JavaAgent Introduction

To see the final injected agent’s configuration, we define a CustomDefinitionResource called JavaAgent.

When the pod is injected, the pod will be labeled with sidecar.skywalking.apache.org/succeed, then the controller will watch the specific pod labeled with sidecar.skywalking.apache.org/succeed. After the pod is created, the controller will create JavaAgent(custom resource), which contains the final agent configuration as below.

Spec

Field Name	Description
podSelector	We hope users can use workloads to create pods, the podSelector is the selector label of workload.
serviceName	serviceName is an important attribute that needs to be printed.
backendService	backendService is an important attribute that needs to be printed.
agentConfiguration	agentConfiguration contains serviceName、backendService and covered agent configuration, other default configurations will not be displayed, please see agent.config for details.

Status

Field Name	Description
creationTime	The creation time of the JavaAgent
lastUpdateTime	The last Update time of the JavaAgent
expectedInjectiedNum	The number of the pod that need to be injected
realInjectedNum	The real number of injected pods.

Demo

This demo shows the usage of javaagent. If you want to see the complete process, please see java-agent-injector-usagefor details.

When we use java-agent-injector, we can get custom resources as below.

$ kubectl get javaagent -A
NAMESPACE   NAME                  PODSELECTOR   SERVICENAME            BACKENDSERVICE
default     app-demo1-javaagent   app=demo1     Your_ApplicationName   127.0.0.1:11800
default     app-demo2-javaagent   app=demo2     Your_ApplicationName   127.0.0.1:11800
$ kubectl get pod -l app=demo1
NAME                    READY   STATUS    RESTARTS   AGE
demo1-bb97b8b4d-bkwm4   1/1     Running   0          28s
demo1-bb97b8b4d-wxgs2   1/1     Running   0          28s
$ kubectl get pod -l app=demo2
NAME     READY   STATUS    RESTARTS   AGE
app2-0   1/1     Running   0          27s
app2-1   1/1     Running   0          25s
app2-2   1/1     Running   0          23s

If we want to see more information, we can get the specific javaagent’s yaml as below.

$ kubectl get javaagent app-demo1-javaagent -oyaml
apiVersion: operator.skywalking.apache.org/v1alpha1
kind: JavaAgent
metadata:
  creationTimestamp: "2021-10-14T07:07:12Z"
  generation: 1
  name: app-demo1-javaagent
  namespace: default
  ownerReferences:
  - apiVersion: apps/v1
    blockOwnerDeletion: true
    controller: true
    kind: ReplicaSet
    name: demo1-bb97b8b4d
    uid: c712924f-4652-4c07-8332-b3938ad72392
  resourceVersion: "330808"
  selfLink: /apis/operator.skywalking.apache.org/v1alpha1/namespaces/default/javaagents/app-demo1-javaagent
  uid: 9350338f-15a5-4832-84d1-530f8d0e1c3b
spec:
  agentConfiguration:
    agent.namespace: default-namespace
    agent.service_name: Your_ApplicationName
    collector.backend_service: 127.0.0.1:11800
  backendService: 127.0.0.1:11800
  podSelector: app=demo1
  serviceName: Your_ApplicationName
status:
  creationTime: "2021-10-14T07:07:12Z"
  expectedInjectiedNum: 2
  lastUpdateTime: "2021-10-14T07:07:14Z"
  realInjectedNum: 2