如何增加Apache的最大并发连接数？

Question

我需要更改哪些 httpd conf 设置才能增加 Apache 的最大并发连接数？注意：我关闭了 KeepAlive，因为这主要是一个 API 服务器。

#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive Off

#
# 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 15

##
## Server-Pool Size Regulation (MPM specific)
## 

# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# ServerLimit: maximum value for MaxClients for the lifetime of the server
# MaxClients: maximum number of server processes allowed to start
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule prefork.c>
StartServers       8
MinSpareServers    5
MaxSpareServers   20
ServerLimit      256
MaxClients       256
MaxRequestsPerChild  4000
</IfModule>

# worker MPM
# StartServers: initial number of server processes to start
# MaxClients: maximum number of simultaneous client connections
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule worker.c>
StartServers         2
MaxClients         150
MinSpareThreads     25
MaxSpareThreads     75 
ThreadsPerChild     25
MaxRequestsPerChild  0
</IfModule>

Answer 1

这里有关于MaxClients和MaxRequestsPerChild的计算的详细解释

http://web.archive.org/web/20160415001028/http://www.genericarticles.com/mediawiki/index.php?title=How_to_optimize_apache_web_server_for_maximum_concurrent_connections_or_increase_max_clients_in_apache

ServerLimit 16
StartServers 2
MaxClients 200
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25

首先，每当apache启动时，它都会启动2个子进程，这是由

StartServers

参数决定的。然后每个进程将启动由

ThreadsPerChild

参数确定的 25 个线程，因此这意味着 2 个进程只能服务 50 个并发连接/客户端，即 25x2=50。现在，如果出现更多并发用户，则会启动另一个子进程，该子进程可以为另外 25 个用户提供服务。但是可以启动多少个子进程是由

ServerLimit

参数控制的，这意味着在上面的配置中，我总共可以有16个子进程，每个子进程可以处理25个线程，总共可以处理16x25=400个并发用户。但是，如果

MaxClients

中定义的数量小于200，那么这意味着在8个子进程之后，不会启动额外的进程，因为我们已经定义了

MaxClients

的上限。这也意味着，如果我将

MaxClients

设置为 1000，则在 16 个子进程和 400 个连接之后，不会启动额外的进程，即使我们增加了

MaxClient

参数，我们也无法为超过 400 个并发客户端提供服务。在这种情况下，我们还需要将

ServerLimit

增加到 1000/25，即

MaxClients/ThreadsPerChild=40

所以这是服务 1000 个客户端的优化配置

<IfModule mpm_worker_module>
    ServerLimit          40
    StartServers          2
    MaxClients          1000
    MinSpareThreads      25
    MaxSpareThreads      75 
    ThreadsPerChild      25
    MaxRequestsPerChild   0
</IfModule>

Answer 2

更改 MaxClients 指令。默认值通常是 256。

Answer 3

对于 Ubuntu 上的默认 Apache/PHP 安装，请将

mpm_worker_module

替换为

mpm_prefork_module

，如下所示：

    <IfModule mpm_prefork_module>
            ServerLimit 16
            StartServers 2
            MaxClients 200
            MinSpareThreads 25
            MaxSpareThreads 75
            ThreadsPerChild 25
    </IfModule>

注意：如果您打算继续

mpm_worker_module

，您需要更改 PHP 多重处理模式。您可以按照此处描述的指南进行操作（未经测试）： https://askubuntu.com/a/1319874/496298