Welcome back to our series of hands-on introductions to using Cryostat 2.0. This article shows you how to preconfigure custom event templates for Java application monitoring with JDK Flight Recorder (JFR). First, you'll use the new Cryostat Operator and a Red Hat OpenShift
ConfigMap to create a custom event template, then you'll instruct the Cryostat Operator to use the
ConfigMap when deploying Cryostat. You can use the OpenShift console to interact with Cryostat or edit the YAML file for your Cryostat custom resource. We'll demonstrate both approaches.
Note: Cryostat is JDK Flight Recorder for Kubernetes or Red Hat OpenShift. The Red Hat build of Cryostat 2.0 is now widely available in technology preview. Cryostat 2.0 introduces many new features and improvements, such as automated rules, a better API response JSON format, custom targets, concurrent target JMX connections, WebSocket push notifications, and more. The Red Hat build includes the Cryostat Operator to simplify and automate Cryostat deployment on OpenShift.
Create a custom template and ConfigMap
With Cryostat, you can download existing template files directly from a Java virtual machine (JVM). Once you've downloaded a template file to your local machine, you can use the JDK Mission Control (JMC) Template Manager to easily edit the template to suit your needs.
After customizing the template file, it's fairly simple to create a
ConfigMap from it. This
ConfigMap stores the template file inside of the cluster where Cryostat will run. You can use
kubectl in the namespace where Cryostat is to be deployed. Here's the source if you use the former:
$ oc create configmap my-template --from-file=/path/to/custom.jfc
This command creates a
my-template from a file on your local machine, located at
/path/to/custom.jfc. The file will be placed inside the
ConfigMap under the
Add your ConfigMap to the Cryostat Operator
Once you've created a
ConfigMap, you only need to instruct the Cryostat Operator to use it when deploying Cryostat. You can do this when you create a Cryostat custom resource, or by updating an existing one. If you're installing Cryostat using the OpenShift console, select Event Templates under the Cryostat custom resource that you want to update. Choose Add Event Template. The Config Map Name drop-down list will display all
ConfigMaps in the local namespace. Select the
ConfigMap containing the event template you just created. For Filename, enter the name of the
.jfc file within the
ConfigMap. In Figure 1, we're using
custom.jfc, which we created in the previous section.
You can also work directly with the YAML for the Cryostat custom resource. The process is similar to what you did in the console. Add an
eventTemplates property to the
spec section, if one isn't already present. Then, add an array entry with
configMapName referencing the name of the
ConfigMap, and a
filename referencing the filename within the
ConfigMap. The YAML below mirrors what we did in the OpenShift console example in Figure 1.
apiVersion: operator.cryostat.io/v1beta1 kind: Cryostat metadata: name: cryostat-sample spec: eventTemplates: - configMapName: custom-template filename: my-template.jfc
Once you've saved your changes to the Cryostat custom resource, the Cryostat Operator will deploy Cryostat with this template preconfigured. Visiting the Cryostat web application will show that the template is present and available to use for creating new JDK flight recordings, as you can see in Figure 2.
In this article, you've learned how to preconfigure Cryostat with customized event templates using OpenShift
ConfigMaps. You can use customized templates to gather the specific data you need in your JDK flight recordings. Visit Cryostat.io and see the other articles in this series for further details: