viper配置框架的介绍支持zookeeper的读取和监听

viper作为配置框架，其功能非常的强大，我们没有理由不去了解一下。我们先看官网对它的功能简介：

viper是完整配置解决方案，他可以处理所有类型和格式的配置文件，他有如下功能：

• 设置默认配置
• 支持读取 JSON TOML YAML HCL 和 Java 属性配置文件
• 监听配置文件变化，实时读取读取配置文件内容
• 读取环境变量值
• 读取远程配置系统 (etcd Consul) 和监控配置变化
• 读取命令 Flag 值
• 读取 buffer 值
• 读取确切值

乍一看，未免有相见恨晚之感，可仔细一想，不免脑袋里有另外一种声音：不会不支持读取 zookeeper 吧？好吧，至少我是这样的。

基于这种想法，当然要去立马尝试，如下：

viper.AddRemoteProvider("zookeeper", "xx.xx.xx.xx:2181", "/viper/test")

返回结果是：

Unsupported Remote Provider Type zookeeper

果不其然，于是追踪 viper.AddRemoteProvider 的源码，发现viper只支持如下几种

var SupportedRemoteProviders = []string{"etcd", "consul", "firestore"}

如果就此打住，未免有点太可惜，作为偏执狂，总想着能否来改造下viper，让其支持 zookeeper ，于是在issue上找是否有人遇到同样的问题，还整让我找到了， 传送 。但是不完整，且稍微有点bug。所以根据他的基础上，我做了些调整。进入正题，我们开始修改viper源码。说明下，我的viper版本是最新的 1.7.0

修改源码

1、添加zookeeper.go

添加的位置： github.com/bketelsen/crypt/zookeeper , zookeeper 目录需要自己创建， github.com/bketelsen/crypt 是viper的依赖包，会自动下载

文件内容：

package zookeeper

import (
	"errors"
	"fmt"
	zk "github.com/samuel/go-zookeeper/zk"
	//"github.com/xordataexchange/crypt/backend"
	"github.com/bketelsen/crypt/backend"
	"strings"
	"time"
)

type Client struct {
	client *zk.Conn
	waitIndex uint64
}

func New(machines []string) (*Client, error) {
	zkclient, _, err := zk.Connect(machines, time.Second)
	if err != nil {
		return nil, err
	}
	return &Client{zkclient, 0}, nil
}

func (c *Client) Get(key string) ([]byte, error) {
	resp, _, err := c.client.Get(key)
	if err != nil {
		return nil, err
	}
	return []byte(resp), nil
}

func nodeWalk(prefix string, c *Client, vars map[string]string) error {
	l, stat, err := c.client.Children(prefix)
	if err != nil {
		return err
	}

	if stat.NumChildren == 0 {
		b, _, err := c.client.Get(prefix)
		if err != nil {
			return err
		}
		vars[prefix] = string(b)

	} else {
		for _, key := range l {
			s := prefix + "/" + key
			_, stat, err := c.client.Exists(s)
			if err != nil {
				return err
			}
			if stat.NumChildren == 0 {
				b, _, err := c.client.Get(s)
				if err != nil {
					return err
				}
				vars[s] = string(b)
			} else {
				nodeWalk(s, c, vars)
			}
		}
	}
	return nil
}

func (c *Client) GetValues(key string, keys []string) (map[string]string, error) {
	vars := make(map[string]string)
	for _, v := range keys {
		v = fmt.Sprintf("%s/%s", key, v)
		v = strings.Replace(v, "/*", "", -1)
		_, _, err := c.client.Exists(v)
		if err != nil {
			return vars, err
		}
		if v == "/" {
			v = ""
		}
		err = nodeWalk(v, c, vars)
		if err != nil {
			return vars, err
		}
	}
	return vars, nil
}

func (c *Client) List(key string) (backend.KVPairs, error) {
	var list backend.KVPairs
	resp, stat, err := c.client.Children(key)
	if err != nil {
		return nil, err
	}

