Using datakit-operator to Inject dd-java-agent¶

Introduction¶

In a Kubernetes environment, when integrating Java applications with APM, the dd-java-agent.jar package needs to be used. To avoid modifying the application's image, a common approach is to use initContainers in the deployment YAML of the application, leveraging the shared storage among containers within the same Pod to utilize dd-java-agent.jar. This method results in identical initContainers sections appearing in each deployment file.

Is it possible to extract these identical sections to reduce workload? The answer is yes, which involves using an open-source Admission Controller (Admission Controller) from Guance. datakit-operator provides the functionality to inject dd-lib files and environment variables into specific Pods, currently supporting Java, Python, and JavaScript.

Prerequisites¶

• You need to first create a Guance account.
• A Kubernetes cluster.
• DataKit has been deployed using DaemonSet, and ddtrace collector has been enabled.

Steps¶

1 Deploy datakit-operator¶

Download datakit-operator.yaml and deploy it to your Kubernetes cluster.

wget https://static.guance.com/datakit-operator/datakit-operator.yaml
kubectl apply -f datakit-operator.yaml

2 Deploy Application¶

2.1 Write Dockerfile¶

Write the Dockerfile for your application, primarily exposing JAVA_OPTS to facilitate the injection of the javaagent package externally.

FROM openjdk:8u292

RUN /bin/cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime
RUN echo 'Asia/Shanghai' >/etc/timezone

ENV jar service-demo-1.0-SNAPSHOT.jar

ENV workdir /data/app/
RUN mkdir -p ${workdir}
COPY ${jar} ${workdir}
WORKDIR ${workdir}
ENTRYPOINT ["sh", "-ec", "exec java ${JAVA_OPTS} -jar ${jar} ${PARAMS} "]

After writing, push the image to the repository. Below, we directly pull the image using 172.16.0.246/df-demo/service-log-demo:v1.

2.2 Modify Application YAML¶

Add annotations to the application's YAML.

      annotations:
        admission.datakit/java-lib.version: ""

2.3 Modify Application YAML¶

Declare the JAVA_OPTS environment variable. The application can now access the automatically injected /datadog-lib/dd-java-agent.jar package. For startup parameters, refer to javaagent options. Here, the service name is set to java-demo-service.

        - name: JAVA_OPTS
          value: |-
            -javaagent:/datadog-lib/dd-java-agent.jar -Ddd.service.name=java-demo-service -Ddd.tags=container_host:$(POD_NAME) -Ddd.env=dev -Ddd.agent.port=9529

apiVersion: v1
apiVersion: apps/v1
kind: Deployment
metadata:
  name: guance-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: guance-pod
  template:
    metadata:
      labels:
        app: guance-pod
      annotations:
        admission.datakit/java-lib.version: ""
    spec:
      containers:
      - name: guance-demo-container
        image: 172.16.0.246/df-demo/service-log-demo:v1
        env:
        - name: HOST_IP
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: status.hostIP
        - name: HOST_NAME
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: spec.nodeName
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        #- name: DD_AGENT_HOST
        #  valueFrom:
        #    fieldRef:
        #      apiVersion: v1
        #      fieldPath: status.hostIP
        - name: JAVA_OPTS
          value: |-
            -javaagent:/datadog-lib/dd-java-agent.jar -Ddd.service.name=java-demo-service -Ddd.tags=container_host:$(POD_NAME) -Ddd.env=dev -Ddd.agent.port=9529
        ports:
        - containerPort: 8090
          protocol: TCP
        volumeMounts:
        - mountPath: /data/app/logs
          name: varlog
      restartPolicy: Always
      volumes:
      - name: varlog
        emptyDir: {}

2.4 Deploy Application¶

kubectl apply -f java-demo.yaml

3 Trace Reporting¶

Obtain the IP address of the Pod, access the application's interface to generate trace data.

Log in to Guance - [APM], based on the server java-demo-service, you can query the traces.