要在线上查看gc情况，进入k8s容器的bash，ps -ef 发现目标的java线程的进程号是1，运行jmap 报错：

Unable to get pid of LinuxThreads manage thread

查询了一下，原来是1是默认的启动进程，Dockerfile的ENTRYPOINT的执行默认就是 1。

优雅解法
https://zhuanlan.zhihu.com/p/59796137
https://cloud.tencent.com/developer/article/1838250

修改Dcokerfile java启动方式

FROM openjdk:8-jdk-alpine
VOLUME /tmp
ENV TZ=Asia/Shanghai
RUN apk add --no-cache tini
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
ADD target/diversion-0.0.1-SNAPSHOT.jar diversion-0.0.1-SNAPSHOT.jar
ENTRYPOINT ["tini","java","-Djava.security.egd=file:/dev/./urandom","-jar","/xxxx-0.0.1-SNAPSHOT.jar"]

构建并上传镜像到镜像仓库

docker build -t ccr.ccs.tencentyun.com/xxxx/xxxx:xxxx
docker push ccr.ccs.tencentyun.com/xxxx/xxxx:xxxx

部署应用并测试

cat > test.yaml << EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: test
spec:
  replicas: 1
  strategy:
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  selector:
    matchLabels:
      app: test
  template:
    metadata:
      labels:
        app: test
    spec:
      containers:
        - name: test
          image: ccr.ccs.tencentyun.com/xxxx/xxxx:xxxx
          env:
          - name: SPRING_PROFILES_ACTIVE
            value: "official"
          ports:
            - containerPort: test
          resources:
            requests:
              memory: "256M"
              cpu: "250m"
            limits:
              memory: "1024M"
              cpu: "500m" 
      imagePullSecrets:                                              
        - name: tencent
---

apiVersion: v1
kind: Service
metadata:
  name: test
  labels:
    app: test
spec:
  ports:
  - port: 8081
    protocol: TCP
    targetPort: 8081
  selector:
    app: test
EOF

kubectl apply -f test.yaml -n test
kubectl exec -it xxxxxxx sh -n test
top

几番查找。幡然醒悟，只要不要让那个java进程直接启动就好了。

修改Dockerfile

RUN echo "java -jar xxx.jar" > /run.sh && chmod 777 /run.sh

ENTRYPOINT ["/bin/sh","/run.sh"]

之后进入容器，ps -ef ，之前的java进程变成了6。