關于Consul(https://www.consul.io)是一個分布式，高可用,支持多數據中心的服務發現和配置共享的服務軟件,由 HashiCorp 公司用 Go 語言開發, 基于 Mozilla Public License 2.0 的協議進行開源。 在Consul的文檔上，Consul 支持Service Discovery, Health Checking, Key/Value Store, Multi DataCenter。運用Consul,可以在系統中build復雜的應用和服務的發現等。本文不是Consul的學習重點，關于更多Consul的學習，可參考：http://blog.csdn.net/column/details/consul.html

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閱讀本博客的前提是對Consul中數據中心，節點，服務，健康檢查等名詞，一些基本的consul命令，Consul UI的使用有一定的了解。

Ocelot對Consul支持是天生集成，在OcelotGateway項目中configuration.json配置就可以開啟consul+ocelot的使用，這套組合可以實現什么功能呢？

服務注冊，服務發現，API網關(ocelot固有，不作說明)，負載均衡，限流，熔錯告警，彈性和瞬態故障處理

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一、服務治理：服務注冊，服務發現

服務注冊和服務發現都是Consul自有的功能，可以通過Consul的http api完成注冊或發現，我寫了個NuGet庫ConsulSharp(https://github.com/axzxs2001/ConsulSharp)，可以在.net core下完成服務的注冊和發現，建議服務注冊做到一個統一的管理平臺里，為了測試方便，可以在Consul的配置文里先配置服務，每次Consul啟動時，自動注冊；關于服務發現，Ocelot自動可以完成，只需要在OcelotGateway項目中configuration.json進行配置就可以，接下來我們看看怎么配置。

首先下載Consul: https://www.consul.io/downloads.html，本項目是windows下進行測試

再下載Consul配置文件(這個配置文件是適合本例Demo的，可根據具體給你個況調整)https://github.com/axzxs2001/Asp.NetCoreExperiment/tree/master/Asp.NetCoreExperiment/ConsulOcelot/consul

conf文件夾：consul存放配置文件

dist文件夾：consul UI，一個小的consul信息展示門戶

data文件夾：consul啟動后存放consul的生成的數據和文件，在運行consul前可以清空此文件夾

Consul的配置文件如下：

{"encrypt": "7TnJPB4lKtjEcCWWjN6jSA==","services": [{"id": "API001","name": "API001","tags": [ "API001" ],"address": "192.168.1.99","port": 5001,"checks": [{"id": "API001_Check","name": "API001_Check","http": "http://192.168.1.99:5001/health","interval": "10s","tls_skip_verify": false,"method": "GET","timeout": "1s"}]},{"id": "API002","name": "API002","tags": [ "API002" ],"address": "192.168.1.99","port": 5002,"checks": [{"id": "API002_Check","name": "API002_Check","http": "http://192.168.1.99:5002/health","interval": "10s","tls_skip_verify": false,"method": "GET","timeout": "1s"}]}]}

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兩個服務API001和API002，跟著兩個健康檢查API001_Check和API002_Check

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基于consul服務的配置，現在創建三個asp.net core web api項目

OcelotGateway，網關項目，端口5000；API001業務API項目，端口5001；業務API項目，API002端口5002，代碼參見https://github.com/axzxs2001/Asp.NetCoreExperiment/tree/master/Asp.NetCoreExperiment/ConsulOcelot

OcelotGateway實現引入Ocelot網關，API001,API002實現健康檢查的兩個get請求。

測試服務注冊和發現：

1、 啟動consul

consul agent -server -datacenter=dc1 -bootstrap -data-dir ./data -config-file ./conf -ui-dir ./dist -node=n1 -bind 本機IP -client=0.0.0.0

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再啟動一個consul，查看狀態，命令：consul operator raft list-peers

結果：

Node? ID??????????????????????????????????? Address??????????? State?? Voter? RaftProtocol

n1??? dad74de2-173d-1c1e-add0-975a243b59eb? 192.168.1.99:8300? leader? true?? 3

用Consul UI查看

services:

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nodes:

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可以看到API001和API002服務，并且健康檢查都是正常的。

