详解ZooKeeper在微服务注册中心的应用

本文分享自华为云社区《SpringCloud ZooKeeper 详解，以及与Go、Rust等非Java服务的集成》，作者： 张俭。

ZooKeeper，是一个开源的分布式协调服务，不仅支持分布式选举、任务分配，还可以用于微服务的注册中心和配置中心。本文，我们将深入探讨ZooKeeper用做微服务注册中心的场景。

ZooKeeper中的服务注册路径

SpringCloud ZooKeeper遵循特定的路径结构进行服务注册

/services/${spring.application.name}/${serviceId}

示例：

/services/provider-service/d87a3891-1173-45a0-bdfa-a1b60c71ef4e

/services和/${spring.application.name}是ZooKeeper中的永久节点，/${serviceId}是临时节点，当服务下线时，ZooKeeper会自动删除该节点。

注：当微服务的最后一个实例下线时，SpringCloud ZooKeeper框架会删除/${spring.application.name}节点。

ZooKeeper中的服务注册数据

下面是一个典型的服务注册内容示例：

{"name":"provider-service","id":"d87a3891-1173-45a0-bdfa-a1b60c71ef4e","address":"192.168.0.105","port":8080,"sslPort":null,"payload":{"@class":"org.springframework.cloud.zookeeper.discovery.ZookeeperInstance","id":"provider-service","name":"provider-service","metadata":{"instance_status":"UP"}},"registrationTimeUTC":1695401004882,"serviceType":"DYNAMIC","uriSpec":{"parts":[{"value":"scheme","variable":true},{"value":"://","variable":false},{"value":"address","variable":true},{"value":":","variable":false},{"value":"port","variable":true}]}}

其中，address、port和uriSpec是最核心的数据。uriSpec中的parts区分了哪些内容是可变的，哪些是固定的。

SpringCloud 服务使用OpenFeign互相调用

一旦两个微服务都注册到了ZooKeeper，那么它们就可以通过OpenFeign互相调用了。简单的示例如下

服务提供者创建SpringBoot项目

创建SpringBoot项目，并添加spring-cloud-starter-zookeeper-discovery和spring-boot-starter-web依赖。

配置application.yaml

spring:application:name: provider-servicecloud:zookeeper:connect-string: localhost:2181server:port: 8082

注册到ZooKeeper

在启动类上添加@EnableDiscoveryClient注解。

创建一个简单的REST接口

@RestControllerpublic class ProviderController {@GetMapping("/hello")public String hello() {return "Hello from Provider Service!";}}

服务消费者创建SpringBoot项目

创建SpringBoot项目，并添加spring-cloud-starter-zookeeper-discovery、spring-cloud-starter-openfeign和spring-boot-starter-web依赖。

配置application.yaml

spring:application:name: consumer-servicecloud:zookeeper:connect-string: localhost:2181server:port: 8081

注册到ZooKeeper

在启动类上添加@EnableDiscoveryClient注解。

创建一个REST接口，通过OpenFeign调用服务提供者

@RestControllerpublic class ConsumerController {@Autowiredprivate ProviderClient providerClient;@GetMapping("/getHello")public String getHello() {return providerClient.hello();}}

运行效果

curl localhost:8081/getHello -iHTTP/1.1 200Content-Type: text/plain;charset=UTF-8Content-Length: 28Date: Wed, 18 Oct 2023 02:40:57 GMTHello from Provider Service!

非Java服务在SpringCloud ZooKeeper中注册

可能有些读者乍一看觉得有点奇怪，为什么要在SpringCloud ZooKeeper中注册非Java服务呢？没有这个应用场景。

当然，这样的场景比较少，常见于大部分项目都是用SpringCloud开发，但有少部分项目因为种种原因，不得不使用其他语言开发，比如Go、Rust等。这时候，我们就需要在SpringCloud ZooKeeper中注册非Java服务了。

