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Docker

Docker is a container-based virtualization platform. When you run Java applications in a Docker container, you can adjust the application's performance and resource usage by adding JVM options. This document explains how to modify the Dockerfile to add JVM options.

Note

The Docker must have been installed and the Docker images must be built for Java applications.

Applying the agent​

Based on an existing Docker image, build an image with the WhaTap agent settings added.

Note

This document covers only the installation of the Java agent. To apply with WhaTap Kubernetes monitoring, see the following.

Creating the Docker build directory​

Create a Docker build directory.

mkdir -p {Docker build dir}

Creating the agent configuration file​

Create the whatap.conf file.

cat >{Docker build Dir}/whatap.conf <<EOL
#Enter the access key.
license=XXXXXXXXXXXXXX-XXXXXXXXXXXXXX-XXXXXXXXXXXXXX 
#Enter the collection server IP.
whatap.server.host=xx.xx.xx.xx/yy.yy.yy.yy 
EOL

Creating the Dockerfile​

To build an image, you can copy the jar files from the WhaTap image to the -javaagent option.

cat >/home/silver/whatap/docker/Dockerfile <<EOL
FROM whatap/kube_mon as build
## Create an actual image (Add the WhaTap image)
## $Image_Name (image name)
FROM $Image_Name
RUN mkdir -p /whatap
COPY --from=build /data/agent/micro/whatap.agent-*.jar /whatap
COPY ./whatap.conf /whatap/
#...
EOL

Applying JAVA_OPTS​

Add the following to JAVA_OPT:

WHATAP_HOME=/whatap
WHATAP_JAR=ls ${WHATAP_HOME}/whatap.agent-*.jar | sort -V | tail -1
export JAVA_OPTS="-javaagent:${WHATAP_JAR} "

Building the Docker​

Build the Docker.

cd docker
docker build -t $Image_Name
Note

In case of Java 17 or later, add the following options for reflection.


--add-opens=java.base/java.lang=ALL-UNNAMED

Note

You can modify the Java agent file name by using the Rename function. Once the Java agent name has been modified, enter a new name in JAVA_OPTS.

Example of how to modify the Java agent name

java -cp whatap.agent-X.Y.Z.jar whatap.agent.setup.Rename -from whatap.agent-X.Y.Z.jar -to whatap.agent.jar

Viewing the heap histogram​

WhaTap's Java Monitoring provides the function to view the status of heap occupancy objects in the JVM memory (sizes for each object in heap memory). In APP > Instance performance analysis, select the Heap histogram tab.

Java versions 6 to 8 support basic functions without the JVM options. However, for some Java versions, the JVM options must be applied as follows:

  • Java 9 to Java 15

    -Djdk.attach.allowAttachSelf=true
    example
    java -javaagent:{WHATAP_HOME}/whatap.agent-X.Y.Z.jar -Djdk.attach.allowAttachSelf=true -jar {application.jar}

  • Java 16 or later

    -Djdk.attach.allowAttachSelf=true
    --add-opens=jdk.attach/sun.tools.attach=ALL-UNNAMED
    example
    java -javaagent:{WHATAP_HOME}/whatap.agent-X.Y.Z.jar -Djdk.attach.allowAttachSelf=true --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=jdk.attach/sun.tools.attach=ALL-UNNAMED -jar {application.jar}
Note

It does not support Java 5 or earlier and IBM Java.

Next steps​

  • Open source tracing

    Depending on the framework or open source library used in applications, you may need to add agent options. For example, when using spring-boot-3.x, feign-client-11, or okhttp3-4.4 with a framework or open source, set the options as follows:

    whatap.conf
    weaving=spring-boot-3.0,feign-11,okhttp3-4.4

    For information on how to configure the framework or open source library that suits your application environment, see the following.

  • Checking the installation

    If you have created a project, installed an agent, and applied all JVM options, see the checklist in the following.

  • Installation troubleshooting

    It provides various problems that may occur when installing the agent and specific instructions for resolving them. It provides solutions against various situations, including firewall configuration, SpringBoot and Tomcat JMX configuration, and server configuration using the OSGI framework. For more information, see the following.

  • Agent setting

    It provides various features for monitoring by applying some options to the agent configuration file (whatap.conf). It includes basic configuration, configuration for server connection and data transfer, how to manage the configuration files for multiple application servers, and transaction tracing, and more. For more information, see the following.

  • Starting the monitoring

    After all settings are made, restart the application server. The agent starts collecting data. First, check whether the monitoring data has been collected in Application Dashboard. For more information about Application Dashboard, see the following.