13.1、NG容器热更新

Nginx作为WEB服务器被广泛使用。其自身支持热更新，在修改配置文件后，使用nginx -s reload命令可以不停服务重新加载配置。然而对于Dockerize的Nginx来说，如果每次都进到容器里执行对应命令去实现配置重载，这个过程是很痛苦的。本文介绍了一种kubernetes集群下nginx的热更新方案。

首先我们创建正常的一个nginx资源，资源清单如下：

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-config
data:
  default.conf: |-
      server {
        server_name localhost;
        listen 80 default_server;
        location = /healthz {
          add_header Content-Type text/plain;
          return 200 'ok';
        }
        location / {
            root   /usr/share/nginx/html;
            index  index.html index.htm;
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   /usr/share/nginx/html;
        }
      }
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app
        image: nginx
        imagePullPolicy: IfNotPresent
        volumeMounts:
        - name: nginx-config
          mountPath: /etc/nginx/conf.d
      volumes:
      - name: nginx-config
        configMap:
         name: nginx-config

然后创建资源对象。

# kubectl get pod -o wide
NAME                     READY   STATUS    RESTARTS   AGE    IP               NODE         NOMINATED NODE   READINESS GATES
my-app-9bdd6cbbc-x9gnt   1/1     Running   0          112s   192.168.58.197   k8s-node02   <none>           <none>

然后我们访问pod资源，如下：

# curl -I 192.168.58.197
HTTP/1.1 200 OK
Server: nginx/1.17.10
Date: Tue, 26 May 2020 06:18:18 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 14 Apr 2020 14:19:26 GMT
Connection: keep-alive
ETag: "5e95c66e-264"
Accept-Ranges: bytes

现在我们来更新一下ConfigMap，也就是更改配置文件如下：

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-config
data:
  default.conf: |-
      server {
        server_name localhost;
        listen 8080 default_server;
        location = /healthz {
          add_header Content-Type text/plain;
          return 200 'ok';
        }
        location / {
            root   /usr/share/nginx/html;
            index  index.html index.htm;
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   /usr/share/nginx/html;
        }
      }

等待数秒…..
然后我们可以看到nginx pod里的配置信息已经更改为如下：

# kubectl exec -it my-app-9bdd6cbbc-x9gnt -- /bin/bash
root@my-app-9bdd6cbbc-x9gnt:/# cat  /etc/nginx/conf.d/default.conf 
server {
  server_name localhost;
  listen 8080 default_server;
  location = /healthz {
    add_header Content-Type text/plain;
    return 200 'ok';
  }
  location / {
      root   /usr/share/nginx/html;
      index  index.html index.htm;
  }
  error_page   500 502 503 504  /50x.html;
  location = /50x.html {
      root   /usr/share/nginx/html;
  }
}
root@my-app-9bdd6cbbc-x9gnt:/#

这时候我们访问8080是不通的，访问80是没问题的，如下：

[root@k8s-master nginx]# curl -I 192.168.58.197
HTTP/1.1 200 OK
Server: nginx/1.17.10
Date: Tue, 26 May 2020 06:21:05 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 14 Apr 2020 14:19:26 GMT
Connection: keep-alive
ETag: "5e95c66e-264"
Accept-Ranges: bytes
[root@k8s-master nginx]# curl -I 192.168.58.197:8080
curl: (7) Failed connect to 192.168.58.197:8080; Connection refused

我们可以看到，我们需要的配置文件已经更新的，但是并没有使用上，pod里的nginx也没有重载配置文件，这时候如果我们重新部署Pod，资源对象肯定就生效了。
但是这并不我们想要的效果，我们希望配置文件更改了，服务也跟着reload，并不需要我们手动的去干预。
目前有三种方法：

• 应用本身可以检测配置文件，然后自动reload
• 给Pod增加一个sidecar，用它来检测配置文件
• 第三方组件reloader，在deployment的annotations增加字段reloader.stakater.com/auto: "true",即可检测configmap的更改来重启pod

