每天早上七点三十，准时推送干货

Hello 大家好，我是阿粉，前面的文章给大家介绍过 Nacos，用于服务注册发现和管理配置的开源组件，今天给大家分享另一个组件 Consul 也有相应的功能，我们一起来看一下吧！

背景

目前分布式系统架构已经基本普及，很多项目都是基于分布式架构的，以往的单机模式基本已经不适应当下互联网行业的发展。随着分布式项目的普及，项目服务实例数目的增加，服务的注册与发现功能就成了一项必不可少的架构。服务的注册与发现的功能，有很多开源方案。包括早期的zookeeper，百度的disconf，阿里的diamond，基于Go语言的ETCD，Spring集成的Eureka，以及前文提到的 Nacos 还有本文的主角Consul。这里不对上面提到的进行比较，本文仅介绍Consul，详细的对比，说明网上有很多资料，可以参考，例如：服务发现比较:Consul vs Zookeeper vs Etcd vs Eureka说到服务的注册与发现主要是下面两个主要功能：

服务注册与发现
配置中心即分布式项目统一配置管理

Consul 简介

Consul采用Go语言开发
Consul内置服务注册与发现框架、分布一致性协议实现、健康检查、Key/Value存储、多数据中心方案；不依赖其他工具，安装包包含一个可执行文件
支持DNS、HTTP协议接口
自带web-ui
Consul是 HashiCorp 公司推出的开源工具，用于实现分布式系统的服务发现与配置。
Consul支持两种服务注册的方式，一种是通过Consul的服务注册HTTP API，由服务自身在启动后调用API注册自己，另外一种则是通过在配置文件中定义服务的方式进行注册。Consul文档中建议使用后面一种方式来做服务配置和服务注册。

Consul 服务端配置使用

下载相应版本解压，并将可执行文件复制到/usr/local/consul目录下

创建一个service的配置文件

silence$ sudo mkdir /etc/consul.dsilence$ echo '{"service":{"name": "web", "tags": ["rails"], "port": 80}}' | sudo tee /etc/consul.d/web.json

启动代理
```
silence$ /usr/local/consul/consul agent -dev -node consul_01 -config-dir=/etc/consul.d/ -ui
```
-dev 参数代表本地测试环境启动；-node 参数表示自定义集群名称；-config-drir 参数表示services的注册配置文件目录，即上面创建的文件夹-ui 启动自带的web-ui管理页面

集群成员查询方式

silence-pro:~ silence$ /usr/local/consul/consul members

HTTP协议数据查询

silence-pro:~ silence$ curl http://127.0.0.1:8500/v1/catalog/service/web[    {        "ID": "ab1e3577-1b24-d254-f55e-9e8437956009",        "Node": "consul_01",        "Address": "127.0.0.1",        "Datacenter": "dc1",        "TaggedAddresses": {            "lan": "127.0.0.1",            "wan": "127.0.0.1"        },        "NodeMeta": {            "consul-network-segment": ""        },        "ServiceID": "web",        "ServiceName": "web",        "ServiceTags": [            "rails"],        "ServiceAddress": "",        "ServicePort": 80,        "ServiceEnableTagOverride": false,        "CreateIndex": 6,        "ModifyIndex": 6    }]silence-pro:~ silence$

web-ui管理

Consul Web UI

Consul的web-ui可以用来进行服务状态的查看，集群节点的检查，访问列表的控制以及KV存储系统的设置，相对于Eureka和ETCD，Consul的web-ui要好用的多。（Eureka和ETCD将在下一篇文章中简单介绍。）

7. KV存储的数据导入和导出

silence-pro:consul silence$ ./consul kv import @temp.json
silence-pro:consul silence$ ./consul kv export redis/

temp.json文件内容格式如下，一般是管理页面配置后先导出保存文件，以后需要再导入该文件

[    {        "key": "redis/config/password",        "flags": 0,        "value": "MTIzNDU2"    },    {        "key": "redis/config/username",        "flags": 0,        "value": "U2lsZW5jZQ=="    },    {        "key": "redis/zk/",        "flags": 0,        "value": ""    },    {        "key": "redis/zk/password",        "flags": 0,        "value": "NDU0NjU="    },    {        "key": "redis/zk/username",        "flags": 0,        "value": "ZGZhZHNm"    }]

