三叶运维某日，组内后台开发找到我，问我们的 WEB 服务器超时设置是多少。他反馈的问题是，有一个 VLAN 切换任务 cgi 接口经常返回 504 网关超时错误，要我分析解决下。
我问了一下，得知这个请求遇到网络设备对象较多的时候，需要小半个小时才能完成，也就是要用到长连接才行。
老规矩，从开发那拿到接口地址，得到接入层服务器 IP，是一台 Haproxy 代理，看了一下 Haproxy 的超时设置：
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# 设置成功连接到一台服务器的最长等待时间，默认单位是毫秒，新版本的haproxy使用timeout connect替代，该参数向后兼容
contimeout 3600
# 设置连接客户端发送数据时的成功连接最长等待时间，默认单位是毫秒，新版本haproxy使用timeout client替代。该参数向后兼容
clitimeout 3600
# 设置服务器端回应客户度数据发送的最长等待时间，默认单位是毫秒，新版本haproxy使用timeout server替代。该参数向后兼容
srvtimeout 3600
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各种 1 小时超时，所以排除 Haproxy 的影响，继续往下看。
Haproxy 代理的是 2 台 Apache，也就是部署了 cgi 接口的服务器。第一时间查看了 httpd.conf 和 httpd-vhost.conf 中的配置，居然没找到超时设置。
于是，搜索了下相关教程，发现原来藏在了 httpd-default.conf 当中：
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#
# This configuration file reflects default settings for Apache HTTP Server.
#
# You may change these, but chances are that you may not need to.
#
#
# Timeout: The number of seconds before receives and sends time out.
#
Timeout 300
#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive On
#
# MaxKeepAliveRequests: The maximum number of requests to allow
# during a persistent connection. Set to 0 to allow an unlimited amount.
# We recommend you leave this number high, for maximum performance.
#
MaxKeepAliveRequests 100
#
# KeepAliveTimeout: Number of seconds to wait for the next request from the
# same client on the same connection.
#
KeepAliveTimeout 5
#
# UseCanonicalName: Determines how Apache constructs self-referencing
# URLs and the SERVER_NAME and SERVER_PORT variables.
# When set "Off", Apache will use the Hostname and Port supplied
# by the client. When set "On", Apache will use the value of the
# ServerName directive.
#
UseCanonicalName Off
#
# AccessFileName: The name of the file to look for in each directory
# for additional configuration directives. See also the AllowOverride
# directive.
#
AccessFileName .htaccess
#
# ServerTokens
# This directive configures what you return as the Server HTTP response
# Header. The default is 'Full' which sends information about the OS-Type
# and compiled in modules.
# Set to one of: Full | OS | Minor | Minimal | Major | Prod
# where Full conveys the most information, and Prod the least.
#
ServerTokens Full
#
# Optionally add a line containing the server version and virtual host
# name to server-generated pages (internal error documents, FTP directory
# listings, mod_status and mod_info output etc., but not CGI generated
# documents or custom error documents).
# Set to "EMail" to also include a mailto: link to the ServerAdmin.
# Set to one of: On | Off | EMail
#
ServerSignature On
#
# HostnameLookups: Log the names of clients or just their IP addresses
# e.g., www.apache.org (on) or 204.62.129.132 (off).
# The default is off because it'd be overall better for the net if people
# had to knowingly turn this feature on, since enabling it means that
# each client request will result in AT LEAST one lookup request to the
# nameserver.
#
HostnameLookups Off
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看了下，这些是 Apache 的默认配置，Apache 也没有 include 到 httpd.conf 当中。因此，编辑 httpd.conf，找到如下参数：
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#Include conf/extra/httpd-default.conf
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去掉注释，保存文件。然后再编辑 /usr/local/apache2/conf/extra/httpd-default.conf 文件，将 Timeout 的值修改为符合生产环境要求的 1800 秒，最后执行 Apache 平滑重启命令即可：
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/usr/local/apache2/bin/apachectl -k graceful
或者
/usr/local/apache2/bin/httpd -k graceful
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Ps：我之前一直以为只有 Nginx 有一个平滑 reload 命令，后面才知道 Apache、Haproxy 都支持平滑重启名称，这个非常棒！
重载之后，就不会出现 504 网关超时设置了。