应用本身检测的话这里就不做介绍了。这里主要来实验一下第2，3种方法

一、以sidecar形式

1.1、方法

• Kubernetes集群中部署Nginx Pod。该Pod包含两个Container，一个是nginx container，实现nginx自身的功能；另一个是nginx-reloader container，负责实时监测目标configmap的变化，当发现configmap更新以后，会主动向nginx的master进程发送HUP信号，实现配置的热加载。
• 配置文件是通过ConfigMap的形式挂载到Nginx Pod上，两个Container共享该ConfigMap。
• 依赖K8s集群的shareProcessNamespace特性（版本需在1.12之后），两个Container需要在Pod中共享进程名字空间。

  1.2、实现

  1.2.1、镜像制作

  （1）、主容器使用官方NG容器即可
  （2）、sidecar容器制作

Dockerfile如下：

FROM golang:1.12.0 as build
RUN go get github.com/fsnotify/fsnotify
RUN go get github.com/shirou/gopsutil/process
RUN mkdir -p /go/src/app
ADD main.go /go/src/app/
WORKDIR /go/src/app
RUN CGO_ENABLED=0 GOOS=linux go build -a -o nginx-reloader .
# main image
FROM nginx:1.14.2-alpine
COPY --from=build /go/src/app/nginx-reloader /
CMD ["/nginx-reloader"]

main.go脚本如下：

package main
import (
    "log"
    "os"
    "path/filepath"
    "syscall"
    "github.com/fsnotify/fsnotify"
    proc "github.com/shirou/gopsutil/process"
)
const (
    nginxProcessName = "nginx"
    defaultNginxConfPath = "/etc/nginx"
    watchPathEnvVarName = "WATCH_NGINX_CONF_PATH"
)
var stderrLogger = log.New(os.Stderr, "error: ", log.Lshortfile)
var stdoutLogger = log.New(os.Stdout, "", log.Lshortfile)
func getMasterNginxPid() (int, error) {
    processes, processesErr := proc.Processes()
    if processesErr != nil {
        return 0, processesErr
    }
    nginxProcesses := map[int32]int32{}
    for _, process := range processes {
        processName, processNameErr := process.Name()
        if processNameErr != nil {
            return 0, processNameErr
        }
        if processName == nginxProcessName {
            ppid, ppidErr := process.Ppid()
            if ppidErr != nil {
                return 0, ppidErr
            }
            nginxProcesses[process.Pid] = ppid
        }
    }
    var masterNginxPid int32
    for pid, ppid := range nginxProcesses {
        if ppid == 0 {
            masterNginxPid = pid
            break
        }
    }
    stdoutLogger.Println("found master nginx pid:", masterNginxPid)
    return int(masterNginxPid), nil
}
func signalNginxReload(pid int) error {
    stdoutLogger.Printf("signaling master nginx process (pid: %d) -> SIGHUP\n", pid)
    nginxProcess, nginxProcessErr := os.FindProcess(pid)
    if nginxProcessErr != nil {
        return nginxProcessErr
    }
    return nginxProcess.Signal(syscall.SIGHUP)
}
func main() {
    watcher, watcherErr := fsnotify.NewWatcher()
    if watcherErr != nil {
        stderrLogger.Fatal(watcherErr)
    }
    defer watcher.Close()
    done := make(chan bool)
    go func() {
        for {
            select {
            case event, ok := <-watcher.Events:
                if !ok {
                    return
                }
                if event.Op&fsnotify.Create == fsnotify.Create {
                    if filepath.Base(event.Name) == "..data" {
                        stdoutLogger.Println("config map updated")
                        nginxPid, nginxPidErr := getMasterNginxPid()
                        if nginxPidErr != nil {
                            stderrLogger.Printf("getting master nginx pid failed: %s", nginxPidErr.Error())
                            continue
                        }
                        if err := signalNginxReload(nginxPid); err != nil {
                            stderrLogger.Printf("signaling master nginx process failed: %s", err)
                        }
                    }
                }
            case err, ok := <-watcher.Errors:
                if !ok {
                    return
                }
                stderrLogger.Printf("received watcher.Error: %s", err)
            }
        }
    }()
    pathToWatch, ok := os.LookupEnv(watchPathEnvVarName)
    if !ok {
        pathToWatch = defaultNginxConfPath
    }
    stdoutLogger.Printf("adding path: `%s` to watch\n", pathToWatch)
    if err := watcher.Add(pathToWatch); err != nil {
        stderrLogger.Fatal(err)
    }
    <-done
}