Consul的KV存储系统是一种类似zk的树形节点结构，用来存储相关key/value键值对信息的，我们可以使用KV存储系统来实现上面提到的配置中心，将统一的配置信息保存在KV存储系统里面，方便各个实例获取并使用同一配置。而且更改配置后各个服务可以自动拉取最新配置，不需要重启服务。

Consul Java 客户端使用

maven pom依赖增加，版本可自由更换

<dependency>    <groupId>com.orbitz.consulgroupId>    <artifactId>consul-clientartifactId>    <version>0.12.3version>dependency><dependency>    <groupId>org.springframework.bootgroupId>    <artifactId>spring-boot-starter-actuatorartifactId>dependency>

Consul 基本工具类，根据需要相应扩展

package com.coocaa.consul.consul.demo;
import com.google.common.base.Optional;import com.google.common.net.HostAndPort;import com.orbitz.consul.*;import com.orbitz.consul.model.agent.ImmutableRegCheck;import com.orbitz.consul.model.agent.ImmutableRegistration;import com.orbitz.consul.model.health.ServiceHealth;
import java.net.MalformedURLException;import java.net.URI;import java.util.List;
public class ConsulUtil {
    private static Consul consul = Consul.builder().withHostAndPort(HostAndPort.fromString("127.0.0.1:8500")).build();
    /**
     * 服务注册
     */    public static void serviceRegister() {        AgentClient agent = consul.agentClient();
        try {            /**
             * 注意该注册接口：             * 需要提供一个健康检查的服务URL，以及每隔多长时间访问一下该服务（这里是3s）
             */            agent.register(8080, URI.create("http://localhost:8080/health").toURL(), 3, "tomcat", "tomcatID", "dev");
        } catch (MalformedURLException e) {            e.printStackTrace();        }
    }
    /**
     * 服务获取
     *
     * @param serviceName
     */    public static void findHealthyService(String serviceName) {        HealthClient healthClient = consul.healthClient();        List serviceHealthList = healthClient.getHealthyServiceInstances(serviceName).getResponse();        serviceHealthList.forEach((response) -> {            System.out.println(response);        });    }
    /**
     * 存储KV
     */    public static void storeKV(String key, String value) {        KeyValueClient kvClient = consul.keyValueClient();        kvClient.putValue(key, value);    }
    /**
     * 根据key获取value
     */    public static String getKV(String key) {        KeyValueClient kvClient = consul.keyValueClient();        Optional<String> value = kvClient.getValueAsString(key);        if (value.isPresent()) {            return value.get();        }        return "";    }
    /**
     * 找出一致性的节点（应该是同一个DC中的所有server节点）
     */    public static List<String> findRaftPeers() {        StatusClient statusClient = consul.statusClient();        return statusClient.getPeers();    }
    /**
     * 获取leader
     */    public static String findRaftLeader() {        StatusClient statusClient = consul.statusClient();        return statusClient.getLeader();    }
    public static void main(String[] args) {        AgentClient agentClient = consul.agentClient();        agentClient.deregister("tomcatID");    }}

temp.json 和 ConsulUtil.java 文件以及上传到 GitHub 资源库，回复【源码仓库】获取代码地址。

通过上面的基本工具类可以实现服务的注册和KV数据的获取与存储功能

Consul集群搭建

参考地址 Consul集群搭建 http://ju.outofmemory.cn/entry/189899

三台主机Consul下载安装，我这里没有物理主机，所以通过三台虚拟机来实现。虚拟机IP分192.168.231.145，192.168.231.146，192.168.231.147
将145和146两台主机作为Server模式启动，147作为Client模式启动，Server和Client只是针对Consul集群来说的，跟服务没有任何关系！

