GCP HTTP负载平衡中的一些502错误 [英] Some 502 errors in GCP HTTP Load Balancing
问题描述
对于某些请求，我们的负载平衡器返回502错误.这仅占请求总数的很小一部分，我们每小时大约有36000个请求，每小时大约有40个错误，因此只有0.01％的请求返回错误.
Our load balancer is returning 502 errors for some requests. It is just a very low percentage of the total requests, we have around 36000 request per hour and about 40 errors per hour, so just a 0,01% of the requests returns an error.
发生错误时实例是正常的，并且我们已将此转发规则添加到负载均衡器的防火墙中: 130.211.0.0/22 tcp:1-5000应用于所有目标
The instances are healthy when the error occurs and we have added this forwarding rule to the firewall for the load balancer: 130.211.0.0/22 tcp:1-5000 Apply to all targets
这不是一个很严重的问题，因为应用程序可以容忍此类错误，但是我想知道为什么会给出这些错误.
It is not a very serious problem because the application tolerates such errors, but I would like to know why they are given.
任何帮助将不胜枚举.
推荐答案
似乎没有简单的解决方案.
It seems that there are no an easy solution for this.
As Mike Fotinakis explains in this blog (thank you for this info JasonG :)):
事实证明，Google Cloud HTTP(S)负载平衡器与NGINX的默认保持活动超时时间为65秒之间存在竞争.在负载均衡器尝试将连接重新用于另一个HTTP请求的同时，可能会达到NGINX超时，这会断开连接并导致负载均衡器产生502 Bad Gateway响应.
It turns out that there is a race condition between the Google Cloud HTTP(S) Load Balancer and NGINX’s default keep-alive timeout of 65 seconds. The NGINX timeout might be reached at the same time the load balancer tries to re-use the connection for another HTTP request, which breaks the connection and results in a 502 Bad Gateway response from the load balancer.
在我的情况下，我将Apache与mpm_prefork模块一起使用.提出的解决方案是将连接的保活超时增加到650s，但这是不可能的，因为每个连接都会打开一个新进程(这样会浪费大量资源).
In my case I'm using Apache with the mpm_prefork module. The solution proposed is to increase the connection keepalive timeout to 650s, but this is not possible because each connection opens one new process (so this would represent a great waste of resources).
更新:
似乎在官方负载均衡器文档页面上有一些有关此问题的新文档(搜索超时和重试"):
UPDATE:
It seems that there are some new documentation about this problem on the official load balancer documentation page (search for "Timeouts and retries"): https://cloud.google.com/compute/docs/load-balancing/http/
在两种情况下(Apache和Nginx)，他们都建议将KeepAliveTimeout值设置为620.
They recommend to set the KeepAliveTimeout value to 620 in both cases (Apache and Nginx).
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