To set keep=alive parameters in Apache2 Httpd, you need to pay attention to 3 directives:
The Keep-Alive extension to HTTP/1.0 and the persistent connection feature of HTTP/1.1 provide long-lived HTTP sessions which allow multiple requests to be sent over the same TCP connection. In some cases this has been shown to result in an almost 50% speedup in latency times for HTML documents with many images. To enable Keep-Alive connections, set
The number of seconds Apache will wait for a subsequent request before closing the connection. Once a request has been received, the timeout value specified by the
The
KeepAlive
KeepAliveTimeout
MaxKeepAliveRequests
KeepAlive Directive
| Description: | Enables HTTP persistent connections |
|---|---|
| Syntax: | KeepAlive On|Off |
| Default: | KeepAlive On |
| Context: | server config, virtual host |
| Status: | Core |
| Module: | core |
The Keep-Alive extension to HTTP/1.0 and the persistent connection feature of HTTP/1.1 provide long-lived HTTP sessions which allow multiple requests to be sent over the same TCP connection. In some cases this has been shown to result in an almost 50% speedup in latency times for HTML documents with many images. To enable Keep-Alive connections, set
KeepAlive On.
For HTTP/1.0 clients, Keep-Alive connections will only be used if they are specifically requested by a client. In addition, a Keep-Alive connection with an HTTP/1.0 client can only be used when the length of the content is known in advance. This implies that dynamic content such as CGI output, SSI pages, and server-generated directory listings will generally not use Keep-Alive connections to HTTP/1.0 clients. For HTTP/1.1 clients, persistent connections are the default unless otherwise specified. If the client requests it, chunked encoding will be used in order to send content of unknown length over persistent connections.
When a client uses a Keep-Alive connection it will be counted as a single "request" for the MaxRequestsPerChild directive, regardless of how many requests are sent using the connection.
KeepAliveTimeout Directive
| Description: | Amount of time the server will wait for subsequent requests on a persistent connection |
|---|---|
| Syntax: | KeepAliveTimeout seconds |
| Default: | KeepAliveTimeout 5 |
| Context: | server config, virtual host |
| Status: | Core |
| Module: | core |
The number of seconds Apache will wait for a subsequent request before closing the connection. Once a request has been received, the timeout value specified by the
Timeout directive applies.
Setting
KeepAliveTimeout to a high value may cause performance problems in heavily loaded servers. The higher the timeout, the more server processes will be kept occupied waiting on connections with idle clients.
In a name-based virtual host context, the value of the first defined virtual host (the default host) in a set of
NameVirtualHost will be used. The other values will be ignored.MaxKeepAliveRequests Directive
| Description: | Number of requests allowed on a persistent connection |
|---|---|
| Syntax: | MaxKeepAliveRequests number |
| Default: | MaxKeepAliveRequests 100 |
| Context: | server config, virtual host |
| Status: | Core |
| Module: | core |
The
MaxKeepAliveRequests directive limits the number of requests allowed per connection whenKeepAlive is on. If it is set to 0, unlimited requests will be allowed. We recommend that this setting be kept to a high value for maximum server performance.
For example:
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