What httpd conf settings do I need to change to increase the max number of concurrent connections for Apache? NOTE: I turned off KeepAlive since this is mainly an API server.
#
# 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>
This question is related to
apache
change the MaxClients directive. it is now on 256.
Here's a detailed explanation about the calculation of MaxClients and MaxRequestsPerChild
ServerLimit 16
StartServers 2
MaxClients 200
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
First of all, whenever an apache is started, it will start 2 child processes which is determined by StartServers
parameter. Then each process will start 25 threads determined by ThreadsPerChild
parameter so this means 2 process can service only 50 concurrent connections/clients i.e. 25x2=50. Now if more concurrent users comes, then another child process will start, that can service another 25 users. But how many child processes can be started is controlled by ServerLimit
parameter, this means that in the configuration above, I can have 16 child processes in total, with each child process can handle 25 thread, in total handling 16x25=400 concurrent users. But if number defined in MaxClients
is less which is 200 here, then this means that after 8 child processes, no extra process will start since we have defined an upper cap of MaxClients
. This also means that if I set MaxClients
to 1000, after 16 child processes and 400 connections, no extra process will start and we cannot service more than 400 concurrent clients even if we have increase the MaxClient
parameter. In this case, we need to also increase ServerLimit
to 1000/25 i.e. MaxClients/ThreadsPerChild=40
So this is the optmized configuration to server 1000 clients
<IfModule mpm_worker_module>
ServerLimit 40
StartServers 2
MaxClients 1000
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>
Source: Stackoverflow.com