	if stat.NumChildren == 0 {
		return list, nil
	}

	entries, err := c.GetValues(key, resp)
	if err != nil {
		return nil, err
	}

	for k, v := range entries {
		list = append(list, &backend.KVPair{Key: k, Value: []byte(v)})
	}
	return list, nil
}

func (c *Client) createParents(key string) error {
	flags := int32(0)
	acl := zk.WorldACL(zk.PermAll)

	if key[0] != '/' {
		return errors.New("Invalid path")
	}

	payload := []byte("")
	pathString := ""
	pathNodes := strings.Split(key, "/")
	for i := 1; i < len(pathNodes); i++ {
		pathString += "/" + pathNodes[i]
		_, err := c.client.Create(pathString, payload, flags, acl)
		// not being able to create the node because it exists or not having
		// sufficient rights is not an issue. It is ok for the node to already
		// exist and/or us to only have read rights
		if err != nil && err != zk.ErrNodeExists && err != zk.ErrNoAuth {
			return err
		}
	}
	return nil
}

func (c *Client) Set(key string, value []byte) error {
	err := c.createParents(key)
	if err != nil {
		return err
	}
	_, err = c.client.Set(key, []byte(value), -1)
	return err
}

func (c *Client) Watch(key string, stop chan bool) <-chan *backend.Response {
	respChan := make(chan *backend.Response, 0)
	go func() {
		for {
			resp, _, watch, err := c.client.GetW(key)
			if err != nil {
				respChan <- &backend.Response{nil, err}
				time.Sleep(time.Second * 5)
			}

			select {
			case e := <-watch:
				if e.Type == zk.EventNodeDataChanged {
					resp, _, err = c.client.Get(key)
					if err != nil {
						respChan <- &backend.Response{nil, err}
					}
					c.waitIndex = 0
					respChan <- &backend.Response{[]byte(resp), nil}
				}
			}
		}
	}()
	return respChan
}

这个文件是实现 ConfigManager 接口，我们在上图中看到 etcd ， consul ， filestore ，均有实现该接口，接口的定义很简单

type ConfigManager interface {
	Get(key string) ([]byte, error)
	List(key string) (KVPairs, error)
	Set(key string, value []byte) error
	Watch(key string, stop chan bool) <-chan *Response
}

2、修改config.go

文件的位置： github.com/bketelsen/crypt/config/config.go ，如下图

在 func NewStandardEtcdConfigManager(machines []string) (ConfigManager, error) 方法下面添加如下方法：

// NewStandardZookeeperConfigManager returns a new ConfigManager backed by Zookeeper.
// Data will be encrypted.
func NewStandardZookeeperConfigManager(machines []string) (ConfigManager, error) {
	store, err := zookeeper.New(machines)
	if err != nil {
		return nil, err
	}
	return NewStandardConfigManager(store)
}

在 func NewEtcdConfigManager(machines []string, keystore io.Reader) (ConfigManager, error) 方法下面添加如下方法：

// NewZookeeperConfigManager returns a new ConfigManager backed by zookeeper.
// Data will be encrypted.
func NewZookeeperConfigManager(machines []string, keystore io.Reader) (ConfigManager, error) {
	store, err := zookeeper.New(machines)
	if err != nil {
		return nil, err
	}
	return NewConfigManager(store, keystore)
}

这两个方法是初始化 ConfigManager 对象，也就是我们刚才添加的 zookeeper.go 文件的对象

3、修改remote.go

文件的位置： github.com/spf13/viper/remote/remote.go ,如下图

找到74行，用下面的代码替换 func getConfigManager(rp viper.RemoteProvider) (crypt.ConfigManager, error) 方法

func getConfigManager(rp viper.RemoteProvider) (crypt.ConfigManager, error) {
	var cm crypt.ConfigManager
	var err error

