springboot-dd-tracer

Spring Boot 3.5.9 — Datadog APM Instrumentation

Instrument a Spring Boot 3.5.9 REST API with Datadog APM on Kubernetes using manual init container injection for the Datadog Java tracer (dd-java-agent.jar).

Prerequisites

• Skill setup-springboot has been completed successfully (app built and deployed to Kubernetes)
• A Kubernetes cluster with the Datadog Agent deployed (see aws-ec2 or gcp-gke plugins)
• kubectl configured to access the cluster
• Datadog API key configured in the cluster

Instructions

1. Datadog APM via init container injection

The k8s/deployment.yaml already includes the Datadog tracer setup:

• Init container copies dd-java-agent.jar from gcr.io/datadoghq/dd-lib-java-init:latest
• Environment variables set JAVA_TOOL_OPTIONS=-javaagent:/datadog-lib/dd-java-agent.jar plus DD_SERVICE, DD_ENV, DD_AGENT_HOST, DD_PROFILING_ENABLED, DD_LOGS_INJECTION, DD_TRACE_SAMPLE_RATE, DD_RUNTIME_METRICS_ENABLED
• Shared volume (emptyDir) mounts in both init and app containers

This approach is preferred over the Datadog admission controller webhook, which excludes its own namespace from auto-injection.

2. Generate traffic

kubectl port-forward svc/springboot3dot5dot9-sandbox 8080:80 &
for i in $(seq 1 60); do
  curl -s http://localhost:8080/api/data > /dev/null
  curl -s -X POST http://localhost:8080/api/submit -H "Content-Type: application/json" -d "{\"key\":\"test\",\"iteration\":$i}" > /dev/null
  curl -s -X PUT http://localhost:8080/api/update > /dev/null
  sleep 2
done

Validation

# Verify init container exists
kubectl get pods -l app=springboot3dot5dot9-sandbox \
  -o jsonpath='{.items[0].spec.initContainers[*].name}'
# Expected: datadog-lib-java-init

# Check tracer initialization
kubectl logs -l app=springboot3dot5dot9-sandbox --tail=30 | grep "DATADOG TRACER CONFIGURATION"

# Verify traces received by agent
kubectl exec $(kubectl get pods -l app.kubernetes.io/component=agent -o name | head -1) \
  -c agent -- agent status 2>/dev/null | grep -A 10 "Receiver (previous minute)"

In the Datadog UI:

• APM > Services — look for springboot3dot5dot9-sandbox with env:sandbox
• APM > Traces — filter by service:springboot3dot5dot9-sandbox
• APM > Services > Runtime Metrics — JVM heap, GC, threads

Troubleshooting

No traces appearing in Datadog

Cause: The DD_AGENT_HOST points to a service that doesn't exist, or the Datadog Agent DaemonSet is not running. Fix: Verify the agent is running: kubectl get pods -l app.kubernetes.io/component=agent. Check DD_AGENT_HOST value matches the agent service FQDN.

DATADOG TRACER CONFIGURATION not in logs

Cause: The init container failed to copy dd-java-agent.jar, or JAVA_TOOL_OPTIONS is not set. Fix: Check init container logs: kubectl logs <POD> -c datadog-lib-java-init. Verify the shared volume is mounted correctly.

Runtime metrics not appearing

Cause: DogStatsD port 8125 not exposed on the agent service. Fix: Verify the datadog-agent service exposes port 8125/UDP. The agent DaemonSet should have DD_DOGSTATSD_NON_LOCAL_TRAFFIC=true.

Traces show env:none instead of env:sandbox

Cause: DD_ENV environment variable not set on the application pods. Fix: Verify DD_ENV=sandbox is in the deployment manifest and reapply.