Using Stager/ReadoutGUI

Using Stager/ReadoutGUI

The stager consists of two components:

1. The stager itself
2. A Graphical User Interface (GUI) front end to your readout program.

Stager and its associated graphical user interface (GUI) is responsible for gathering information about your run and using it to decide when and where to spool event data from your staging area out to tape. Staging is done to free up space for additional event data.

Staging produces a Unix tar tape that contains your event data and any other ancillary data you want to associate with each run. Once staged to tape, the event data associated with the staged runs are deleted.

The stager can keep a specified set of files around after the stage pass.

ReadoutGUI runs your readout program on the specified (possibly remote) spdaq system. It provides a graphical front end that allows you to control your experiment.

Features include:

• Remote control over readout software through an easy to use GUI.
• Support to control the title and run number.
• Support for fixed time runs.
• Catches Readout abnormal exits and lets you know about this, and supports restarting the program.
• Safe against builds on top of running software.

Stager

The first time you run stager, you will be interviewed for information about your experimental configuration. The figure below shows the tape host selection dialog:

In the "Host with tapedrive:" text entry, type the name of the computer whose tape drive you will use. Normally, if you are using event1 or event2, you should use daq1. Use daq2 for any other stage area. If you are in doubt about which host to use, ask a member of the computer group support staff.

In the "Password for user" text entry type in your login password for that system. The password will not be readably echoed.

The figure below shows the tape selection dialog.

In this dialog select the actual tape drive to which you will put data and select the capacity of the tape cartridge in the mode in which you will run that drive. In general on Unix, there is no way to programatically determine the amount of data that fits on a tape, the selection you make is used to determine the size of the tape.

The figure below shows the readout program selection dialog:

Type the name of the computer that is attached to your experimental hardware in the top entry. Type the full path to your readout program in the bottom entry line or click the "browse..." button to browse the filesystem for your program.

The figure below shows the stage policy dialog:

Normally, you can leave this alone. The default policy is to start a stage pass when the used space on the stage disk goes above some percentage of total size of the stage area. The alternative is to stage when the total size of the data in your event area crosses a threshold.

If you have already run the stager you will not necessarily have to answer all the questions in this interview again. The stager remembers your answers from the last time it was run. It prompts you to accept them or reject with the dialog box shown below.

If you reject the saved settings, you will have to go through the interview process again. If you accept them, Stager will startup with your saved values.

Once the stager knows what to do, it displays its graphical user interface:

• The two scale bars at the top of the interface allow you to set the threshold at which staging occurs, and to view what the current usage is relative to this threshold. In the screen shot above, Staging will occur when the disk space used on the stage area goes above 80% of the capacity of the area. The current usage is 61% of capacity.
• The Exit button exits the stager after giving an "Are you sure" prompt.
• The Stage Now... button forces the data to be staged now. This is useful at the end of an experiment, to force the last runs to stage totape.
• The Retain... button allows you to select runs to be retained after a stage pass. The event data for retained runs are not removed from the staging area after stage passes.
• The large central region of the dialog shows messages emitted during the stage passes.
• The change tape button indicates that you are changing tapes and forces Stager's tape usage to 0. Always indicate you are changing tapes by clicking this button, otherwise the Stager will not know that you have done so.
• The status bar above the button shows what's been done with the current tape.

ReadoutGUI

ReadoutGui is started by the stager. The ReadouGui starts up the selected readout program and runs it on the specified spdaq system. The GUI provides a graphical front end to the limited command set of the Readout program.

The Readout GUI has the following elements:

• The File menu allows you to select a new readout program or restart an existing program. On the production readout software you can also source TCL Scripts into the readout program.
• The Scalers menu allows you to set scaler readout parameters.
• The topmost text status line displays the path of the program being run and the name of the host onwhich it's being run.
• The title entry allows you to set the title, when the run is halted.
• The run number entry allows you to set the run number when the run is halted.
• The record events check box allows you to request that the next run be put to tape.
• The begin and pause buttons allow you to control the run. When the run is active, the begin button is relabeled End. When the run is paused, the pause button is relabeled Resume.
• The timed run check box indicates the next run will be a fixed length run for the amount of time specified in the Run Duration entry.
• The Elapsed time shows how long the current run has been active.
• The large text area below the controls shows messages emitted by the Readout program. Both stdout and stderr are captured here.
• The status line at the very bottom shows how much data has gone to disk for the current run if the run is recording data.

Using Stager/ReadoutGUI