Linux JVM method latency

Add latency to a target class and method in a Java process on a Linux machine so you can test how the application behaves when an internal method slows down.

Linux JVM method latency is a chaos fault that uses Byteman to add LATENCY milliseconds of delay to every invocation of CLASS.METHOD in the target Java process for DURATION, then removes the rule. The target Java process is selected by PID, by STARTUP_COMMAND, or by attaching to a running Byteman agent on PORT. The fault runs through the Linux Chaos Infrastructure (LCI) systemd service installed on the target VM.

Use this fault to test how a Java workload behaves when a hot method gets slow: whether the caller honors its own timeout, whether thread-pool exhaustion appears, whether circuit breakers fire, and whether monitoring detects the in-JVM slowdown within the alerting SLA.

RUN YOUR FIRST EXPERIMENT

If you have not installed the Linux Chaos Infrastructure yet, go to Linux Chaos Infrastructure to install the agent and connect the VM to the control plane.

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Use cases

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

• Method slowdown tolerance: When CLASS.METHOD slows by LATENCY milliseconds, do request handlers stay inside their p99 SLA?

• Thread-pool starvation: Do worker pools or async executors back up when a hot method blocks?

• Caller timeouts: Do callers honor their own timeouts, or do they hold the thread until the method returns?

• Monitoring fidelity: Do alerts on method-level latency, queue depth, and request latency fire within the alerting SLA?

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Prerequisites

• Linux Chaos Infrastructure installed: The linux-chaos-infrastructure systemd service is active on the target VM and the infrastructure is in CONNECTED state. Go to Linux Chaos Infrastructure to install it.

• Target JVM identifiable: Provide one of PID or STARTUP_COMMAND, or ensure a Byteman agent is already listening on PORT.

• JAVA_HOME reachable: Set JAVA_HOME if it is not on the LCI service environment.

• Target class loaded: The JVM must have CLASS loaded and the matching METHOD defined.

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Supported environments

The fault has been tested on the following Linux distributions. Go to Linux fault requirements to see the full compatibility matrix.

Platform	Support status
Ubuntu 16+, Debian 10+	Supported
CentOS 7+, RHEL 7+, Fedora 30+	Supported
openSUSE LEAP 15.4+ / SUSE Linux Enterprise 15+	Supported
JVM versions	OpenJDK 8, 11, 17, 21 (any JVM compatible with Byteman)

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Permissions required

This fault is classified as a Basic Linux fault. It runs with the privileges of the Linux Chaos Infrastructure systemd service (root user and root user group) on the target VM. The LCI service must have permission to attach to the target Java process. No cloud credentials are needed.

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Fault tunables

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

Required parameters

Tunable	Description	Default
CLASS	Fully qualified class name containing the target method.	(required)
METHOD	Method name within CLASS to delay.	(required)

JVM selectors (provide one or rely on PORT)

Tunable	Description	Default
PID	PID of the target Java process. Set to 0 to fall back to STARTUP_COMMAND or PORT.	0
STARTUP_COMMAND	Substring of the Java process command line used to identify the target.	""
PORT	Port of the Byteman agent.	9091
JAVA_HOME	Path to the JDK used by the target JVM.	""

Chaos parameters

Tunable	Description	Default
DURATION	Total duration of the fault. Accepts [hours]h[minutes]m[seconds]s format.	30s
LATENCY	Latency to inject per method call, in milliseconds.	2000
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 fault are documented in common tunables for all faults.

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Fault execution in brief

Attaches Byteman to the target JVM on PORT, installs a rule that sleeps LATENCY milliseconds before CLASS.METHOD executes (per invocation) for DURATION, then removes the rule.

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Expected behavior during fault execution

• Every invocation of CLASS.METHOD takes LATENCY milliseconds longer than usual for the duration of the fault.

• Request handlers that depend on the method are delayed; thread-pool occupancy rises.

• Tail latency (p99) for endpoints exercising the method shifts upward by approximately LATENCY.

• Callers that have shorter timeouts than LATENCY see clean timeout errors.

• After the duration ends, the Byteman rule is removed and the method runs at baseline speed.

WHEN THE FAULT ENDS

The chaos pod removes the Byteman rule. The next invocation of the method runs at baseline speed; in-flight invocations complete after their delay.

Signals to watch

Attach resilience probes to assert each layer:

• Method latency: Use a Prometheus probe on application method-level latency metrics.

• Request latency: Use an HTTP probe on a user-visible endpoint that exercises the method.

• Thread-pool occupancy: Use a Prometheus probe on jvm_threads_state or a custom thread-pool gauge.

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Verify the fault execution effect

1. Trigger the method via a user-visible endpoint.

   curl -w '%{time_total}\n' -o /dev/null -s https://<app>/<endpoint>

   Latency for the endpoint should rise by approximately LATENCY (per method call) during the chaos window.

2. Inspect Byteman state.

   sudo $JAVA_HOME/bin/bmtool -p <PORT> -l

3. Inspect Linux Chaos Infrastructure logs.

   sudo journalctl -u linux-chaos-infrastructure -n 100 --no-pager

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Recovery and cleanup

• End of duration: The chaos pod removes the Byteman rule when DURATION elapses.

• Abort the experiment: Stopping the experiment from Chaos Studio also removes the rule.

• Manual recovery: If the rule survives an abort, remove it with sudo $JAVA_HOME/bin/bmtool -p <PORT> -u <rule>.

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Limitations

• Per-invocation delay: LATENCY is added per invocation; methods called in tight loops will accumulate large delays.

• Method visibility: The target method must be defined on a loaded class; lazy-loaded classes are not affected until first use.

• Overload resolution: Byteman matches on method name; all overloads are delayed.

• Byteman dependency: The target JVM must allow Byteman attachment.

• Single JVM scope: Each fault run targets one Java process.

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Troubleshooting

Linux JVM method latency fault did not slow the method in Harness Chaos Engineering

Confirm CLASS is the fully qualified name and that METHOD is defined on a loaded class. Trigger the method explicitly and measure the response time with curl. Verify Byteman attached with sudo bmtool -p -l.

Latency accumulated faster than expected

LATENCY is added per invocation. If the method is called many times per request, total request latency is approximately N x LATENCY. Reduce LATENCY or instrument the call site to see the actual invocation count.

Latency persisted after the experiment ended

If the Byteman rule was not removed, list with sudo bmtool -p -l and remove with -u . If the rule cannot be removed, restart the target JVM to clear injected rules.

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Related faults

• Linux JVM method exception: Throw an exception from the method instead of delaying it.

• Linux JVM modify return: Override the return value instead of delaying.

• Linux network latency: Add latency at the network layer instead of inside the JVM.