Server模式启动145，节点名称设为n1，数据中心统一用dc1

[root@centos145 consul]# ./consul agent -server -bootstrap-expect 2 -data-dir /tmp/consul -node=n1 -bind=192.168.231.145 -datacenter=dc1bootstrap_expect = 2: A cluster with 2 servers will provide no failure tolerance. See https://www.consul.io/docs/internals/consensus.html#deployment-tablebootstrap_expect > 0: expecting 2 servers==> Starting Consul agent...==> Consul agent running!           Version: 'v1.0.1'           Node ID: '6cc74ff7-7026-cbaa-5451-61f02114cd25'         Node name: 'n1'        Datacenter: 'dc1' (Segment: '')            Server: true (Bootstrap: false)       Client Addr: [127.0.0.1] (HTTP: 8500, HTTPS: -1, DNS: 8600)      Cluster Addr: 192.168.231.145 (LAN: 8301, WAN: 8302)           Encrypt: Gossip: false, TLS-Outgoing: false, TLS-Incoming: false
==> Log data will now stream in as it occurs:
    2017/12/06 23:26:21 [INFO] raft: Initial configuration (index=0): []    2017/12/06 23:26:21 [INFO] serf: EventMemberJoin: n1.dc1 192.168.231.145    2017/12/06 23:26:21 [INFO] serf: EventMemberJoin: n1 192.168.231.145    2017/12/06 23:26:21 [INFO] agent: Started DNS server 127.0.0.1:8600 (udp)    2017/12/06 23:26:21 [INFO] raft: Node at 192.168.231.145:8300 [Follower] entering Follower state (Leader: "")    2017/12/06 23:26:21 [INFO] consul: Adding LAN server n1 (Addr: tcp/192.168.231.145:8300) (DC: dc1)    2017/12/06 23:26:21 [INFO] consul: Handled member-join event for server "n1.dc1" in area "wan"    2017/12/06 23:26:21 [INFO] agent: Started DNS server 127.0.0.1:8600 (tcp)    2017/12/06 23:26:21 [INFO] agent: Started HTTP server on 127.0.0.1:8500 (tcp)    2017/12/06 23:26:21 [INFO] agent: started state syncer    2017/12/06 23:26:28 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:26:30 [WARN] raft: no known peers, aborting election    2017/12/06 23:26:49 [ERR] agent: Coordinate update error: No cluster leader    2017/12/06 23:26:54 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:27:24 [ERR] agent: Coordinate update error: No cluster leader    2017/12/06 23:27:27 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:27:56 [ERR] agent: Coordinate update error: No cluster leader    2017/12/06 23:28:02 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:28:27 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:28:33 [ERR] agent: Coordinate update error: No cluster leader

目前只启动了145，所以还没有集群

Server模式启动146，节点名称用n2，并在n2上启用了web-ui管理页面功能

[root@centos146 consul]# ./consul agent -server -bootstrap-expect 2 -data-dir /tmp/consul -node=n2 -bind=192.168.231.146 -datacenter=dc1 -uibootstrap_expect = 2: A cluster with 2 servers will provide no failure tolerance. See https://www.consul.io/docs/internals/consensus.html#deployment-tablebootstrap_expect > 0: expecting 2 servers==> Starting Consul agent...==> Consul agent running!           Version: 'v1.0.1'           Node ID: 'eb083280-c403-668f-e193-60805c7c856a'         Node name: 'n2'        Datacenter: 'dc1' (Segment: '')            Server: true (Bootstrap: false)       Client Addr: [127.0.0.1] (HTTP: 8500, HTTPS: -1, DNS: 8600)      Cluster Addr: 192.168.231.146 (LAN: 8301, WAN: 8302)           Encrypt: Gossip: false, TLS-Outgoing: false, TLS-Incoming: false
==> Log data will now stream in as it occurs:
    2017/12/06 23:28:30 [INFO] raft: Initial configuration (index=0): []    2017/12/06 23:28:30 [INFO] serf: EventMemberJoin: n2.dc1 192.168.231.146    2017/12/06 23:28:31 [INFO] serf: EventMemberJoin: n2 192.168.231.146    2017/12/06 23:28:31 [INFO] raft: Node at 192.168.231.146:8300 [Follower] entering Follower state (Leader: "")    2017/12/06 23:28:31 [INFO] consul: Adding LAN server n2 (Addr: tcp/192.168.231.146:8300) (DC: dc1)    2017/12/06 23:28:31 [INFO] consul: Handled member-join event for server "n2.dc1" in area "wan"    2017/12/06 23:28:31 [INFO] agent: Started DNS server 127.0.0.1:8600 (tcp)    2017/12/06 23:28:31 [INFO] agent: Started DNS server 127.0.0.1:8600 (udp)    2017/12/06 23:28:31 [INFO] agent: Started HTTP server on 127.0.0.1:8500 (tcp)    2017/12/06 23:28:31 [INFO] agent: started state syncer    2017/12/06 23:28:38 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:28:39 [WARN] raft: no known peers, aborting election    2017/12/06 23:28:57 [ERR] agent: Coordinate update error: No cluster leader    2017/12/06 23:29:11 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:29:30 [ERR] agent: Coordinate update error: No cluster leader    2017/12/06 23:29:38 [ERR] agent: failed to sync remote state: No cluster leader    2017/12/06 23:29:57 [ERR] agent: Coordinate update error: No cluster leader

