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Pod JVM SQL latency

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Pod JVM SQL latency is a Kubernetes pod-level chaos fault that adds a configurable delay to JDBC calls from a JVM running in a target container, scoped to a chosen table and SQL operation, for a configurable duration. Only matched calls are slowed; unrelated queries and other code paths run at normal speed. When the fault ends, JDBC calls return to baseline latency immediately.

Use this fault to test how a Java service behaves when the database becomes slow on a specific code path: a heavy join, a write that contends on row locks, or a read replica falling behind.

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:

  • Driver timeout sensitivity: When a SELECT takes 2 seconds instead of 20 ms, does the application surface the slow query or block worker threads?
  • Connection-pool saturation: Does the application's connection pool back-pressure correctly or starve under slow queries?
  • Write-path back-pressure: Slow INSERT or UPDATE and see whether the application throttles producers or queues writes in memory.
  • Reporting tail latency: Slow SELECT only on reporting tables and verify whether the reporting paths cope.
  • Circuit breaker behavior: Does a circuit breaker around the slow operation trip and recover correctly when the fault ends?

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.
  • JDBC driver in classpath: The target JVM uses a supported JDBC driver matching SQL_DATA_ACCESS_FRAMEWORK.
  • 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 SQL latency to an experiment in Chaos Studio. Defaults are shown for reference.

SQL filters

TunableDescriptionDefault
TABLETarget database table name. Empty matches all tables.""
SQL_OPERATIONSQL operation to target. Common values: SELECT, INSERT, UPDATE, DELETE. Empty matches all operations.""
SQL_DATA_ACCESS_FRAMEWORKJDBC driver framework identifier. For example MYSQL8."MYSQL8"
TRANSACTION_PERCENTAGEPercentage of matched SQL statements to delay, between 0 and 100. 0 delays none; 100 delays every match.0

Chaos parameters

TunableDescriptionDefault
LATENCYDelay to add to each matched statement, in milliseconds.2000
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.

Match operation to scenario

For read-heavy workloads, target SELECT. For ingest paths, target INSERT and UPDATE. Scoping the slow operation matches a production failure mode and keeps the blast radius small.

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 intercepts JDBC statements matching TABLE and SQL_OPERATION for the configured SQL_DATA_ACCESS_FRAMEWORK to add LATENCY milliseconds to each matched call on the configured percentage, for TOTAL_CHAOS_DURATION seconds.

Expected behavior during fault execution​

  • Matched SQL statements take longer by approximately LATENCY ms. Other statements and unrelated tables run normally.
  • Caller-side metrics (request latency, queue depth, connection-pool waiters) rise to reflect the added delay.
  • Clients with statement timeouts shorter than LATENCY cancel the call and may retry.
  • Thread-pool-bound applications saturate quickly if many concurrent callers wait on the slow operation.
  • Tracing systems show the matched JDBC span growing by LATENCY ms.
When the fault ends

JDBC calls return to baseline latency immediately. Calls in flight finish at the delayed time and then the system returns to normal.

Signals to watch​

Attach resilience probes to assert each layer:

  • Driver-level latency: Use a Prometheus probe on jdbc.connections duration or your APM's SQL latency metric.
  • Caller timeouts: Use an HTTP probe against endpoints that read or write to the targeted table.
  • Pod readiness: Use a Kubernetes probe to fail when the target pod oscillates NotReady.

Verify the fault execution effect​

While the experiment is running, confirm operations are slower:

  1. Time a request that exercises the matched operation.

    kubectl run -n <namespace> tester --image=nicolaka/netshoot --rm -it -- \
      curl -w "time=%{time_total}\n" -o /dev/null -s http://<service>:<port>/<endpoint>

  2. Confirm in tracing.

    The JDBC span for the matched operation should be approximately LATENCY ms longer than its baseline.

Recovery and cleanup​

  • End of duration: JDBC calls return to baseline latency automatically.
  • Abort the experiment: Stopping the experiment from Chaos Studio triggers the same cleanup path.
  • Stuck threads: If the application is wedged because of saturated thread or connection pools, 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 and non-JDBC workloads: This fault targets JDBC drivers inside a JVM.
  • ORM caching: ORMs that cache results may continue to serve queries from cache, bypassing the slowdown on those calls.

Troubleshooting​

Pod JVM SQL latency 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 latency observed during pod-jvm-sql-latency

The most common causes are: TABLE does not match the table name used by the application; SQL_OPERATION does not match the executed verb; SQL_DATA_ACCESS_FRAMEWORK does not match the driver in classpath; or TRANSACTION_PERCENTAGE is 0 (default). Re-run with TRANSACTION_PERCENTAGE=100 and empty filters to confirm the path is working.

Connection to container runtime fails for pod-jvm-sql-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.