Skip to main content

Pod JVM method exception

Last updated on

Pod JVM method exception is a Kubernetes pod-level chaos fault that causes a specific Java method in a JVM running in a target container to throw a configurable exception on every invocation for a configurable duration. Only the named method is affected; all other code paths run normally. When the fault ends, the method returns to its normal behavior immediately.

Use this fault to test how callers and dependents react when a specific method starts throwing: a database wrapper that raises a connection error, a third-party SDK call that fails, or a business-logic method that hits an invariant.

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:

  • Caller exception handling: Does the calling code catch the exception, propagate it, or crash the thread?
  • Retry semantics: Does the caller honor a retry budget, or do retries amplify load on the rest of the system?
  • Circuit breaker tripping: Does a circuit breaker around the failing method open after the configured failure threshold and short-circuit subsequent calls?
  • Trace and log coverage: Does the failure surface in tracing and logs with enough context to be diagnosable in production?
  • Compensating transactions: For multi-step business operations, do rollback paths complete cleanly when one step fails?

Prerequisites​

  • Kubernetes version: 1.21 or later. Go to What's supported to confirm distribution support.
  • Target pod is Running: The Java application pod is in the Running state.
  • Java agent attach available: The Java process allows agent attach. Utilities such as ps, pgrep, and bash are present in the container, and the JVM is not built with a restricted runtime that strips attach modules.
  • Privileged pods allowed: The cluster lets you schedule privileged pods in the chaos namespace. GKE Autopilot supports this fault but requires the one-time setup in Chaos on GKE Autopilot; other locked-down distributions may need similar exemptions.
  • Container runtime access: The chaos pod can reach the container runtime socket on the target node (/run/containerd/containerd.sock, /var/run/docker.sock, or /var/run/crio/crio.sock).
  • Workload selector defined: The chaos experiment knows the target workload by kind, namespace, and either names or labels.
JVM chaos uses the Byteman agent

This fault attaches a Byteman agent to the target JVM over BYTEMAN_PORT. The port must be reachable from the chaos pod and must not be in use by the application.

Supported environments​

PlatformSupport status
Amazon EKSSupported
Azure AKSSupported
Google GKESupported
Red Hat OpenShiftSupported
RancherSupported
VMware TanzuSupported
Self-managed Kubernetes (CNCF-certified)Supported
GKE AutopilotSupported with Autopilot setup
EKS Fargate, ACI virtual nodesNot supported (no access to container runtime sockets)

Permissions required​

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

Resource (apiGroup)VerbsWhy it is needed
pods ("")get, list, create, delete, deletecollection, patch, updateDiscover target pods and run the chaos pod on the same node
pods/log ("")get, list, watchStream chaos pod logs for status and debugging
deployments, statefulsets, replicasets, daemonsets (apps)get, listResolve the target workload to the pods it owns
events ("")get, list, create, patch, updateRecord fault progress as Kubernetes events
jobs (batch)get, list, create, delete, deletecollectionRun 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 JVM method exception to an experiment in Chaos Studio. Defaults are shown for reference.

Required parameters

TunableDescriptionDefault
CLASSFully qualified class name containing the target method (for example com.example.payments.PaymentService).(required)
METHODName of the method to throw the exception from.(required)
EXCEPTIONFully qualified exception class to throw (for example java.lang.IllegalStateException).(required)

Chaos parameters

TunableDescriptionDefault
TOTAL_CHAOS_DURATIONDuration of the fault in seconds.60

JVM

TunableDescriptionDefault
BYTEMAN_PORTPort on which the Byteman agent listens inside the container. Must not conflict with any port already in use.9091
JAVA_HOMEAbsolute path to the Java installation inside the container. Empty auto-detects from PATH.""

