本文介绍Ocelot中的服务发现（Service Discovery），Ocelot允许指定一个服务发现提供器，之后将从中寻找下游服务的host和port来进行请求路由。
关于服务发现的详细介绍请点击。
在Ocelot中使用了Consul作为服务发现的provider。

1、Consul下载安装

从官方下载页选择合适的平台下载，解压出一个二进制文件并保存到相应位置，并将路径存入path中，本文以windows版本为例（其他平台操作类似）。
打开 cmd/powershell 运行 consul agent -dev 输出如下文本表示成功以dev方式启动consul

==> Starting Consul agent...

==> Consul agent running!

           Version: 'v1.0.7'

           Node ID: '3fc1edca-b635-56cc-b767-01a942423f73'

         Node name: 'Weidaicheng-PC'

        Datacenter: 'dc1' (Segment: '<all>')

            Server: true (Bootstrap: false)

       Client Addr: [127.0.0.1] (HTTP: 8500, HTTPS: -1, DNS: 8600)

      Cluster Addr: 127.0.0.1 (LAN: 8301, WAN: 8302)

           Encrypt: Gossip: false, TLS-Outgoing: false, TLS-Incoming: false

==> Log data will now stream in as it occurs:

    2018/04/29 09:22:03 [DEBUG] agent: Using random ID "3fc1edca-b635-56cc-b767-01a942423f73" as node ID

    2018/04/29 09:22:03 [INFO] raft: Initial configuration (index=1): [{Suffrage:Voter ID:3fc1edca-b635-56cc-b767-01a942423f73 Address:127.0.0.1:8300}]

    2018/04/29 09:22:03 [INFO] raft: Node at 127.0.0.1:8300 [Follower] entering Follower state (Leader: "")

    2018/04/29 09:22:03 [INFO] serf: EventMemberJoin: Weidaicheng-PC.dc1 127.0.0.1

    2018/04/29 09:22:03 [INFO] serf: EventMemberJoin: Weidaicheng-PC 127.0.0.1

    2018/04/29 09:22:03 [INFO] consul: Adding LAN server Weidaicheng-PC (Addr: tcp/127.0.0.1:8300) (DC: dc1)

    2018/04/29 09:22:03 [INFO] consul: Handled member-join event for server "Weidaicheng-PC.dc1" in area "wan"

    2018/04/29 09:22:03 [INFO] agent: Started DNS server 127.0.0.1:8600 (udp)

    2018/04/29 09:22:03 [INFO] agent: Started DNS server 127.0.0.1:8600 (tcp)

    2018/04/29 09:22:03 [INFO] agent: Started HTTP server on 127.0.0.1:8500 (tcp)

    2018/04/29 09:22:03 [INFO] agent: started state syncer

    2018/04/29 09:22:03 [WARN] raft: Heartbeat timeout from "" reached, starting election

    2018/04/29 09:22:03 [INFO] raft: Node at 127.0.0.1:8300 [Candidate] entering Candidate state in term 2

    2018/04/29 09:22:03 [DEBUG] raft: Votes needed: 1

    2018/04/29 09:22:03 [DEBUG] raft: Vote granted from 3fc1edca-b635-56cc-b767-01a942423f73 in term 2. Tally: 1

    2018/04/29 09:22:03 [INFO] raft: Election won. Tally: 1

    2018/04/29 09:22:03 [INFO] raft: Node at 127.0.0.1:8300 [Leader] entering Leader state

    2018/04/29 09:22:03 [INFO] consul: cluster leadership acquired

    2018/04/29 09:22:03 [INFO] consul: New leader elected: Weidaicheng-PC

    2018/04/29 09:22:03 [DEBUG] consul: Skipping self join check for "Weidaicheng-PC" since the cluster is too small

    2018/04/29 09:22:03 [INFO] consul: member 'Weidaicheng-PC' joined, marking health alive

    2018/04/29 09:22:03 [DEBUG] agent: Skipping remote check "serfHealth" since it is managed automatically

    2018/04/29 09:22:03 [INFO] agent: Synced node info

    2018/04/29 09:22:03 [DEBUG] agent: Node info in sync

    2018/04/29 09:22:04 [DEBUG] agent: Skipping remote check "serfHealth" since it is managed automatically

    2018/04/29 09:22:04 [DEBUG] agent: Node info in sync

浏览器输入http://localhost:8500可以看到UI后台界面

Consul UI.png

或者打开另一个PowerShell输入 consul members 输出如下

Node            Address         Status  Type    Build  Protocol  DC   Segment

Weidaicheng-PC  127.0.0.1:8301  alive   server  1.0.7  2         dc1  <all>

至此，Consul安装完成

2、代码修改

继续使用上一篇的项目，在WebApiA和WebApiB中分别新建一个api控制器 CounterController 代码如下

//WebApiA

using Microsoft.AspNetCore.Mvc;

namespace WebApiA.Controllers

{

    [Produces("application/json")]

