This section describes how to run the NSCLDAQ event builder from the NSCLDAQ manager. Unlike the ReadoutGUI, where the event builder was often run in one-shot mode, we suggest running the Event builder in persitent mode under the manager.
This requires:
You create a program to start the event builder with its REST statistics plugin
You create program definitions for each data source.
You add these programs to a sequence that's executed by the BOOT transition
Create a program to shutdown the event builder (the sources will shutdown when their network peer exits).
Add the shutdown program to a sequence that's executed by the SHUTDOWN transition.
In the remainder of this section we will show how to execute the steps above.
Create a Program To Start The Event Builder. In fact, the event builder is a pipeline of programs. An Orderer which accepts fragments from data sources and outputs them totally time ordered to stdout, glom which glues together fragments into events and sends those events to its stdout, and finally stdintoring which drops the ring items glom built to a ringbuffer for distribution.
You will need to build a script that starts up this pipeline and define it as a program to the manager. The following sample script does that building events with a timestamp window of 250 ticks and dropping events into the ringbuffer fox_evb.
Example 4-2. An Event Builder Start Script
#!/bin/bash
TCLLIBPATH=$DAQTCLLIBS $DAQBIN/EVBRest \
| $DAQBIN/glom --dt 250 \
| $DAQBIN/stdintoring fox_evb
This script assumes the appropriate daqsetup.bash
script has been sourced. The first stage of the pipeline runs
the EVBRest
program which runs the orderer stage with a REST interface plugin.
The second stage of the pipeline run the glom program
described in
glom.
The --dt 250 option sets the
build window to 250 timestamp ticks. The final pipline stage takes the
output of glom and puts the ring items it produced into the ring named
fox_evb.
Use mg_cfgprogram to create a program that runs this script. Be sure to chmod the script so that it is executable by whomever will run the manager. In the remaining discussion, we'll assume this program was given the name startevb.
Specify the name of the program as startevb, specify the name of the script you created for the filename. Specify appropriate container, working directory and host values. Generally, event builders should be marked as Critical programs.
You should not normally require any options, parameters or environhment variables. These will be provided in your script.
Making a Program to Start a Data Source. This discussion assumes that the data comes from tcp://spdaq99/fox. We also assume the source ids are the default value of 0. Finally we assume that the program will run in an evironment with an appropriate daqsetup.bash sourced in.
In the program editor set the name to e.g. source99 Set the host to the name of the host in which you want the source to run. Choose an appropriate container definition if appropriate. Chose any working directory and mark the progrfam as Critical.
The following options should be specified:
--evbhostHost in which the event builder pipeline will run.
--evbnameSet this to the name of the user running the manager.
--infoSet this to a descriptive string. E.g: "spdaq99\ data"
There should be one of these for each source id the source will emit. The value should be the value of one of those ids. Note that most NSCLDAQ Readout programs only emit a single source id. A notable exception being the CAEN Digitizer readouts which emit a source id per digitizer.
--ringThe URI from which the data comes. In our example the value is tcp://spdaq99/fox
--expectbodyheadersNo value required. This indicates the data come from an 11.0 NSCLDAQ or later.
--oneshot=0Indicates the data source should not exit after an end of run condition.
For more information; see ringFragmentSource
Starting the Event Builder and Source(s) In a Boot Sequence. Now that you have your start programs, startevb to start the event builder pipeline and source99 to start the data source, using the sequence editor (mg_seqedit), If necessary create a sequence triggered by the BOOT transition. Add the startevb program to it and then add the source99 program with a pre-delay of 5 seconds so that the event builder has a chance to register and listen for connections on its REST service before ringFragmentSource tries to look up the service.
Making a Program to Shutdown The Event Builder. The EVBShutdown utility shuts down an event builder that is running a REST interface. Use mg_cfgprogram to add a program. Name it evbshutdown, run the prgram file $DAQBIN/EVBShutdown. Set the host, working directory and container appropriately.
The program parameters should be, in order, the host in which the event builder pipeline is running and the user running it. This is the host you specified the startevb program to run in. The user should be the user that will run the daq manager.
Note that shutting down the event builder pipeline will, eventually shutdown the data sources as they lose connection to the event builder.
Adding the Event Builder Shutdown to a SHUTDOWN Sequence . Using mg_seqedit if necessary, add a squence triggered on the SHUTDOWN transition. Edit that sequence and add the evbshutdown program to that sequence.