最近我遇到了Apache的新麻烦。我们有一个运行在
上的Flask（1.0.2）中的Python（3.5）编写的应用程序$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.2 LTS
Release: 16.04
Codename: xenial
我们在ELB（AWS Elasict Loadbalancer）后面有两台服务器，然后它们突然（在该配置上运行了三个月以上）开始出现故障。我发现来自ELB的警报和用于监视的外部工具。我们突然开始收到E408（超时）和E503（服务不可用）。
我开始挖掘可能是什么原因， 在apache日志中，我发现很多这样的消息（似乎就在失败之前）：
[Mon Jun 25 22:27:04.613967 2018] [wsgi:error] [pid 1275:tid 139684390848256] (70008)Partial results are valid but processing is incomplete: [client 1.2.3.4:2819] mod_wsgi (pid=1275): Unable to get bucket brigade for request., referer: https://xx.xx.xx/
我还查询了syslog并看到了这个：
Jun 25 22:13:25 my_hostname systemd[1]: Created slice User Slice of ubuntu.
Jun 25 22:13:25 my_hostname systemd[1]: Starting User Manager for UID 1000...
Jun 25 22:13:25 my_hostname systemd[1]: Started Session 1424 of user ubuntu.
Jun 25 22:13:25 my_hostname systemd[6239]: Reached target Sockets.
Jun 25 22:13:25 my_hostname systemd[6239]: Reached target Timers.
Jun 25 22:13:25 my_hostname systemd[6239]: Reached target Paths.
Jun 25 22:13:25 my_hostname systemd[6239]: Reached target Basic System.
Jun 25 22:13:25 my_hostname systemd[6239]: Reached target Default.
Jun 25 22:13:25 my_hostname systemd[6239]: Startup finished in 8ms.
Jun 25 22:13:25 my_hostname systemd[1]: Started User Manager for UID 1000.
Jun 25 22:14:47 my_hostname systemd[1]: Stopping LSB: Apache2 web server...
Jun 25 22:14:47 my_hostname apache2[6624]: * Stopping Apache httpd web server apache2
Jun 25 22:14:59 my_hostname apache2[6624]: *
Jun 25 22:14:59 my_hostname systemd[1]: Stopped LSB: Apache2 web server.
Jun 25 22:14:59 my_hostname systemd[1]: Starting LSB: Apache2 web server...
Jun 25 22:14:59 my_hostname apache2[6660]: * Starting Apache httpd web server apache2
Jun 25 22:14:59 my_hostname apache2[6660]: AH00557: apache2: apr_sockaddr_info_get() failed for my_hostname
Jun 25 22:14:59 my_hostname apache2[6660]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1. Set the 'ServerName' directive globally to suppress this message
Jun 25 22:15:00 my_hostname apache2[6660]: *
Jun 25 22:15:00 my_hostname systemd[1]: Started LSB: Apache2 web server.
有趣的是，两个服务器（几乎完全相同）同时发生故障（由于部署了新版本，因此它们大约在同一时间重新启动，并且两者的流量可能几乎相同，因为它们位于一个负载均衡器的后面）。 / p>
已经尝试发现类似问题，但到目前为止还没有运气。
还有一件有趣的事情，我在日志中发现了几条这样的消息：
[Mon Jun 25 22:27:04.657763 2018] [wsgi:error] [pid 1274:tid 139684507617024] [remote 172.31.12.149:720] mod_wsgi (pid=1274): Exception occurred processing WSGI script '/home/ubuntu/my_app/app.wsgi'.
[Mon Jun 25 22:27:04.658503 2018] [wsgi:error] [pid 1274:tid 139684482414336] [remote 172.31.12.149:62417] mod_wsgi (pid=1274): Exception occurred processing WSGI script '/home/ubuntu/my_app/app.wsgi'.
[Mon Jun 25 22:27:04.658528 2018] [wsgi:error] [pid 1274:tid 139684532819712] [remote 172.31.12.149:52139] mod_wsgi (pid=1274): Exception occurred processing WSGI script '/home/ubuntu/my_app/app.wsgi'.
[Mon Jun 25 22:27:04.658584 2018] [wsgi:error] [pid 1274:tid 139684482414336] [remote 172.31.12.149:62417] OSError: failed to write data
[Mon Jun 25 22:27:04.658818 2018] [wsgi:error] [pid 1274:tid 139684516017920] [remote 172.31.12.149:208] OSError: failed to write data
[Mon Jun 25 22:27:04.659999 2018] [wsgi:error] [pid 1274:tid 139684532819712] [remote 172.31.12.149:52139] OSError: failed to write data
[Mon Jun 25 22:27:04.660411 2018] [wsgi:error] [pid 1274:tid 139684507617024] [remote 172.31.12.149:720] OSError: failed to write data
不确定是否可以关联，但是我确定我们会在请求完成之前取消很多请求（出于原因）。
此外，我们在Ubuntu + Flask（以及更多可能是相同的设置）上运行了多年，我们从来没有遇到过这样的问题。
真的很感谢任何想法，谢谢！