对于非JVM语言开发的服务，只需确保它们提供了Rest/HTTP接口并正确地注册到ZooKeeper，就可以被SpringCloud的Feign客户端所调用。

Go服务在SpringCloud ZooKeeper

example代码组织：

├── consumer│ └── consumer.go├── go.mod├── go.sum└── provider└── provider.go

Go服务提供者在SpringCloud ZooKeeper

注：该代码的质量为demo级别，实际生产环境需要更加严谨的代码，如重连机制、超时机制、更优秀的服务ID生成算法等。

package mainimport ("fmt""log""net/http""time""encoding/json""github.com/gin-gonic/gin""github.com/samuel/go-zookeeper/zk")const (zkServers = "localhost:2181" // Zookeeper服务器地址)func main() {// 初始化gin框架r := gin.Default()// 添加一个简单的hello接口r.GET("/hello", func(c *gin.Context) {c.String(http.StatusOK, "Hello from Go service!")})// 注册服务到zookeeperregisterToZookeeper()// 启动gin服务器r.Run(":8080")}func registerToZookeeper() {conn, _, err := zk.Connect([]string{zkServers}, time.Second*5)if err != nil {panic(err)}// 检查并创建父级路径ensurePathExists(conn, "/services")ensurePathExists(conn, "/services/provider-service")// 构建注册的数据data, _ := json.Marshal(map[string]interface{}{"name": "provider-service","address": "127.0.0.1","port": 8080,"sslPort": nil,"payload": map[string]interface{}{"@class": "org.springframework.cloud.zookeeper.discovery.ZookeeperInstance", "id": "provider-service", "name": "provider-service", "metadata": map[string]string{"instance_status": "UP"}},"serviceType": "DYNAMIC","uriSpec": map[string]interface{}{"parts": []map[string]interface{}{{"value": "scheme", "variable": true},{"value": "://", "variable": false},{"value": "address", "variable": true},{"value": ":", "variable": false},{"value": "port", "variable": true},},},})// 在zookeeper中注册服务path := "/services/provider-service/" + generateServiceId()_, err = conn.Create(path, data, zk.FlagEphemeral, zk.WorldACL(zk.PermAll))if err != nil {log.Fatalf("register service error: %s", err)} else {log.Println(path)}}func ensurePathExists(conn *zk.Conn, path string) {exists, _, err := conn.Exists(path)if err != nil {log.Fatalf("check path error: %s", err)}if !exists {_, err := conn.Create(path, []byte{}, 0, zk.WorldACL(zk.PermAll))if err != nil {log.Fatalf("create path error: %s", err)}}}func generateServiceId() string {// 这里简化为使用当前时间生成ID，实际生产环境可能需要更复杂的算法return fmt.Sprintf("%d", time.Now().UnixNano())}

调用效果

curl localhost:8081/getHello -iHTTP/1.1 200Content-Type: text/plain;charset=UTF-8Content-Length: 28Date: Wed, 18 Oct 2023 02:43:52 GMTHello from Go Service!

Go服务消费者在SpringCloud ZooKeeper

package mainimport ("encoding/json""fmt""io""log""net/http""time""github.com/samuel/go-zookeeper/zk")const (zkServers = "localhost:2181" // Zookeeper服务器地址)var conn *zk.Connfunc main() {// 初始化ZooKeeper连接initializeZookeeper()// 获取服务信息serviceInfo := getServiceInfo("/services/provider-service")fmt.Println("Fetched service info:", serviceInfo)port := int(serviceInfo["port"].(float64))resp, err := http.Get(fmt.Sprintf("http://%s:%d/hello", serviceInfo["address"], port))if err != nil {panic(err)}body, err := io.ReadAll(resp.Body)if err != nil {panic(err)}fmt.Println(string(body))}func initializeZookeeper() {var err errorconn, _, err = zk.Connect([]string{zkServers}, time.Second*5)if err != nil {log.Fatalf("Failed to connect to ZooKeeper: %s", err)}}func getServiceInfo(path string) map[string]interface{} {children, _, err := conn.Children(path)if err != nil {log.Fatalf("Failed to get children of %s: %s", path, err)}if len(children) == 0 {log.Fatalf("No services found under %s", path)}// 这里只获取第一个服务节点的信息作为示例，实际上可以根据负载均衡策略选择一个服务节点data, _, err := conn.Get(fmt.Sprintf("%s/%s", path, children[0]))if err != nil {log.Fatalf("Failed to get data of %s: %s", children[0], err)}var serviceInfo map[string]interface{}if err := json.Unmarshal(data, &serviceInfo); err != nil {log.Fatalf("Failed to unmarshal data: %s", err)}return serviceInfo}

