要动态更新容器里某些进程的配置，例如nginx。所以需要实时获取配置更新，并同步到容器里的配置文件里，采用的方法是用confd从etcd采集数据，然后更新配置文件的方法。
现有的方案是把confd+nginx放在同一个容器里，虽然能解决问题，但是不够优雅，毕竟一个容器只跑一个进程好。
恰好业务是跑在k8s上，k8s关于pod的文档上说

Containers within a pod share an IP address and port space, and can find each other via localhost. They can also communicate with each other using standard inter-process communications like SystemV semaphores or POSIX shared memory. Containers in different pods have distinct IP addresses and can not communicate by IPC

如果同一个pod里的进程，可以互相看到对方，那么就可以不用修改，直接把现有一个容器拆成两个容器了。

提前剧透一下结论，是看不到的。因为

The context of the pod can be defined as the conjunction of several Linux namespaces:

PID namespace (applications within the pod can see each other’s processes)

network namespace (applications within the pod have access to the same IP and port space)

IPC namespace (applications within the pod can use SystemV IPC or POSIX message queues to communicate)

UTS namespace (applications within the pod share a hostname)

In terms of Docker constructs, a pod consists of a colocated group of Docker containers with shared volumes. PID namespace sharing is not yet implemented with Docker.

创建pod

创建两个容器的pod

apiVersion: v1
kind: Pod
metadata:
  name: ipc2
  labels:
    app: web
spec:
  containers:
    - name: registry
      image: registry
      ports:
        - containerPort: 5000
    - name: nginx
      image: nginx:1.9
      ports:
        - containerPort: 80

进入其中一个ps和netstat

./kubectl exec -it ipc2 bash

# 看进程
ps aux
# 结果，只能看到registry的进程
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.4  53228 15992 ?        Ss   14:56   0:00 /usr/bin/python
root        13  1.0  1.0 110492 39600 ?        S    14:56   0:03 /usr/bin/python
root        14  1.0  0.9 110256 38804 ?        S    14:56   0:03 /usr/bin/python
root        17  0.9  0.9 110272 38820 ?        S    14:56   0:03 /usr/bin/python
root        18  1.0  0.9 110276 38816 ?        S    14:56   0:03 /usr/bin/python
root        44  0.0  0.0  18148  3364 ?        Ss+  15:00   0:00 bash
root        60  2.0  0.0  18152  3192 ?        Ss   15:01   0:00 bash
root        74  0.0  0.0  15572  2164 ?        R+   15:01   0:00 ps aux

# 看端口
root@ipc2:/# netstat -anplt
# 结果，网络共享了
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:5000            0.0.0.0:*               LISTEN      -
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      -

进入另一个容器

进入nginx容器看看进程

docker exec -it k8s_nginx.fb0f31c6_ipc2_default_82fd2fb7-42c0-11e6-a4f1-d43d7e2c2527_c689aa68 bash
root@ipc2:/# ps axu

# 只能看到nginx的进程
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.1  31684  5100 ?        Ss   14:57   0:00 nginx: master process nginx -g daemon off;
nginx        5  0.0  0.0  32068  2904 ?        S    14:57   0:00 nginx: worker process
root         6  0.0  0.0  20224  3272 ?        Ss   15:00   0:00 bash
root        19  0.0  0.0  17500  2096 ?        R+   15:09   0:00 ps axu

结论

网络、UTC、IPC都共享，但是PID不能共享。

本博客欢迎转发,但请保留原作者信息
github:codejuan
博客地址:http://blog.decbug.com/

Continuous Learning

kubernetes:pod内IPC

创建pod

进入其中一个ps和netstat

进入另一个容器

结论