您如何使用Azure API管理策略来负载均衡对后端服务的调用?

问题描述

如何使用策略来平衡对一对后端服务的呼叫负载? (在这种情况下，是在不同区域的一对Logic App)

How can you use policy to load balance calls to a pair of backend services? (in this case a pair of Logic Apps in different regions)

我已阅读 API管理策略并可以在控制流，但我不知道如何(a)测试后端服务是否可用，然后(b)如果主服务不可用，则将调用更改为备份服务

I've read through the API Management policies and can see something around the control flow but I can't work out how to (a) test the back-end service is available, and then (b) change the call to the backup service if the primary is unavailable

<backend>  
     <forward-request/>  
</backend> 

推荐答案

实现此目标的另一种方法可能是您可以使用重试策略，并带有设置后端服务或发送请求

One more way to achieve this could be that you can use the retry policy with set backend service or send-request

类似

<backend>
    <retry condition="@(context.Response.StatusCode == 400 || context.Response.StatusCode >= 500)" count="10" interval="10" max-interval="100" delta="10" first-fast-retry="false">
        <choose>
            <when condition="@(context.Response != null && (context.Response.StatusCode == 400 || context.Response.StatusCode >= 500)">
                <set-backend-service base-url="http://echoapibackup.cloudapp.net/api" />
            </when>
            <otherwise>
                <set-backend-service base-url="http://echoapi.cloudapp.net/api" />
            </otherwise>
        </choose>
        <forward-request />
    </retry>
</backend>

如果您的主后端返回错误，则会继续在您的备份后端上重试.

This will in case your primary backend returns an error, will keep retrying on your backup backend.

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