Rust服务在SpringCloud ZooKeeper

example代码组织：

├── Cargo.lock├── Cargo.toml└── src└── bin├── consumer.rs└── provider.rs

Rust服务提供者在SpringCloud ZooKeeper

use std::collections::HashMap;use std::time::Duration;use serde_json::Value;use warp::Filter;use zookeeper::{Acl, CreateMode, WatchedEvent, Watcher, ZooKeeper};static ZK_SERVERS: &str = "localhost:2181";static mut ZK_CONN: Option = None;struct LoggingWatcher;impl Watcher for LoggingWatcher {fn handle(&self, e: WatchedEvent) {println!("WatchedEvent: {:?}", e);}}#[tokio::main]async fn main() {let hello = warp::path!("hello").map(|| warp::reply::html("Hello from Rust service!"));register_to_zookeeper().await;warp::serve(hello).run(([127, 0, 0, 1], 8083)).await;}async fn register_to_zookeeper() {unsafe {ZK_CONN = Some(ZooKeeper::connect(ZK_SERVERS, Duration::from_secs(5), LoggingWatcher).unwrap());let zk = ZK_CONN.as_ref().unwrap();let path = "/services/provider-service";if zk.exists(path, false).unwrap().is_none() {zk.create(path, vec![], Acl::open_unsafe().clone(), CreateMode::Persistent).unwrap();}let service_data = get_service_data();let service_path = format!("{}/{}", path, generate_service_id());zk.create(&service_path, service_data, Acl::open_unsafe().clone(), CreateMode::Ephemeral).unwrap();}}fn get_service_data() -> Vec {let mut data: HashMap = HashMap::new();data.insert("name", serde_json::Value::String("provider-service".to_string()));data.insert("address", serde_json::Value::String("127.0.0.1".to_string()));data.insert("port", serde_json::Value::Number(8083.into()));serde_json::to_vec(&data).unwrap()}fn generate_service_id() -> String {format!("{}", chrono::Utc::now().timestamp_nanos())}

Rust服务消费者在SpringCloud ZooKeeper

use std::collections::HashMap;use std::time::Duration;use zookeeper::{WatchedEvent, Watcher, ZooKeeper};use reqwest;use serde_json::Value;static ZK_SERVERS: &str = "localhost:2181";struct LoggingWatcher;impl Watcher for LoggingWatcher {fn handle(&self, e: WatchedEvent) {println!("WatchedEvent: {:?}", e);}}#[tokio::main]async fn main() {let provider_data = fetch_provider_data_from_zookeeper().await;let response = request_provider(&provider_data).await;println!("Response from provider: {}", response);}async fn fetch_provider_data_from_zookeeper() -> HashMap {let zk = ZooKeeper::connect(ZK_SERVERS, Duration::from_secs(5), LoggingWatcher).unwrap();let children = zk.get_children("/services/provider-service", false).unwrap();if children.is_empty() {panic!("No provider services found!");}// For simplicity, we just take the first child (i.e., service instance).// In a real-world scenario, load balancing strategies would determine which service instance to use.let data = zk.get_data(&format!("/services/provider-service/{}", children[0]), false).unwrap();serde_json::from_slice(&data.0).unwrap()}async fn request_provider(provider_data: &HashMap) -> String {let address = provider_data.get("address").unwrap().as_str().unwrap();let port = provider_data.get("port").unwrap().as_i64().unwrap();let url = format!("http://{}:{}/hello", address, port);let response = reqwest::get(&url).await.unwrap();response.text().await.unwrap()}

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