1.2.2、部署NG

（1）、NG的配置以configMap进行部署：
nginx-config.yaml

// nginx-config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-config
data:
  default.conf: |-
      server {
        server_name localhost;
        listen 80 default_server;
        location = /healthz {
          add_header Content-Type text/plain;
          return 200 'ok';
        }
        location / {
            root   /usr/share/nginx/html;
            index  index.html index.htm;
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   /usr/share/nginx/html;
        }
      }

（2）、NG的Deployment清单(需打开共享进程命名空间特性：shareProcessNamespace: true)：
nginx-deploy.yaml

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      name: nginx
      labels:
        app: nginx
    spec:
      shareProcessNamespace: true
      containers:
        - name: nginx
          image: nginx
          imagePullPolicy: IfNotPresent
          volumeMounts:
            - name: nginx-config
              mountPath: /etc/nginx/conf.d
              readOnly: true           
        - name: nginx-reloader
          image: registry.cn-hangzhou.aliyuncs.com/rookieops/nginx-reloader:v1
          imagePullPolicy: IfNotPresent
          env:
            - name: WATCH_NGINX_CONF_PATH
              value: /etc/nginx/conf.d
          volumeMounts:
          - name: nginx-config
            mountPath: /etc/nginx/conf.d
            readOnly: true
      volumes:
      - name: nginx-config
        configMap:
          name: nginx-config

手动修改configmap后，reloader监测到configmap变化，会主动向nginx主进程发起HUP信号，实现配置热更新。

二、第三方插件reloader

项目地址：https://github.com/stakater/Reloader
资源清单如下，我修改了镜像地址：

---
# Source: reloader/templates/clusterrole.yaml
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  labels:
    app: reloader-reloader
    chart: "reloader-v0.0.58"
    release: "reloader"
    heritage: "Tiller"
  name: reloader-reloader-role
  namespace: default
rules:
  - apiGroups:
      - ""
    resources:
      - secrets
      - configmaps
    verbs:
      - list
      - get
      - watch
  - apiGroups:
      - "apps"
    resources:
      - deployments
      - daemonsets
      - statefulsets
    verbs:
      - list
      - get
      - update
      - patch
  - apiGroups:
      - "extensions"
    resources:
      - deployments
      - daemonsets
    verbs:
      - list
      - get
      - update
      - patch
---
# Source: reloader/templates/clusterrolebinding.yaml
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  labels:
    app: reloader-reloader
    chart: "reloader-v0.0.58"
    release: "reloader"
    heritage: "Tiller"
  name: reloader-reloader-role-binding
  namespace: default
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: reloader-reloader-role
subjects:
  - kind: ServiceAccount
    name: reloader-reloader
    namespace: default
---
# Source: reloader/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: reloader-reloader
    chart: "reloader-v0.0.58"
    release: "reloader"
    heritage: "Tiller"
    group: com.stakater.platform
    provider: stakater
    version: v0.0.58
  name: reloader-reloader
spec:
  replicas: 1
  revisionHistoryLimit: 2
  selector:
    matchLabels:
      app: reloader-reloader
      release: "reloader"
  template:
    metadata:
      labels:
        app: reloader-reloader
        chart: "reloader-v0.0.58"
        release: "reloader"
        heritage: "Tiller"
        group: com.stakater.platform
        provider: stakater
        version: v0.0.58
    spec:
      containers:
      - env:
        image: "registry.cn-hangzhou.aliyuncs.com/rookieops/stakater-reloader:v0.0.58"
        imagePullPolicy: IfNotPresent
        name: reloader-reloader
        args:
      serviceAccountName: reloader-reloader
---
# Source: reloader/templates/role.yaml
---
# Source: reloader/templates/rolebinding.yaml
---
# Source: reloader/templates/service.yaml
---
# Source: reloader/templates/serviceaccount.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  labels:
    app: reloader-reloader
    chart: "reloader-v0.0.58"
    release: "reloader"
    heritage: "Tiller"
  name: reloader-reloader