同样没有集群发现，此时n1和n2都启动起来，但是互相并不知道集群的存在！

将n1节点加入n2
```
[silence@centos145 consul]$ ./consul join 192.168.231.146
```
此时n1和n2都打印发现了集群的日志信息
这个时候n1和n2两个节点已经是一个集群里面的Server模式的节点了

Client模式启动147

[root@centos147 consul]# ./consul agent -data-dir /tmp/consul -node=n3 -bind=192.168.231.147 -datacenter=dc1==> Starting Consul agent...==> Consul agent running!           Version: 'v1.0.1'           Node ID: 'be7132c3-643e-e5a2-9c34-cad99063a30e'         Node name: 'n3'        Datacenter: 'dc1' (Segment: '')            Server: false (Bootstrap: false)       Client Addr: [127.0.0.1] (HTTP: 8500, HTTPS: -1, DNS: 8600)      Cluster Addr: 192.168.231.147 (LAN: 8301, WAN: 8302)           Encrypt: Gossip: false, TLS-Outgoing: false, TLS-Incoming: false
==> Log data will now stream in as it occurs:
    2017/12/06 23:36:46 [INFO] serf: EventMemberJoin: n3 192.168.231.147    2017/12/06 23:36:46 [INFO] agent: Started DNS server 127.0.0.1:8600 (udp)    2017/12/06 23:36:46 [INFO] agent: Started DNS server 127.0.0.1:8600 (tcp)    2017/12/06 23:36:46 [INFO] agent: Started HTTP server on 127.0.0.1:8500 (tcp)    2017/12/06 23:36:46 [INFO] agent: started state syncer    2017/12/06 23:36:46 [WARN] manager: No servers available    2017/12/06 23:36:46 [ERR] agent: failed to sync remote state: No known Consul servers    2017/12/06 23:37:08 [WARN] manager: No servers available    2017/12/06 23:37:08 [ERR] agent: failed to sync remote state: No known Consul servers    2017/12/06 23:37:36 [WARN] manager: No servers available    2017/12/06 23:37:36 [ERR] agent: failed to sync remote state: No known Consul servers    2017/12/06 23:38:02 [WARN] manager: No servers available    2017/12/06 23:38:02 [ERR] agent: failed to sync remote state: No known Consul servers    2017/12/06 23:38:22 [WARN] manager: No servers available    2017/12/06 23:38:22 [ERR] agent: failed to sync remote state: No known Consul servers

在n3上面将节点n3加入集群

[silence@centos147 consul]$ ./consul join 192.168.231.145

再次查看集群节点信息
此时三个节点的Consul集群搭建成功了！其实n1和n2是Server模式启动，n3是Client模式启动。
关于Consul的Server模式和Client模式主要的区别是这样的，一个Consul集群通过启动的参数-bootstrap-expect来控制这个集群的Server节点个数，Server模式的节点会维护集群的状态，并且如果某个Server节点退出了集群，则会触发Leader重新选举机制，在会剩余的Server模式节点中重新选举一个Leader；而Client模式的节点的加入和退出很自由。
在n2中启动web-ui