Monitor program
Section 2: the use of the "monitor" program to communicate and, to some extent, control the uDST daemon
Although the user can monitor and control the production via the control/status field (column 8) of each fill's entry in the fill.conf file, an additional program, called "monitor", allows the user to view and, to some extent, control with the operation of the daemon. Just like the daemon, this program is executed by setting the current working directory to the /bin subdirectory of a production and then entering the "monitor" command. The monitor program will then open up pipes, called UdstIn and UdstOut, to communicate with the daemon and then waits for one-letter, case-sensitive user commands from the keyboard. When the monitor receives a command, it communicates with the daemon accordingly and then displays the output information for the command. Presently, the following commands are supported:
| f | - |
display and modify the current production status of fills When the monitor receives this command, it will request all the fill information (basically the contents of the fill.conf file) from the uDST production daemon and then display this information on the screen. In this display, the monitor highlights one fill in reverse video to indicate which the one which is currently selected for modification. The user can use the "up-arrow" and "down-arrow" keys to scroll the display by one line and the ">" and "<" keys to scroll the display by one page. To modify the production status of the fill, (i.e. put a fill into production, delete a production, etc.), the user first scrolls through the list of fills until the desired fill is the one selected for modification and then press the [RETURN] key to initiate the modification. At this time, the monitor pauses the uDST production daemon (so that only one program is modifying the fill information at a time) and highlights only the control/status field (column 8) of the selected fill. The user can now use the "up-arrow" and "down-arrow" key to scroll through the available control options. The user can select a new control option by pressing the [RETURN] key or abort the change by pressing the Q key. If the user selects a new control/status option, the monitor firsts validates the desired transition because it is not legal to switch between certain control/status states (e.g., a fill cannot be changed from done to go directly). If the transition is illegal, the monitor program retains the old state without comment, in effect, ignoring what the user selected. After completing this check, the monitor program transmits the resulting state for this fill to the uDST production daemon, resumes the uDST production daemon, and updates the fill display accordingly. If the user decides to make no change, the monitor program simply release the uDST production daemon from its paused state. | ||
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| p | - | look at the number of processes in production and the maximum number of process which can be in production | ||
| P | - | change the maximum number of allowed processes. The monitor program will prompt the user for the new value for this maximum. This number will be communicated to the daemon and become the new maximum number of production processes which the daemon is allowed to run at one time. If this setting is less than the current number of processes, the daemon will reduce the number of processes by not initiating a new process when a current process completes. | ||
| d | - |
look at and modify the current status of disks When the monitor program receives this command, it requests the production status for disk (basically the contents of the disk.conf file) from the uDST production daemon and then displays this information on the screen. In this display, the monitor highlights one fill in reverse video to indicate which the one which is currently selected for modification. The user can use the "up-arrow" and "down-arrow" keys to scroll the display by one line and the ">" and "<" keys to scroll the display by one page. To modify the production status of the disk, (i.e. increase or decrease the number of productions which can simultaneously be done on given disk), the user first scrolls through the list of disks until the desired disk is the one selected for modification and then press the c key to initiate a change. At this time, the monitor pauses the uDST production daemon (so that only one program is modifying the fill information at a time) and, on the bottom of the screen, asks for the new maximum number of processes for the disk. After the user enters this quantity, the monitor transmits it to the uDST resumes the uDST production daemon, and updates the disk display accordingly. | ||
| a | - |
request the daemon to initiate a production pass When the monitor receives this command, it ask the daemon to try to initiate a production pass. If the process limit has not been reached, there is an available disk, and there is a fill pending some action, the daemon will start a process to perform this action on the fill. Otherwise, this command will have no effect.
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| h | - | brief help information for each command |