CF app JVM method exception

Make a specific JVM method throw an exception inside a Cloud Foundry app instance so you can test how callers handle synchronous failures.

CF app JVM method exception is a Cloud Foundry chaos fault that forces a specific JVM method (class.method) inside a running Java app to throw the exception class you specify in exception. The fault lasts for duration seconds, after which the method behaves normally again.

Use this fault to validate the application's error-handling paths: try/catch coverage, exception-mapping, retry budgets, dead-letter queues, and circuit-breaker trips. It is also useful for testing how upstream consumers handle a known synchronous failure pattern.

RUN YOUR FIRST EXPERIMENT

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

Use cases

Catch-block coverage: Confirm exceptions raised by a key method are caught and mapped to the expected user-visible response.
Retry budgets: Validate the caller does not retry indefinitely on a permanent-looking exception.
Circuit-breaker behavior: Confirm the breaker opens after the configured threshold.
Observability: Verify the exception surfaces in logs and metrics with the right severity and tags.

Before you begin

Chaos infrastructure: A Linux chaos infrastructure (LCI) installed in one of the supported deployment models.
CF and BOSH credentials: The LCI host has CF_*, UAA_SERVER_ENDPOINT, and BOSH_* credentials configured.
Target identifiers: You know the organization, space, app, and the boshDeployment.
Java app: The target app exposes a JVM agent on port (default 9091).
Method signature: You know the fully qualified class name and method name to target. Overloaded methods are matched by name; restrict the experiment in test environments to avoid false targets.

Supported environments

Platform

Support status

Java apps deployed to Cloud Foundry

Supported

Non-Java workloads

Not supported

Permissions required

Action

Requirement

List apps the CF user can access

SpaceDeveloper, SpaceAuditor, OrgManager, or OrgAuditor; scopes cloud_controller.read or cloud_controller.admin

List BOSH deployments

BOSH user with bosh.read scope

SSH to a Diego cell via BOSH

BOSH UAA token with bosh.ssh or bosh.admin scope

Attach the JVM agent to the target container

Operator with sudo or root on the cell host

Authentication

Layer

Where to provide

Tunables

Cloud Foundry API + BOSH director

/etc/linux-chaos-infrastructure/cf.env on the LCI host

CF_API_ENDPOINT, CF_USERNAME, CF_PASSWORD, UAA_SERVER_ENDPOINT, BOSH_CLIENT, BOSH_CLIENT_SECRET, BOSH_CA_CERT, BOSH_ENVIRONMENT

vSphere (only when faultInjectorLocation: vSphere)

/etc/linux-chaos-infrastructure/vsphere.env

GOVC_URL, GOVC_USERNAME, GOVC_PASSWORD, GOVC_INSECURE, VM_NAME, VM_USERNAME, VM_PASSWORD

Fault tunables

Required parameters

Tunable

Description

Default

deploymentModel

LCI placement model. One of model-1 or model-2.

(required)

organization

CF organization that owns the app.

(required)

space

CF space within the organization.

(required)

app

Java app whose method is targeted.

(required)

class

Fully qualified class name (for example, com.example.OrderService).

(required)

method

Method on class to instrument.

(required)

exception

Fully qualified exception class to throw (for example, java.lang.RuntimeException).

(required)

Chaos parameters

Tunable

Description

Default

port

JVM agent port inside the container.

9091

javaHome

Value of JAVA_HOME. Not required if the Java binary is on the container's PATH.

""

instanceAffectedPercentage

Percentage of instances to target. 0 targets exactly one.

0

boshDeployment

BOSH deployment name. Required for deploymentModel: model-2.

""

faultInjectorLocation

local or vSphere. Required for deploymentModel: model-2.

local

faultInjectorPort

Local port used by the fault-injector.

50320

duration

Total chaos duration.

30s

skipSSLValidation

Skip SSL validation when calling CF APIs.

false

rampTime

Wait period in seconds before and after the fault.

0

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

Fault execution in brief

Authenticates to Cloud Foundry and BOSH, locates the target app instance(s), attaches an agent to the JVM via the debug port, and installs a rule that makes every call to class.method throw an instance of exception. The rule is removed when duration elapses.

Expected behavior during fault execution

Every invocation of the targeted method throws the configured exception until the rule is removed.
Callers experience whatever error path your application defines for that exception (HTTP 500, mapped 4xx, retry-then-fail, circuit-breaker open, and so on).
After the fault ends, the method returns to its normal implementation.

Signals to watch

Caller-side error rate: Use an HTTP probe on an endpoint that calls the targeted method.
Exception logs: Confirm the configured exception appears in the app's logs with the expected severity.

Recovery and cleanup

The instrumentation is removed when duration elapses, restoring normal behavior.
If the experiment is aborted, the fault still attempts to remove the rule before exiting.

Limitations

Matches methods by name only. Overloaded methods on the same class throw the exception regardless of signature.
The fault does not synthesise a stack trace; the exception originates inside the JVM agent.

Troubleshooting

CF app JVM method exception fails with 'class or method not found' in Harness Chaos Engineering

Confirm the fully qualified class name (with package) and method name match the loaded code exactly. Class names are case-sensitive. Use cf ssh -c 'jcmd 1 GC.class_histogram' to inspect what is loaded.

Method still returns normally after the fault starts

The targeted method may not have been called during the chaos window, or it was JIT-inlined before the agent attached. Generate traffic through the endpoint that calls the method, or restart the app instance before re-running.