    [Route("api/[controller]/[action]")]

    public class CounterController : Controller

    {

        private static int _count = 0;

        [HttpGet]

        public string Count()

        {

            return $"Count {++_count} from WebapiA";

        }

    }

}

//WebApiB

using Microsoft.AspNetCore.Mvc;

namespace WebApiB.Controllers

{

    [Produces("application/json")]

    [Route("api/[controller]/[action]")]

    public class CounterController : Controller

    {

        private static int _count = 0;

        [HttpGet]

        public string Count()

        {

            return $"Count {++_count} from WebapiB";

        }

    }

}

修改OcelotGetway项目中的配置文件 configuration.json
在 ReRoutes 节点中添加

{

      "DownstreamPathTemplate": "/api/Counter/Count",

      "DownstreamScheme": "http",

      "UpstreamPathTemplate": "/count",

      "UpstreamHttpMethod": [ "Get" ],

      "ServiceName": "Count",

      "LoadBalancer": "RoundRobin",

      "UseServiceDiscovery": true

}

其中，ServiceName指定服务发现的服务名称，在之后Consul中注册服务的时候会用到，LoadBalancer指定使用的负载均衡模式（目前Ocelot仅支持时间片轮询(RoundRobin)和最少连接(LeastConnection)模式），UseServiceDiscovery标志使用服务发现。
注：如果不指定负载均衡，将不使用负载均衡，本文中使用时间片轮询为例。
然后再根节点添加全局配置

"GlobalConfiguration": {

    "ServiceDiscoveryProvider": {

      "Host": "localhost",

      "Port": 8500

    }

  }

指定服务发现提供器的位置。目前Ocelot只支持共用一个provider。

3、注册服务

在consul所在的目录下创建文件夹 consul.d，文件夹位置及文件夹名称可以随意，进入consul.d文件夹中创建两个json文件 Count_1.json 和 Count_2.json，分别添加如下文本

{

    "service": {

        "id": "count1",

        "name": "Count",

        "tags": ["dev"],

        "address": "localhost",

        "port": 5001

    }

}

{

    "service": {

        "id": "count2",

        "name": "Count",

        "tags": ["dev"],

        "address": "localhost",

        "port": 5002

    }

}

以第一个为例，注册一个服务id为count1，服务名称为Count，和之前配置中使用的相同，还有地址和端口。
使用 Ctrl+C 关闭正在运行的consul，然后输入 consul agent -dev -config-dir=C:/consul_1.0.7/consul.d 其中 C:/consul_1.0.7/consul.d 是本机的配置文件路径。
可以看到如下输出

==> Starting Consul agent...

==> Consul agent running!

           Version: 'v1.0.7'

           Node ID: '91af5002-a1d6-409e-e36b-f7a081f84d24'

         Node name: 'Weidaicheng-PC'

        Datacenter: 'dc1' (Segment: '<all>')

            Server: true (Bootstrap: false)

       Client Addr: [127.0.0.1] (HTTP: 8500, HTTPS: -1, DNS: 8600)

      Cluster Addr: 127.0.0.1 (LAN: 8301, WAN: 8302)

           Encrypt: Gossip: false, TLS-Outgoing: false, TLS-Incoming: false

==> Log data will now stream in as it occurs:

    2018/04/29 09:41:38 [DEBUG] agent: Using random ID "91af5002-a1d6-409e-e36b-f7a081f84d24" as node ID

    2018/04/29 09:41:38 [INFO] raft: Initial configuration (index=1): [{Suffrage:Voter ID:91af5002-a1d6-409e-e36b-f7a081f84d24 Address:127.0.0.1:8300}]

    2018/04/29 09:41:38 [INFO] raft: Node at 127.0.0.1:8300 [Follower] entering Follower state (Leader: "")

    2018/04/29 09:41:38 [INFO] serf: EventMemberJoin: Weidaicheng-PC.dc1 127.0.0.1

    2018/04/29 09:41:38 [INFO] serf: EventMemberJoin: Weidaicheng-PC 127.0.0.1

    2018/04/29 09:41:38 [INFO] consul: Adding LAN server Weidaicheng-PC (Addr: tcp/127.0.0.1:8300) (DC: dc1)

    2018/04/29 09:41:38 [INFO] consul: Handled member-join event for server "Weidaicheng-PC.dc1" in area "wan"

    2018/04/29 09:41:38 [INFO] agent: Started DNS server 127.0.0.1:8600 (udp)