	if rp.SecretKeyring() != "" {
		var kr *os.File
		kr, err = os.Open(rp.SecretKeyring())
		if err != nil {
			return nil, err
		}
		defer kr.Close()
		switch rp.Provider() {
		case "etcd":
			cm, err = crypt.NewEtcdConfigManager([]string{rp.Endpoint()}, kr)
		case "zookeeper":
			cm, err = crypt.NewZookeeperConfigManager([]string{rp.Endpoint()}, kr)
		case "firestore":
			cm, err = crypt.NewFirestoreConfigManager([]string{rp.Endpoint()}, kr)
		default:
			cm, err = crypt.NewConsulConfigManager([]string{rp.Endpoint()}, kr)
		}
	} else {
		switch rp.Provider() {
		case "etcd":
			cm, err = crypt.NewStandardEtcdConfigManager([]string{rp.Endpoint()})
		case "zookeeper":
			cm, err = crypt.NewStandardZookeeperConfigManager([]string{rp.Endpoint()})
		case "firestore":
			cm, err = crypt.NewStandardFirestoreConfigManager([]string{rp.Endpoint()})
		default:
			cm, err = crypt.NewStandardConsulConfigManager([]string{rp.Endpoint()})
		}
	}
	if err != nil {
		return nil, err
	}
	return cm, nil
}

细心的读者可能已经发现，其实就添加了两个case选项：

4、修改viper.go

文件的位置： github.com/spf13/viper/viper.go ,如下图

取+监听zookeeper(1)\image-20200521222843002.png)

找到两个 SupportedRemoteProviders 定义的定法，1.7.0版本的行号分别是：290，331。只要添加 zookeeper ,即可

SupportedRemoteProviders = []string{"etcd", "consul", "firestore", "zookeeper"}

好了，修改代码的工作已经完了，接下来我们来测试：

测试

注意：zookeeper中已经设置了内容

set /viper/test {"appName":"test","nodes":["127.0.0.1","127.0.0.2","127.0.0.3"]}

package main

import (
	"fmt"
	"github.com/fsnotify/fsnotify"
	"github.com/spf13/viper"
	_ "github.com/spf13/viper/remote"
	"time"
)


type config struct {
	AppName string
	Nodes []string
}

func main() {
	var waitGroup=sync.WaitGroup{}
	waitGroup.Add(1)
	readRemoteZookeeper()
	go watchRemoteZookeeper()
	waitGroup.Wait()
}

func readRemoteZookeeper() {
	viper.AddRemoteProvider("zookeeper", "62.234.15.24:2181", "/viper/test")
	viper.SetConfigType("json") 
	err := viper.ReadRemoteConfig()
	if err != nil {
		panic(fmt.Sprintf("read remote zookeeper error:+%v", err))
	}

	var C config
	viper.Unmarshal(&C)
	fmt.Printf("从zookeeper读取配置内容:%+v\n", C)
}

func watchRemoteZookeeper() {
	go func() {
		for {
  //delay after each request
			time.Sleep(time.Second * 5)
			err := viper.WatchRemoteConfig()
			if err != nil {
				fmt.Errorf("unable to read remote config: %v", err)
				continue
			}
			fmt.Printf("从zookeeper读取更新内容:appName=%s,nodes=%+v\n", viper.Get("appName"), viper.Get("nodes"))
		}
	}()
}

输出内容：

从zookeeper读取配置内容:{AppName:test Nodes:[127.0.0.1 127.0.0.2 127.0.0.3]}
从zookeeper读取更新内容:appName=test,nodes=[127.0.0.1 127.0.0.2 127.0.0.3]

如果我们修改zookeeper的内容，则viper会读取到更新后的内容：

set /viper/test {"appName":"test","nodes":["127.0.0.1","127.0.0.2","127.0.0.3","127.0.0.4"]}

从zookeeper读取更新内容:appName=test,nodes=[127.0.0.1 127.0.0.2 127.0.0.3 127.0.0.4]

结语

让viper支持 zookeeper 并不复杂的，并且基本上不需要修改原有的方法， 这要归结于viper用到一个非常重要的设计原则： 开闭原则 ，读者可以自行体会。

关于viper的基本使用， github 已经有非常详细的例子，这里就不再赘述，如有疑问，可以私信我

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