然后部署资源，结果如下：

 kubectl get pod
NAME                               READY   STATUS    RESTARTS   AGE
my-app-9bdd6cbbc-x9gnt             1/1     Running   0          38m
reloader-reloader-ff767bb8-cpzgz   1/1     Running   0          56s

然后给deployment增加一个annotations。如下：

kubectl patch deployments.apps my-app -p '{"metadata": {"annotations": {"reloader.stakater.com/auto": "true"}}}'

然后我们更改configMap清单，重新apply过后，我们可以看到pod会删除重启，如下：

 kubectl get pod -o wide
NAME                               READY   STATUS        RESTARTS   AGE     IP               NODE         NOMINATED NODE   READINESS GATES
my-app-7c4fc77f5f-w4mbn            1/1     Running       0          3s      192.168.58.202   k8s-node02   <none>           <none>
my-app-df6fbdb67-bnftb             1/1     Terminating   0          35s     192.168.58.201   k8s-node02   <none>           <none>
reloader-reloader-ff767bb8-cpzgz   1/1     Running       0          3m47s   192.168.85.195   k8s-node01   <none>           <none>

然后我们curl pod也可以通了，如下：

# curl 192.168.58.202:8080 -I
HTTP/1.1 200 OK
Server: nginx/1.17.10
Date: Tue, 26 May 2020 06:58:38 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 14 Apr 2020 14:19:26 GMT
Connection: keep-alive
ETag: "5e95c66e-264"
Accept-Ranges: bytes

三、附加

附加一个sidecar形式的python脚本

#!/usr/bin/env python
# -*- encoding: utf8 -*-
"""
需求：nginx配置文件变化，自动更新配置文件，类似nginx -s reload
实现：
    1、用pyinotify实时监控nginx配置文件变化
    2、如果配置文件变化，给系统发送HUP来reload nginx
"""
import os
import re
import pyinotify
import logging
from threading import Timer
# Param
LOG_PATH = "/root/python/log"
CONF_PATHS = [
  "/etc/nginx",
]
DELAY = 5
SUDO = False
RELOAD_COMMAND = "nginx -s reload"
if SUDO:
  RELOAD_COMMAND = "sudo " + RELOAD_COMMAND
# Log
logger = logging.getLogger(__name__)
logger.setLevel(level = logging.INFO)
log_handler = logging.FileHandler(LOG_PATH)
log_handler.setLevel(logging.INFO)
log_formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
log_handler.setFormatter(log_formatter)
logger.addHandler(log_handler)
# Reloader
def reload_nginx():
  os.system(RELOAD_COMMAND)
  logger.info("nginx is reloaded")
t = Timer(DELAY, reload_nginx)
def trigger_reload_nginx(pathname, action):
  logger.info("nginx monitor is triggered because %s is %s" % (pathname, action))
  global t
  if t.is_alive():
    t.cancel()
    t = Timer(DELAY, reload_nginx)
    t.start()
  else:
    t = Timer(DELAY, reload_nginx)
    t.start()
events = pyinotify.IN_MODIFY | pyinotify.IN_CREATE | pyinotify.IN_DELETE
watcher = pyinotify.WatchManager()
watcher.add_watch(CONF_PATHS, events, rec=True, auto_add=True)
class EventHandler(pyinotify.ProcessEvent):
  def process_default(self, event):
    if event.name.endswith(".conf"):
      if event.mask == pyinotify.IN_CREATE:
        action = "created"
      if event.mask == pyinotify.IN_MODIFY:
        action = "modified"
      if event.mask == pyinotify.IN_DELETE:
        action = "deleted"
      trigger_reload_nginx(event.pathname, action)
handler = EventHandler()
notifier = pyinotify.Notifier(watcher, handler)
# Start
logger.info("Start Monitoring")
notifier.loop()