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2、 配置Ocelot網關

configuration.json文件如下(關于ocelot配置文件，詳見http://ocelot.readthedocs.io/en/latest/features/configuration.html)：

{"ReRoutes": [{"DownstreamPathTemplate": "/api/values","DownstreamScheme": "http","DownstreamHostAndPorts": [{"Host": "localhost","Port": 5001}],"UpstreamPathTemplate": "/api001/values","UpstreamHttpMethod": [ "Get" ],"ServiceName": "API001","LoadBalancer": "RoundRobin","UseServiceDiscovery": true,"ReRouteIsCaseSensitive": false,"QoSOptions": {"ExceptionsAllowedBeforeBreaking": 3,"DurationOfBreak": 10,"TimeoutValue": 5000},"HttpHandlerOptions": {"AllowAutoRedirect": false,"UseCookieContainer": false,"UseTracing": false},"AuthenticationOptions": {"AuthenticationProviderKey": "","AllowedScopes": []},"RateLimitOptions": {"ClientWhitelist": [ "admin" ],"EnableRateLimiting": true,"Period": "1m","PeriodTimespan": 15,"Limit": 5}},{"DownstreamPathTemplate": "/notice","DownstreamScheme": "http","DownstreamHostAndPorts": [{"Host": "localhost","Port": 5001}],"UpstreamPathTemplate": "/notice","UpstreamHttpMethod": [ "Post" ],     "ReRouteIsCaseSensitive": false,"QoSOptions": {"ExceptionsAllowedBeforeBreaking": 3,"DurationOfBreak": 10,"TimeoutValue": 5000},"HttpHandlerOptions": {"AllowAutoRedirect": false,"UseCookieContainer": false,"UseTracing": false},"AuthenticationOptions": {"AuthenticationProviderKey": "","AllowedScopes": []}   },{"DownstreamPathTemplate": "/api/values","DownstreamScheme": "http","DownstreamHostAndPorts": [{"Host": "localhost","Port": 5002}],"UpstreamPathTemplate": "/API002/values","UpstreamHttpMethod": [ "Get" ],"QoSOptions": {"ExceptionsAllowedBeforeBreaking": 3,"DurationOfBreak": 10,"TimeoutValue": 5000},"ServiceName": "API002","LoadBalancer": "RoundRobin","UseServiceDiscovery": true,"HttpHandlerOptions": {"AllowAutoRedirect": false,"UseCookieContainer": false},"AuthenticationOptions": {"AuthenticationProviderKey": "","AllowedScopes": []},"RateLimitOptions": {"ClientWhitelist": [ "user" ],"EnableRateLimiting": true,"Period": "1m","PeriodTimespan": 15,"Limit": 5}}],"GlobalConfiguration": {"ServiceDiscoveryProvider": {"Host": "localhost","Port": 8500},"RateLimitOptions": {"ClientIdHeader": "client_id","QuotaExceededMessage": "Too Many Requests!!!","DisableRateLimitHeaders": false}}}

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啟動OcelotGateway，API001，API002項目，通過http://localhost:5000/api001/values，和http://localhost:5000/api002/values訪問；因為Ocelot配置了Consul的服務治理，所以可以通過配置的服務名稱和GlobalConfiguratin的Consul http api接口查找到對應服務的地址，進行訪問，這些都是Ocelot幫我們做，這點很容易證明，可以修改Consul配置文件中服務的address為錯誤IP，就會發現通過5000端口訪問不成功。

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二、負載均衡

負載均衡需要啟動多個API001和API002，才能進行測試，所以發布API001和API002項目，并復制到一個與192.168.1.99在一個局域網的電腦中，同時把Consul和它的配置，UI文件也復制到這臺電腦上，網關項目OcelotGateway不需要，假設另外一臺電腦為192.168.1.126