    2018/04/29 09:41:38 [INFO] agent: Started DNS server 127.0.0.1:8600 (tcp)

    2018/04/29 09:41:38 [INFO] agent: Started HTTP server on 127.0.0.1:8500 (tcp)

    2018/04/29 09:41:38 [INFO] agent: started state syncer

    2018/04/29 09:41:38 [WARN] raft: Heartbeat timeout from "" reached, starting election

    2018/04/29 09:41:38 [INFO] raft: Node at 127.0.0.1:8300 [Candidate] entering Candidate state in term 2

    2018/04/29 09:41:38 [DEBUG] raft: Votes needed: 1

    2018/04/29 09:41:38 [DEBUG] raft: Vote granted from 91af5002-a1d6-409e-e36b-f7a081f84d24 in term 2. Tally: 1

    2018/04/29 09:41:38 [INFO] raft: Election won. Tally: 1

    2018/04/29 09:41:38 [INFO] raft: Node at 127.0.0.1:8300 [Leader] entering Leader state

    2018/04/29 09:41:38 [INFO] consul: cluster leadership acquired

    2018/04/29 09:41:38 [INFO] consul: New leader elected: Weidaicheng-PC

    2018/04/29 09:41:38 [DEBUG] consul: Skipping self join check for "Weidaicheng-PC" since the cluster is too small

    2018/04/29 09:41:38 [INFO] consul: member 'Weidaicheng-PC' joined, marking health alive

    2018/04/29 09:41:39 [DEBUG] agent: Skipping remote check "serfHealth" since it is managed automatically

    2018/04/29 09:41:39 [INFO] agent: Synced service "count1"

    2018/04/29 09:41:39 [INFO] agent: Synced service "count2"

    2018/04/29 09:41:39 [DEBUG] agent: Node info in sync

    2018/04/29 09:41:39 [DEBUG] agent: Service "count1" in sync

    2018/04/29 09:41:39 [DEBUG] agent: Service "count2" in sync

    2018/04/29 09:41:39 [DEBUG] agent: Node info in sync

    2018/04/29 09:41:39 [DEBUG] agent: Skipping remote check "serfHealth" since it is managed automatically

    2018/04/29 09:41:39 [DEBUG] agent: Service "count1" in sync

    2018/04/29 09:41:39 [DEBUG] agent: Service "count2" in sync

    2018/04/29 09:41:39 [DEBUG] agent: Node info in sync

在倒数第三行和倒数第二行可以看到count1和count2的两个服务注册成功，使用postman/浏览器请求一下http://localhost:8500/v1/catalog/service/count
可以看到注册的两个Count服务的信息

[

    {

        "ID": "91af5002-a1d6-409e-e36b-f7a081f84d24",

        "Node": "Weidaicheng-PC",

        "Address": "127.0.0.1",

        "Datacenter": "dc1",

        "TaggedAddresses": {

            "lan": "127.0.0.1",

            "wan": "127.0.0.1"

        },

        "NodeMeta": {

            "consul-network-segment": ""

        },

        "ServiceID": "count1",

        "ServiceName": "Count",

        "ServiceTags": [

            "dev"

        ],

        "ServiceAddress": "localhost",

        "ServiceMeta": {},

        "ServicePort": 5001,

        "ServiceEnableTagOverride": false,

        "CreateIndex": 6,

        "ModifyIndex": 6

    },

    {

        "ID": "91af5002-a1d6-409e-e36b-f7a081f84d24",

        "Node": "Weidaicheng-PC",

        "Address": "127.0.0.1",

        "Datacenter": "dc1",

        "TaggedAddresses": {

            "lan": "127.0.0.1",

            "wan": "127.0.0.1"

        },

        "NodeMeta": {

            "consul-network-segment": ""

        },

        "ServiceID": "count2",

        "ServiceName": "Count",

        "ServiceTags": [

            "dev"

        ],

        "ServiceAddress": "localhost",

        "ServiceMeta": {},

        "ServicePort": 5002,

        "ServiceEnableTagOverride": false,

        "CreateIndex": 7,

        "ModifyIndex": 7

    }

]

4、运行与结果查看

分别运行WebApiA、WebApiB、OcelotGatway三个项目，多次请求http://localhost:5000/Count，效果图如下

count.gif

可以看到，多次请求依次访问A、B、A......正是时间片轮询的负载均衡模式。

源码下载

完，下一篇介绍认证和授权

参考链接

https://blog.csdn.net/mr_seaturtle_/article/details/77618403
http://ocelot.readthedocs.io/en/latest/features/servicediscovery.html
https://www.consul.io/intro/getting-started/install.html

9人点赞

Ocelot

作者：Weidaicheng
链接：https://www.jianshu.com/p/05a1bf2545a0
来源：简书
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

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