The spatial servers, virtual servers, and ArcIMS services of ArcIMS are logically divided objects or concepts that depend on the existence of actually running ArcIMS processes on computers, 2 steps 7:
Figure 2 process of ArcIMS
The reason is that we have installed the ArcMap image extension, which will generate two other space server processes.
These six processes are divided into four types: Application Server, monitor, tasker, and spatial server. The following describes these four processes in detail:
2.3.1. Application Server process
The application server process is responsible for allocating external requests to maintain load balancing on the server system. It determines which service runs on which virtual server. Because it can monitor the status of the Space server objects on the virtual server, it can delegate requests to suitable space server objects for processing. If the number of requests received by ArcIMS exceeds the available space server, these requests will not be discarded, but will be stored in the Application Server sequence for submission and sending.
The Application Server saves the configuration information of the entire site through a configuration file named arcimssite. SEZ, which is used when the ArcIMS server is restarted. You can find it in the appserver folder in the installation directory of ArcIMS on Windows or $ aimshome/middleware/application_server on UNIX and Linux platforms. If an error occurs on the server, delete the file and restart the service. After the service is started, an arcimssite. SEZ file is generated again.
In addition, the default port occupied by application server processes is 5353.
2.3.2. Monitor listening process
The role of a listening process is to manage the space server process, including starting the space server process, keeping it running, and stopping the process.
When ArcIMS is started, the monitor process starts the space server process, and then monitors the other party in the background to maintain its normal state. At the same time, the application server process starts to communicate with the space server. Once the interaction process is interrupted, the application server process immediately sends a command to the listening process and restarts the process of the Space server.
2.3.3. Spatial server space server process
We have carefully understood the space server progress in 2.2, which is an aimsserver.exeProgram. A computer can have multiple space server processes to simultaneously process multiple types of map requests.
2.3.4. Tasker task process
We know that during MAP access to ArcIMS, The ArcIMS server will generate map image files on the server hardware. These files are stored in the output folder of ArcIMS management, if these files are not cleared regularly, long-term access will inevitably occupy limited hard disk space.
The Tasker process can monitor the status of these temporary files. If the interval between their generation time and the current time is greater than the specified time interval, the temporary files will be deleted.
How does the ArcIMS server complete the startup process? The application server process is started first. The following sequence is as follows:
The monitor process is registered to the application server process;
The application server process initializes and sends commands to the Monitor process to start one or more spatial server processes;
All spatial server processes are registered with the application server process;
Application Server initializes each spatial server process and enables each spatial server process to start one or more instances );
All instances are registered to the application server;
Application Server adds the ArcIMS service to each instance.
Knowledge: process and thread
Programs Written in different languages are just a collection of commands in the computer, and processes are actually running in the computer. Therefore, we usually define a process as a running program instance.
The process itself does not run. It is only the container of the thread [2] (thrend), and actually runs the thread contained in it. A single process may contain multiple threads. Each thread has its own set of CPU registers and stack space. Each process has at least one thread to executeCode. If the process does not exist, the system will automatically undo the process and its address space.
[1] http://zh.wikipedia.org/wiki/process
[2] http://zh.wikipedia.org/w/index.php? Title = % E5 % 9f % B7 % E8 % a1 % 8C % E7 % B7 % 92 & variant = ZH-CN