Use datakit-operator to inject dd-java-agent¶

Introduction¶

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

So, can these identical parts be extracted to further reduce the workload? The answer is yes, and this is where Guance's open-source Admission Controller (Admission Controllers) comes into play. datakit-operator provides the function of injecting dd-lib files and environments into special Pods, currently supporting java, python, and js.

Prerequisites¶

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

Procedure¶

1 Deploy datakit-operator¶

Download datakit-operator.yaml and deploy it to the 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, mainly exposing JAVA_OPTS so that the javaagent package can be injected 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 annotation to the application's yaml.

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

2.3 Modify Application yaml¶

Declare the JAVA_OPTS environment variable. The application already has access to the automatically injected /datadog-lib/dd-java-agent.jar package. Startup parameters can refer to javaagent Parameters. 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 Report on the Trace¶

Get the pod's IP and 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 trace.