Web server plug-in connections
The web server plug-ins are used to establish and maintain persistent HTTP and HTTPS connections to application servers.
When the plug-in is ready to send a request to the application server, it first checks its connection pool for existing connections. If an existing connection is available the plug-in checks its connection status. If the status is still good, the plug-in uses that connection to send the request. If a connection does not exist, the plug-in creates one. If a connection exists but has been closed by the application server, the plug-in closes that connection and opens a new one.
After a connection is established between a plug-in and an application server, it will not be closed unless the application server closes it for one of the following reasons:
- If the Use Keep-Alive property is selected and the time limit specified on the Read timeout or Write timeout property for the HTTP inbound channel has expired.
- The maximum number of persistent requests which can be processed on an HTTP inbound channel has been exceeded. This number is set using the Maximum persistent requests property that is specified for the HTTP inbound channel.
- The Application Server is shutting down.
- The plug-in receives a new HTTP request and tries to reuse the existing connection.
- The number of httpd processes drop because the web server is not receiving any new HTTP requests. For the IBM® HTTP Server, the number of httpd processes that are kept alive depends on the value specified on the web server's MinSpareServers directive.
- The web server is stopped and all httpd processes are terminated, and their corresponding sockets are closed.