kubernetes 上的 Nginx 代理

Question

我在 k8s 集群中有一个 nginx 部署，它代理我的 api/ 调用，如下所示：

server {
  listen 80;

  location / {
    root /usr/share/nginx/html;
    index index.html index.htm;
    try_files $uri $uri/ /index.html =404;
  }

  location /api {
    proxy_pass http://backend-dev/api;
  }
}

这在大多数情况下都有效，但是有时当 api pods 没有准备好时，nginx 会失败并出现错误：

nginx: [emerg] host not found in upstream "backend-dev" in /etc/nginx/conf.d/default.conf:12

在浏览互联网几个小时后，我发现 article 这几乎是同一个问题。我试过这个：

  location /api {
    set $upstreamName backend-dev;
    proxy_pass http://$upstreamName/api;
  }

现在nginx returns 502。还有这个：

  location /api {
    resolver 10.0.0.10 valid=10s;
    set $upstreamName backend-dev;
    proxy_pass http://$upstreamName/api;
  }

Nginx returns 503.

在 k8s 上修复它的正确方法是什么？

Answer 1

如果您的 API pods 没有准备好，Nginx 将无法将流量路由到它们。

来自 Kubernetes documentation:

The kubelet uses readiness probes to know when a Container is ready to start accepting traffic. A Pod is considered ready when all of its Containers are ready. One use of this signal is to control which Pods are used as backends for Services. When a Pod is not ready, it is removed from Service load balancers.

如果您没有使用活性或就绪探测，那么您的 pod 将被标记为 "ready"，即使容器内的应用程序运行尚未完成其启动过程并准备好接受交通.

可以找到关于 Pods 和 DNS 记录的相关部分 here

Because A records are not created for Pod names, hostname is required for the Pod’s A record to be created. A Pod with no hostname but with subdomain will only create the A record for the headless service (default-subdomain.my-namespace.svc.cluster-domain.example), pointing to the Pod’s IP address. Also, Pod needs to become ready in order to have a record unless publishNotReadyAddresses=True is set on the Service.

更新： 我建议使用 NGINX 作为 ingress controller.

当您使用 NGINX 作为入口控制器时，NGINX 服务会成功启动，并且每当 ingress rule is deployed, the NGINX configuration is reloaded on the fly.

这将帮助您避免 NGINX pod 重启。

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