Common configurations

Throw a custom exception

apiVersion: litmuchaos.io/v1alpha1
kind: LinuxFault
metadata:
  name: cf-app-jvm-method-exception
  labels:
    name: app-jvm-method-exception
spec:
  cfAppJVMChaos/inputs:
    duration: 30s
    deploymentModel: model-2
    faultInjectorLocation: vSphere
    app: cf-app
    organization: dev-org
    space: dev-space
    boshDeployment: cf
    class: com.example.OrderService
    method: placeOrder
    exception: com.example.OrderRejectedException

The following Cloud Foundry secrets reside on the same machine where the chaos infrastructure is executed. These secrets are provided in the /etc/linux-chaos-infrastructure/cf.env file in the following format:

CF_API_ENDPOINT=XXXXXXXXXXXXXXXXXXX
CF_USERNAME=XXXXXXXXXXXXXXXXXXXXXXX
CF_PASSWORD=XXXXXXXXXXXXXXXXXXXXXXX
UAA_SERVER_ENDPOINT=XXXXXXXXXXXXXXX
BOSH_CLIENT=XXXXXXXXXXXXXXXXXXXXXXX
BOSH_CLIENT_SECRET=XXXXXXXXXXXXXXXX
BOSH_CA_CERT=XXXXXXXXXXXXXXXXXXXXXX
BOSH_ENVIRONMENT=XXXXXXXXXXXXXXXXXX

If the secrets file is not provided, the secrets are attempted to be derived from environment variables and the config file by the fault-injector.

ENV name

Description

Example

CF_API_ENDPOINT

API endpoint for the CF setup

https://api.system.cf-setup.com

CF_USERNAME

Username for the CF user

username

CF_PASSWORD

Password for the CF user

password

UAA_SERVER_ENDPOINT

API endpoint for the UAA server for the CF setup

https://uaa.system.cf-setup.com

BOSH_CLIENT

Used by the bosh CLI, the BOSH client

admin

BOSH_CLIENT_SECRET

Used by the bosh CLI, the BOSH client secret

UBu9Fu3oW35sO6fw12auPH76gsRTy7

BOSH_CA_CERT

Used by the bosh CLI, the file path for BOSH CA certificate

/root/root_ca_certificate

BOSH_ENVIRONMENT

Used by the bosh CLI, the BOSH environment

bosh.corp.local

Fault injector ENVs and config file

If /etc/linux-chaos-infrastructure/cf.env file is not provided, fault-injector attempts to derive the secrets from environment variables or a configuration file. Any secret that is re-declared will be overridden in the following order of decreasing precedence:

/etc/linux-chaos-infrastructure/cf.env file
Environment variables
Configuration file

The configuration file should be provided at /etc/linux-chaos-infrastructure/cf-fault-injector.yaml:

cf-api-endpoint: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
username: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
password: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
uaa-server-endpoint: XXXXXXXXXXXXXXXXXXXXXXXXXX
bosh-client: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
bosh-client-secret: XXXXXXXXXXXXXXXXXXXXXXXXXXX
bosh-ca-cert: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
bosh-environment: XXXXXXXXXXXXXXXXXXXXXXXXXXXXX

A mapping between all the three formats for providing the secrets is as follows:

cf.env

ENV

cf-fault-injector.yaml

CF_API_ENDPOINT

cf-api-endpoint

CF_USERNAME

USERNAME

username

CF_PASSWORD

PASSWORD

password

UAA_SERVER_ENDPOINT

uaa-server-endpoint

BOSH_CLIENT

bosh-client

BOSH_CLIENT_SECRET

bosh-client-secret

BOSH_CA_CERT

bosh-ca-cert

BOSH_ENVIRONMENT

bosh-environment

These secrets are provided only if vSphere is used as the deployment platform for CF.

The following vSphere secrets reside on the same machine where the chaos infrastructure is executed. These secrets are provided in the /etc/linux-chaos-infrastructure/vsphere.env file in the following format:

GOVC_URL=XXXXXXXXXXXXXXXXXXXXXX
GOVC_USERNAME=XXXXXXXXXXXXXXXXX
GOVC_PASSWORD=XXXXXXXXXXXXXXXXX
GOVC_INSECURE=XXXXXXXXXXXXXXXXX
VM_NAME=XXXXXXXXXXXXXXXXXXXXXXX
VM_USERNAME=XXXXXXXXXXXXXXXXXXX
VM_PASSWORD=XXXXXXXXXXXXXXXXXXX

ENV Name

Description

Notes

GOVC_URL

Endpoint for vSphere

For example, 192.168.214.244

GOVC_USERNAME

Username for the vSphere user

For example, username

GOVC_PASSWORD

Password for the vSphere user

For example, password

GOVC_INSECURE

Skip SSL validation for govc commands

For example, true

VM_NAME

Name of the vSphere VM where the fault-injector utility is installed

For example, cf-vm

VM_USERNAME

Username for the VM guest user

For example, root

VM_PASSWORD

Password for the VM guest user

For example, password

CF app JVM method latency: Make the same method slow instead of failing.
CF app JVM modify return: Make the method return a different value instead of throwing.

Last updated 7 days ago

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Use cases

Before you begin

Supported environments

Permissions required

Authentication

Fault tunables

Fault execution in brief

Expected behavior during fault execution

Signals to watch

Recovery and cleanup

Limitations

Troubleshooting

Common configurations

Throw a custom exception

Fault injector ENVs and config file

Related faults