首先修改Consul的配置文件如下

{"encrypt": "7TnJPB4lKtjEcCWWjN6jSA==","services": [{"id": "API001","name": "API001","tags": [ "API001" ],"address": "192.168.1.126","port": 5001,"checks": [{"id": "API001_Check","name": "API001_Check","http": "http://192.168.1.126:5001/health","interval": "10s","tls_skip_verify": false,"method": "GET","timeout": "1s"}]},{"id": "API002","name": "API002","tags": [ "API002" ],"address": "192.168.1.126","port": 5002,"checks": [{"id": "API002_Check","name": "API002_Check","http": "http://192.168.1.126:5002/health","interval": "10s","tls_skip_verify": false,"method": "GET","timeout": "1s"}]}]}

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在192.168.1.126下啟動API001，API002項目

啟動consul

consul agent -server -datacenter=dc1 -data-dir ./data -config-file ./conf -ui-dir ./dist -node=n2 -bind 192.168.1.126

同樣，在192.168.1.126下用Consul UI查看各服務是否正常

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在192.168.1.99下，把192.168.1.126加到集群中，命令如下

consul join 192.168.1.126

注意，consul集群中，consul配置文件中的encrypt，一定要相同，否則無法放加入同一個集群

用consul operator raft list-peers查看狀態，會發現n1,n2在一個集群中了

Node? ID??????????????????? ????????????????Address???????????? State???? Voter? RaftProtocol

n1??? dad74de2-173d-1c1e-add0-975a243b59eb? 192.168.1.99:8300?? leader??? true?? 3

n2??? efe954ce-9840-5c66-fa80-b9022167d782? 192.168.1.126:8300? follower? true?? 3

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些時在瀏覽器中多次訪問view-source:http://localhost:5000/api001/values或view-source:http://localhost:5000/api002/values，會發現返回的內容是交替出現的，因為只有兩個相同的API在集群中，這樣就實現了負載均衡。

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三、限流

限流是通過configuration.json配置完成的，具體值詳見http://ocelot.readthedocs.io/en/latest/features/ratelimiting.html

每個要限流Route中

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    "RateLimitOptions": {"ClientWhitelist": [ "admin" ],"EnableRateLimiting": true,"Period": "1m","PeriodTimespan": 15,"Limit": 5}

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GlobalConfiguration中"RateLimitOptions": {"ClientIdHeader": "client_id","QuotaExceededMessage": "too more request","DisableRateLimitHeaders": false}

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需要說明的是如果配置ClientWithelist白名單，需要在訪問api的客戶端添加一個Header項目，key為client_id，值為admin，此客戶端就不受限流控制

為了測試限流創建 TestClient控制臺程序進行測試，交果如下圖，在一分鐘內，用adminclinet訪問API001超過五次也可以，訪問API002，只能五次

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四、熔錯告警

熔斷保護在Consul中和Ocelot中都有實現，意義當一個服務不正常時，首先不影響正常使用(因為服務作了集群，可以把請求轉到別的服務器上)，二是發生問題，應該用所告警。Ocelot負載均衡可以自動發現服務出問題(Consul有健檢查)，并停止對異常服務請求；告警是通過Consul配置文件實現的，關于watches參看https://www.consul.io/docs/agent/watches.html

{"watches": [{"type": "checks","handler_type": "http","state": "critical","http_handler_config": {"path": "http://192.168.1.99:5000/notice","method": "POST","timeout": "10s","header": { "Authorization": [ "token" ] }}}]}

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在consul啟動時，會加載conf下的所有json文件，因為是json內容是watches節點，consul會作特定處理。

同時http://192.168.1.99:5000/notice映射的http://localhost:5001/notice中作了一個發郵件的操作，把發生異常的服務信息發送給對應郵箱，這里注意，測試時，不要關了API001測試，因為發郵件的功能在這個項目里，可以關掉API002測試，真實環境中，這塊肯定是獨立項目處理，并且采用集群的，效果如下：

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關掉192.168.1.99下的API2，作業報警郵件會提示準確的檢查錯誤和服務名稱。

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五、彈性和瞬態故障處理

彈性和瞬態故障處理，是Ocelot內置的功能，在網關轉發每個請求時，會用Polly(https://github.com/App-vNext/Polly)處理，設置詳見http://ocelot.readthedocs.io/en/latest/features/qualityofservice.html，開發上不作任何處理。

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轉載于:https://www.cnblogs.com/axzxs2001/p/8487521.html

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