CF app network latency
CF app network latency is a Cloud Foundry chaos fault that adds networkLatency milliseconds of delay (with optional jitter) on the egress traffic of one or more app instances of app in organization/space. You can restrict the delay to specific destination hosts, IP ranges, source ports, or destination ports. The fault lasts for duration seconds.
Use this fault to simulate a slow downstream dependency at the network layer, validate timeouts and retries inside the app, and quantify the end-to-end latency cost contributed by a single slow link.
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
- Slow downstream rehearsal: Simulate a slow database or third-party API and validate the app's timeout configuration.
- Tail-latency budget: Measure how an extra 100/500/1000 ms downstream impacts the user-visible P99.
- Geo-latency simulation: Approximate cross-region call latency to test caching and locality decisions.
- Targeted partition: Slow traffic only to a specific dependency without affecting the rest of the app.
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, andBOSH_*credentials configured. - Target identifiers: You know the
organization,space,app, and theboshDeployment. - Network interface: You know the interface name inside the container (typically
eth0). - Destinations: You know the host(s), IP range(s), or port(s) you want to slow down. Leave blank to affect all egress.
Supported environments
| Platform | Support status |
|---|---|
| Cloud Foundry (TAS, PCF, open-source) running on BOSH-managed Diego cells | 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 |
| Apply traffic-shaping rules inside the target container's namespace | 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 | App whose egress traffic is delayed. | (required) |
Chaos parameters
| Tunable | Description | Default |
|---|---|---|
networkLatency | Added latency in milliseconds. | 2000 |
jitter | Random variation around networkLatency, in milliseconds. | 0 |
networkInterface | Network interface inside the container. | eth0 |
destinationHosts | Comma-separated list of hostnames to affect. Leave empty to affect all egress. | "" |
destinationIPs | Comma-separated list of destination IPs or CIDRs to affect. | "" |
sourcePorts | Comma-separated list of source ports to affect (egress from these ports). | "" |
destinationPorts | Comma-separated list of destination ports to affect. | "" |
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), and installs a traffic-shaping rule on networkInterface inside the container's network namespace that delays packets matching the configured destinations/ports by networkLatency ms (±jitter). The rule is removed when duration elapses.
Expected behavior during fault execution
- TCP round-trip times to the affected destinations rise by approximately
networkLatencyms. - Caller-side response times reflect the added delay; retries may stack if timeouts are too short.
- Throughput typically falls in proportion to the added round-trip time.
- After the fault ends, latency returns to baseline.
Signals to watch
- App latency: Use an HTTP probe on a public route.
- Downstream metrics: Inspect the app's outbound call metrics (response time histograms) for the affected dependency.
Recovery and cleanup
- The traffic-shaping rule is removed at the end of
duration. - If the experiment is aborted, the fault still attempts to remove the rule before exiting.
Limitations
- Operates on the egress side of the affected instance only. Ingress traffic is not delayed.
- Without a destination filter (
destinationHosts,destinationIPs, or port filters), ALL egress is affected, which may also slow control-plane health checks.
Troubleshooting
CF app network latency: no observable delay in Harness Chaos Engineering
Confirm networkInterface matches the interface inside the container (cf ssh <app> -c 'ip a'). Confirm destinationHosts or destinationIPs actually match the traffic you want to slow.
App health checks fail during the experiment
Without destination filters, control-plane traffic is also delayed. Add destinationHosts or destinationIPs to scope the delay to your dependency only.
Common configurations
Slow only one downstream
apiVersion: litmuchaos.io/v1alpha1
kind: LinuxFault
metadata:
name: cf-app-network-latency
labels:
name: app-network-latency
spec:
cfAppNetworkChaos/inputs:
duration: 60s
deploymentModel: model-2
faultInjectorLocation: vSphere
app: cf-app
organization: dev-org
space: dev-space
boshDeployment: cf
networkInterface: eth0
networkLatency: 500
jitter: 100
destinationHosts: payments-api.internal
CF secrets
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.envfile- 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-api-endpoint |
| CF_USERNAME | USERNAME | username |
| CF_PASSWORD | PASSWORD | password |
| UAA_SERVER_ENDPOINT | UAA_SERVER_ENDPOINT | uaa-server-endpoint |
| BOSH_CLIENT | BOSH_CLIENT | bosh-client |
| BOSH_CLIENT_SECRET | BOSH_CLIENT_SECRET | bosh-client-secret |
| BOSH_CA_CERT | BOSH_CA_CERT | bosh-ca-cert |
| BOSH_ENVIRONMENT | BOSH_ENVIRONMENT | bosh-environment |
vSphere secrets
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 |
Related faults
- CF app network loss: Drop packets instead of delaying them.
- CF app JVM method latency: Add latency at a specific Java method instead of the network.