Sun Microsystems 820433510 manual Configuring the Http Service 151

HTTP Listeners

However, if an HTTP listener uses the 0.0.0.0 IP address, which listens on all IP addresses on a port, you cannot create HTTP listeners for additional IP addresses that listen on the same port for a specific IP address. For example, if an HTTP listener uses 0.0.0.0:8080 (all IP addresses on port 8080), another HTTP listener cannot use 1.2.3.4:8080.

Because the system running the Enterprise Server typically has access to only one IP address, HTTP listeners typically use the 0.0.0.0 IP address and different port numbers, with each port number serving a different purpose. If the system does have access to more than one IP address, each address can serve a different purpose.

By default, when the Enterprise Server starts, it has the following HTTP listeners:

■Two HTTP listeners named http-listener-1 and http-listener-2, associated with the virtual server named server. The listener named http-listener-1 does not have security enabled; http-listener-2 has security enabled.

■An HTTP listener named admin-listener, associated with the virtual server named __asadmin. This listener hasdoes not have security enabled.

All these listeners use the IP address 0.0.0.0 and the port numbers specified as the HTTP server port numbers during installation of the Enterprise Server. If the Enterprise Server uses the default port number values, http-listener-1 uses port 8080, http-listener-2 uses port 8181, and admin-listener uses port 48489.

Each HTTP listener has a default virtual server. The default virtual server is the server to which the HTTP listener routes all request URLs whose host component does not match any of the virtual servers that are associated with the HTTP listener (a virtual server is associated with an HTTP listener by listing the HTTP listener in its http-listeners attribute).

In addition, specify the number of acceptor threads in the HTTP listener. Acceptor threads are threads that wait for connections. The threads accept connections and put them in a queue, called the connection queue, where they are then picked up by worker threads. Configure enough acceptor threads so that there is always one available when a new request comes in, but few enough so that they do not provide too much of a burden on the system. In the Enterprise Server, there is no distinction between acceptor and request processing (worker) threads: each HTTP listener thread is responsible for accepting and processing requests. For this reason, the HTTP listeners in the Enterprise Server’s default configuration use 50 acceptor threads. The connection queue includes both the new connections just accepted by acceptor threads and persistent connections managed by the Keep-Alive connection management subsystem.

A set of request processing threads retrieves incoming HTTP requests from the connection queue and processes the requests. These threads parse the HTTP headers, select the appropriate virtual server, and run through the request processing engine to service the request. When there are no more requests to process, but the connection can be kept persistent (either by using HTTP/1.1 or sending a Connection: keep-alive header), the request processing thread assumes the connection to be idle and passes the connection to the Keep-Alive connection management subsystem.

Chapter 13 • Configuring the HTTP Service 151