extension-jvm

README

Steadybit extension-jvm

This Steadybit extension provides a jvm instance discovery and the various actions for jvm instances targets.

Learn about the capabilities of this extension in our Reliability Hub.

Configuration

Environment Variable	Helm value	Meaning	Required	Default
STEADYBIT_EXTENSION_RUNTIME	container.runtime	The container runtime to user either docker, containerd or cri-o. Will be automatically configured if not specified.	yes	(auto)
STEADYBIT_EXTENSION_SOCKET	containerRuntimes.(docker/containerd/cri-o).socket	The socket used to connect to the container runtime. Will be automatically configured if not specified.	yes	(auto)
STEADYBIT_EXTENSION_CONTAINERD_NAMESPACE		The containerd namespace to use.	yes	k8s.io
STEADYBIT_EXTENSION_RUNC_ROOT	containerRuntimes.(docker/containerd/cri-o).runcRoot	The runc root to use.	yes	(auto)
STEADYBIT_EXTENSION_RUNC_DEBUG		Activate debug mode for run.
STEADYBIT_EXTENSION_JVM_ATTACHMENT_ENABLED		is jvm attachment enabled	no	true
STEADYBIT_EXTENSION_JAVA_AGENT_ATTACHMENT_PORT		java agent attachment port	no	8095
STEADYBIT_EXTENSION_CONTAINER_ADDRESS		public ip of the extension	no
STEADYBIT_EXTENSION_DISCOVERY_ATTRIBUTES_EXCLUDES_JVM	discovery.attributes.excludes.jvm	List of Target Attributes which will be excluded during discovery. Checked by key equality and supporting trailing "*"	false

The extension supports all environment variables provided by steadybit/extension-kit.

When installed as linux package this configuration is in/etc/steadybit/extension-jvm.

Needed capabilities

The capabilities needed by this extension are: (which are provided by the helm chart)

• SYS_ADMIN
• SYS_RESOURCE
• SYS_PTRACE
• KILL
• NET_ADMIN
• DAC_OVERRIDE
• SETUID
• SETGID
• AUDIT_WRITE

Needed access to the java process

To be able to discover we need access to the java process. This is done by using the attach mechanism of the JVM. This is a standard mechanism and is used by many other tools. You may see a warning in the logs of the JVM that the extension is attaching to the JVM. This is normal and expected. It will look like this:

WARNING: A Java agent has been loaded dynamically (...javaagent-init.jar)
WARNING: Dynamic loading of agents will be disallowed by default in a future release

To avoid this warning or be able to use this extension in future java releases you can use the -XX:+EnableDynamicAgentLoading flag in your JVM commandline to be able to load the javaagent dynamically.

Needed configuration for Spring Boot

In order to discover the spring boot applications correctly you need to enable some JMX beans and set an application name. Add these to your application.properties:

spring.application.name=my-application-name
spring.jmx.enabled=true
management.endpoints.jmx.exposure.include=beans,mappings

Installation

Kubernetes

Detailed information about agent and extension installation in kubernetes can also be found in our documentation.

Recommended (via agent helm chart)

All extensions provide a helm chart that is also integrated in the helm-chart of the agent.

The extension is installed by default when you install the agent.

You can provide additional values to configure this extension.

--set extension-jvm.container.runtime={{YOUR-CONTAINER-RUNTIME}} \

Additional configuration options can be found in the helm-chart of the extension.

Alternative (via own helm chart)

If you need more control, you can install the extension via its dedicated helm-chart.

helm repo add steadybit-extension-jvm https://steadybit.github.io/extension-jvm
helm repo update
helm upgrade steadybit-extension-jvm \
    --install \
    --wait \
    --timeout 5m0s \
    --create-namespace \
    --namespace steadybit-agent \
    --set container.runtime=docker \
    steadybit-extension-jvm/steadybit-extension-jvm

Linux Package

Please use our agent-linux.sh script to install the extension on your Linux machine. The script will download the latest version of the extension and install it using the package manager.

After installing, configure the extension by editing /etc/steadybit/extension-jvm and then restart the service.

Extension registration

Make sure that the extension is registered with the agent. In most cases this is done automatically. Please refer to the documentation for more information about extension registration and how to verify.

Anatomy of the extension / Security

We try to limit the needed access needed for the extension to the absolute minimum. So the extension itself can run as a non-root user on a read-only root file-system and will by default if deployed using the provided helm-chart. In order do execute certain actions the extension needs certain capabilities.

discovery / state attacks

For discovery the extension needs access to the container runtime socket.

resource and network attacks

The jvm attachment reuses the target container's linux namespace(s), control group(s) and user. This requires the following capabilities: SYS_ADMIN, SYS_RESOURCE, SYS_PTRACE, KILL, NET_ADMIN, DAC_OVERRIDE, SETUID, SETGID, AUDIT_WRITE.

FAQ

How do I exclude my JVM from the discovery mechanism?

Add the steadybit.agent.disable-jvm-attachment flag to your JVM commandline like in this example:

java -Dsteadybit.agent.disable-jvm-attachment -jar spring-boot-sample.jar --server.port=0

The Spring discovery is not showing my application name

The extension uses the spring.application.name property to determine the application name. The extension will try to lookup the property by the JMX Environment.

If JMX is not enabled or the values are sanitized by Spring Boot, the extension will try to instrument the application context and get the value from there. This might not work in an unused application, as the instrumentation needs some events to discover the application context.

Workarounds:

• Calling any HTTP endpoint is sufficient to trigger the application context instrumentation.
• Provide a SanitizingFunction and exclude the spring.application.name from sanitization.
• Set management.endpoint.env.show-values to always to expose the environment values. (Be careful, this will disable springs default sanitization!)