Nginx proxy_pass指令字符串插值 [英] Nginx proxy_pass directive string interpolation

问题描述

我正在Kubernetes上运行Nginx.

I'm running Nginx on Kubernetes.

当我使用以下proxy_pass指令时，它会按预期工作:

When I use the following proxy_pass directive it works as expected:

proxy_pass "http://service-1.default";

但是以下方法不起作用:

However the following does not work:

set $service "service-1";
proxy_pass "http://$service.default";

我收到一条错误消息，说no resolver defined to resolve service-1.default

I get an error saying no resolver defined to resolve service-1.default

据我所知proxy_pass正在接收完全相同的字符串，为什么它的行为有所不同?

As far as I can tell proxy_pass is receiving the exact same string so why is it behaving differently?

我需要使用一个变量，因为我正在使用正则表达式从URL动态获取服务名称.

I need to use a variable because I'm dynamically getting the service name from the URL using a regex.

推荐答案

我已经找到了原因和解决方案.

I've found the reason and a solution.

Nginx检测proxy_pass中是否正在使用变量(我不知道它是如何做到的).如果没有变量，它将在启动时解析主机名并缓存IP地址.如果存在变量，它将使用解析器(DNS服务器)在运行时查找IP.

Nginx detects if a variable is being used in proxy_pass (I don't know how it does that). If there is no variable it resolved the hostname at startup and caches the IP address. If there is a variable it uses a resolver (DNS server) to lookup the IP at runtime.

因此解决方案是像这样指定Kube DNS服务器:

So the solution is to specify the Kube DNS server like this:

resolver kube-dns.kube-system.svc.cluster.local valid=5s;
set $service "service-1";
proxy_pass "http://$service.default.svc.cluster.local";

请注意，必须使用服务的完整本地DNS名称，您可以通过运行nslookup service-1来获得该名称.

Note that the full local DNS name of the service must be used which you can get by running nslookup service-1.

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