Targeting

TunableDescriptionDefault
TARGET_PODSComma-separated list of pod names to target. Empty selects from the workload's pods using POD_AFFECTED_PERCENTAGE.""
TARGET_CONTAINERContainer in the pod running the JVM. Empty targets the first container in the pod spec.""
NODE_LABELLabel selector to filter target pods by the node they run on. Empty disables node-based filtering.""
POD_AFFECTED_PERCENTAGEPercentage of the workload's pods to target. 0 means one pod.0
SEQUENCEWhen multiple pods are targeted, inject parallel (all at once) or serial (one after another).parallel

Runtime and helper

TunableDescriptionDefault
CONTAINER_RUNTIMEContainer runtime on the target nodes. One of containerd, docker, crio.containerd
SOCKET_PATHPath to the container runtime socket on the target node. Set to match CONTAINER_RUNTIME./run/containerd/containerd.sock
RAMP_TIMEWait period in seconds before and after the fault. Go to ramp time to read how it is applied.0

Common pod selection tunables (TARGET_WORKLOAD_KIND, TARGET_WORKLOAD_NAMESPACE, TARGET_WORKLOAD_NAMES, TARGET_WORKLOAD_LABELS) are documented in common pod fault tunables. Tunables that apply to every fault are documented in common tunables for all faults.

Pick the right exception type

Choose an exception that the caller can plausibly receive in production (for example java.sql.SQLException for a database wrapper, java.io.IOException for a network helper). Picking an unrelated exception type often surfaces uncaught-exception bugs that would not happen in real failures.

Configure for your container runtime​

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

CONTAINER_RUNTIMESOCKET_PATH
containerd (default)/run/containerd/containerd.sock
docker/var/run/docker.sock
crio/var/run/crio/crio.sock

Fault execution in brief​

Attaches a Java agent to the target JVM and instruments CLASS.METHOD so that each invocation throws an instance of EXCEPTION for TOTAL_CHAOS_DURATION seconds.

Expected behavior during fault execution​

  • Every call to the named method raises the configured exception. Other methods run normally.
  • Direct callers surface the failure as caught exceptions, error responses, or queued retries depending on the framework.
  • Tracing systems show the method span ending in error; downstream calls that depended on the method's return value do not happen for failed invocations.
  • Error dashboards see a spike in the configured exception type.
When the fault ends

The method returns to its normal behavior immediately. Cached state (open circuits, exhausted retry budgets) in callers may take additional time to reset.

Signals to watch​

Attach resilience probes to assert each layer:

  • Method-level error rate: Use a Prometheus probe on the method's error counter to confirm the injection took effect.
  • Caller error rate: Use an HTTP probe against endpoints that exercise the method to detect 5xx spikes.
  • Application logs: Use a command probe to grep container logs for the injected exception's class name.

Verify the fault execution effect​

While the experiment is running, confirm the method is throwing:

  1. Exercise the method from a client.

    kubectl run -n <namespace> tester --image=nicolaka/netshoot --rm -it -- \
      curl -s http://<service>:<port>/<endpoint-that-calls-the-method>

    The response should reflect the failure.

  2. Confirm the exception in logs.

    kubectl logs -n <namespace> <target-pod> --tail=200 | grep <EXCEPTION>

    The configured exception class should appear in stack traces.

Recovery and cleanup​

  • End of duration: The method returns to its normal behavior automatically.
  • Abort the experiment: Stopping the experiment from Chaos Studio triggers the same cleanup path.
  • Stuck state: If a downstream circuit breaker stays open or a retry budget is exhausted, follow the application's recovery procedure or restart the pod.

Limitations​

  • Serverless Kubernetes (EKS Fargate, ACI virtual nodes): These platforms do not expose container runtime sockets and reject the privileged access the 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.
  • Non-JVM processes: This fault targets a Java process.
  • Inlined or intrinsified methods: Methods that the JIT compiler has inlined may not be interceptable; consider running with -XX:-Inline for verification.
  • Method overloads: Only the method name is matched. If multiple overloads share a name, all are affected for the duration.

Troubleshooting​

Pod JVM method exception experiment stays Pending or never starts in Harness Chaos Engineering

Inspect the chaos pods in the experiment namespace with kubectl describe pod -n <chaos-namespace>. The most common causes are taints on the target node that the chaos pods do not tolerate, insufficient resources, or a PodSecurity admission policy blocking privileged pods. Add the required tolerations or run in a namespace with privileged Pod Security level.

No exception observed during pod-jvm-method-exception

The most common causes are: CLASS or METHOD does not match (verify the fully qualified class name and case-sensitive method name); the method is JIT-inlined and not interceptable; the wrong container is targeted (set TARGET_CONTAINER explicitly); or JAVA_HOME is not detectable. Re-run with EXCEPTION set to a common type like java.lang.IllegalStateException to confirm the path is working.

Connection to container runtime fails for pod-jvm-method-exception 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.