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CHAPTER 2 WEB SERVER 7.0 ARCHITECTURE generate, create none none in none projectsprint code 39 Web Server ASP.NET Web Forms start stop worker primordial start stop watchdog start stop Web Server Processes The watchdog proce ss spawns the primordial process, which in turn spawns one or more worker processes. The worker process listens for HTTP requests on one or more ports and is responsible for processing requests received on those ports. The worker process is responsible for processing HTTP requests over secure and non-secure socket connections.

The sequence of creation of these processes (when you execute the startserv script to start your instance) is also shown in Figure 2.1 and is as follows: 1. Watchdog process 2.

Primordial process 3. Worker process The watchdog process and the primordial process provide a limited level of high availability within the server processes. If the worker process(es) crashes or terminates abnormally, the primordial process is responsible for restarting another worker process.

If the primordial process itself terminates abnormally, then the watchdog restarts another primordial process. On UNIX platforms, a Web Server instance has exactly one watchdog process, one primordial process, and one or more worker processes. On Windows platforms, each instance has exactly one watchdog process and one worker process.

There is no separate primordial process on Windows and each instance cannot start more than one worker process.. Note: A single pro none none cess could theoretically do the job of both the watchdog process and the primordial process. The reasons for their being separate processes (on UNIX platforms) are more historical than technical..

The primordial and worker processes are both named webservd. The name of the watchdog process is webservd-wdog..

2.1 SERVER PROCESSES On UNIX servers, t hese processes can be seen with the ps -ef command. The following example shows each of the processes for an instance running on Solaris:. # ps -ef grep http webserv d 14857 14856 0 Jan 22 33:12 webservd -d /sun/webserver7/ g -r /sun/webserver7 root 14856 14855 0 Jan 22 7:19 webservd -d /sun/webserver7/https-boulder. g -r /sun/webserver7 root 14855 1 0 Jan 22 0:04 webservd-wdog -d /sun/webserver7/https-boulder.example.

com/con g -r /sun/webse. Note: The ps comma none none nd provides important information about the process owner, the process ID, the parent process ID, the date the process was started, the daemon process that is running, and the parameters that were passed to the process. The rst column speci es the process owner which, in this case, is root for the watchdog and primordial processes. This is required if your Web Server is listening to a port less than 1024 (a privileged port on UNIX).

If the port is greater than 1024, the watchdog and primordial process can be a non-root user. The user for the child process owner is speci ed during the installation process. In this case the process owner is webservd, which is the default user.

The second column is the process ID of the running process, and the third column is the process ID of the parent process (or the process that started this process).. Looking at the ent ries from bottom to top, the following can be observed: Process 14855 is the watchdog process. It was started by the init process (which is indicated by a process ID of 1). Process 14856 is the primordial process.

It was started by the watchdog process. Process 14857 is the child process. It was started by the primordial process.

There is a parent/child relationship between the various processes. You can use the UNIX ptree command on the watchdog process to determine this relationship as follows:. # ptree 14855 CHAPTER 2 WEB SERVER 7.0 ARCHITECTURE 14855 webservd-wdo none none g -d /sun/webserver7/ g -r /sun/webse 14856 webservd -d /sun/webserver7/https-boulder. g -r /sun/webserver7 14857 webservd -d /sun/webserver7/https-boulder.example.

com/con g -r / sun/webserver7. 2.2 Web Server Architecture Web Server 7.0 is none none a multi-threaded, multi-process, highly scalable, and secure HTTP server. Of all the processes (watchdog, primordial, and worker) that are started for any Web Server instance, the worker process is the most interesting because it is the one that does the lion s share of work when it comes to processing HTTP requests.

Figure 2.2 shows some of the main components of the worker process..

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