path to the container runtime socket on the target node. Set to match CONTAINER_RUNTIME.

/run/containerd/containerd.sock

RAMP_TIME

Wait period in seconds before and after the fault. Go to ramp time to read how it is applied.

0

Tunables that apply to every chaos fault are documented in common tunables for all faults.

SCOPE LATENCY TO ONE DEPENDENCY

Setting DESTINATION_HOSTS=db.example.svc or DESTINATION_PORTS=5432 adds latency only to that dependency. Mesh control plane, metrics, DNS, and other traffic stay fast, so you isolate the variable under test.

Configure for your container runtime

Set CONTAINER_RUNTIME and SOCKET_PATH to match the runtime on the target node:

CONTAINER_RUNTIME

SOCKET_PATH

containerd (default)

/run/containerd/containerd.sock

docker

/var/run/docker.sock

crio

/var/run/crio/crio.sock

Fault execution in brief

Configures the container's network interface to add a specified delay (with optional jitter) to outbound packets, optionally scoping the effect to only certain destination IPs, hosts, or ports so other traffic passes through unaffected.

Expected behavior during fault execution

  • Packets matching the filter are buffered and released after the configured delay. Round-trip times rise by NETWORK_LATENCY plus any JITTER variation.

  • TCP throughput drops in proportion to the latency increase (bandwidth-delay product). HTTP/2 and gRPC connections accommodate the delay, but each call takes correspondingly longer.

  • UDP traffic (DNS, QUIC) is delayed but not dropped. DNS lookups that previously took 5 ms now take 5 + NETWORK_LATENCY ms; clients with short DNS timeouts may consider the lookup failed.

  • At very high latencies (10+ seconds), TCP keepalive can fail and connections drop. Health probes can time out.

  • Service meshes with outlier detection on slow response times may eject the pod from upstream load-balancing pools.

WHEN THE FAULT ENDS

The delay is removed and the pod's network returns to normal immediately. Any in-flight delayed packets are released as soon as the configuration is torn down.

Signals to watch

Attach resilience probes to assert each layer:

  • Tail latency: Use a Prometheus probe on your p99 latency metric to confirm the increase matches the injected delay.

  • Client timeouts and retries: Use an HTTP probe for direct endpoint health; rising timeouts signal that the client is not budgeted for the delay.

  • Pod readiness: Use a Kubernetes probe to fail when the target pod oscillates NotReady due to probe timeouts.

Verify the fault execution effect

While the experiment is running, measure round-trip time and confirm the increase:

  1. Measure round-trip time from another pod.

    The reported RTT should increase by approximately NETWORK_LATENCY (plus any JITTER) on matched flows.

  2. Confirm application-level impact.

    time_total should reflect the added delay. Application timeouts shorter than NETWORK_LATENCY fail; longer ones succeed but with elevated tail latency.

Recovery and cleanup

  • End of duration: The delay configuration is removed automatically and latency returns to baseline within seconds.

  • Abort the experiment: Stopping the experiment from Chaos Studio triggers the same cleanup path.

  • Failed cleanup: If automated cleanup did not complete, restart the target pod to reset its network state.

Limitations

  • Serverless Kubernetes (EKS Fargate, ACI virtual nodes): These platforms do not allow the privileged access this fault needs. GKE Autopilot is supported once the one-time setup in Chaos on GKE Autopilot is in place.

  • Windows containers: This fault is supported on Linux pods only.

  • CNI plugins that bypass the pod's eth0: Some eBPF-based plugins route packets host-side and may not be affected by this fault.

  • hostNetwork pods: The fault would apply to the host interface and affect the entire node. It refuses to inject on hostNetwork: true pods.

Troubleshooting

Pod network latency experiment stays Pending or never starts in Harness Chaos Engineering

Inspect the chaos pods in the experiment namespace with kubectl describe pod -n . The most common causes are taints on the target node, insufficient resources, or a PodSecurity admission policy blocking privileged pods. Add the required tolerations to the experiment or run in a namespace with privileged Pod Security level.

No latency observed during pod-network-latency

The most common causes are: NETWORK_INTERFACE does not match the pod's interface (verify with kubectl exec -- ip link show); the filter is too narrow and matches no real traffic (broaden DESTINATION_IPS/HOSTS/PORTS); or the pod uses hostNetwork and the fault was refused. Run ping from another pod to the target pod IP and confirm whether matched flows are slower.

Connection to container runtime fails for pod-network-latency in Harness Chaos Engineering

The default SOCKET_PATH is /run/containerd/containerd.sock. For Docker, set CONTAINER_RUNTIME=docker and SOCKET_PATH=/var/run/docker.sock. For CRI-O, set CONTAINER_RUNTIME=crio and SOCKET_PATH=/var/run/crio/crio.sock.

Latency persists after pod-network-latency ends

Automated cleanup did not complete. Restart the target pod to reset its network state. If the issue recurs, capture the chaos pod logs from the experiment namespace before the next run and share them with Harness support.

Related faults

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