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Running DAQ Interface » History » Version 106

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John Freeman, 03/10/2015 05:23 PM


Getting help

If, after reading this document (in particular, the "Troubleshooting and FAQ" section) you run into issues, or have questions, please contact:

Logbook

Please document all changes, software updates, and operational activities to the ELog:

http://dbweb3.fnal.gov:8080/ECL/lbne_35t

Starting DAQInterface and Run Control

The DAQ software, consisting of RunControl, the configuration manager and DAQInterface (as well as the artdaq processes it controls) is designed to be run on lbne35t-gateway01.fnal.gov, using the lbnedaq account. If you need access to the account, please contact one of us.

The installed code is located at lbne35t-gateway01.fnal.gov:/data/lbnedaq/daqarea/lbnerc. To get started, login and first setup the environment:

ssh lbnedaq@lbne35t-gateway01.fnal.gov
cd /data/lbnedaq/daqarea
source fireup

This will take you into the /data/lbnedaq/daqarea/lbnerc directory. It's a good idea to check whether lbnecontrol (the RunControl application), DAQInterface (the component which intermediates between RunControl, the configuration manager, and the artdaq processes) and the configuration manager are already running; if they are, the instructions below won't work. Also worth noting is that as of 11/21/14, attempts to use multiple DAQs (implying multiple instances of RunControl, DAQInterface, etc.) has not been attempted and likely will not work. To check for RunControl and DAQInterface, you can try:

lbnecmd check

This will display the current state of DAQInterface and RunControl. The example below shows that both RunControl and DAQInterface are running, but the DAQ run is in the stopped state:

(env)[lbnedaq@lbne35t-gateway01 lbnerc]$ lbnecmd check
lbnecontrol: running
daqint@localhost:5770 (synchronous): stopped

If RunControl is running, and at some point DAQInterface was running but has since been killed:

lbnecontrol: running
daqint@localhost:5770 (synchronous): missing

(In this case, just restart DAQInterface -- how to do this is described shortly).

If RunControl is not running, you'll see something like:

(env)[lbnedaq@lbne35t-gateway01 lbnerc]$ lbnecmd check
check failed: '[Errno 111] Connection refused'.  Is lbnecontrol running?

To check whether the configuration manager is running, you can simply use Linux commands:

ps aux | grep -v grep | grep CfgMgrApp

This will either return info on CfgMgrApp (the actual name of the configuration manager process), or print nothing if it's not running. In fact, it's possible to use Linux commands to check the status of all three programs:

ps aux | grep -v grep | egrep -e lbnecontrol -e daqinterface -e CfgMgrApp

If you wish to kill any of these processes (described in the next section), the PID (process ID) to use is supplied as the second field in each row returned by the "ps aux" command.

Cleanup: killing RunControl, DAQInterface and the configuration manager

To begin using the DAQ, you'll want to kill off any existing RunControl and/or DAQInterface processes. With the process IDs obtained from the command described in the previous section, you can kill any pre-existing such processes. Keep in mind, of course, that if these processes are running, it might mean that someone else is using the DAQ, or that someone else who's done using it forgot to clean up. As the 9th and 10th fields of the row of variables "ps aux" returns concern how long the program has been running, you can use these values as well as your best judgement, then, before deciding these processes are not in active use and killing them. To kill them, again keeping in mind that the second field returned from "ps aux" is the process id (PID), use:

kill <PID>

If daqinterface is killed externally, then if it was in any state other than "stopped" at the time (and it likely was, otherwise a hard reset would likely have been avoidable), it's quite possible that it's left "orphaned" artdaq processes. If this is the case, you'll want to clean these up before trying to run the DAQ again, as they'll block the ports if they remain alive as "zombie" processes. Check the DAQInterface configuration file (defaults to lbnerc/docs/config.txt unless an alternate was supplied via the "-f" option to DAQInterface) to see which node the PMT (Process Management Tool) was running on, and check for it with
ps aux | grep -v grep | grep pmt.rb

Use this to get the process ID to kill it. Of course, also be aware that if artdaq processes were in communication with hardware when the orphaning occurred, killing them off might result in issues for the hardware, but the specifics of any hardware issues that may arise go beyond the scope of this document.

Starting RunControl

To start RunControl (after loading environment as above):

rm -f /tmp/lbnecontrol.pid  # (This should only be necessary if RunControl software wasn't stopped cleanly)
lbnecmd launch

Starting DAQInterface

To start DAQInterface (after loading environment as above), the basic command is:

daqinterface -n daqint -r 5570 -c localhost -H localhost -f <daqinterface file> &

Here, the "daqint" argument is arbitrary, and is the name you'll give the DAQInterface process in RunControl; the "5570" argument is the port off of which DAQInterface will run. The "-f <daqinterface file>" is optional; if left out, the lbnerc/docs/config.txt file will be used to configure DAQInterface, otherwise <daqinterface file> will be used. The DAQInterface configuration is not to be confused with run configurations handled by the configuration manager; see the section "Configuring DAQInterface" for more.

If multiple users with different terminals wish to check the DAQ output, it is recommended to try:

stdbuf -oL daqinterface -n daqint -r 5570 -c localhost -H localhost -f <daqinterface file> >>~/DI.log 2>&1 &

This will launch daqinterface in the background, with all messages being appended to the bottom of the file ~/DI.log (The stdbuf -oL prevents buffering of output to the file, so the file should update in real time)

Starting the configuration manager

Please see the "Starting up the CfgMgrApp on lbne35t-gateway01" section of Jon Paley's documentation here: https://cdcvs.fnal.gov/redmine/projects/fhicl_cfgmgr/wiki

Configuring and starting Runs

Now, you can take the DAQ system through the standard transitions to start a DAQ run. At all stages, you can use the "lbnecmd check" command to see what state DAQInterface is in; note that you'll want to wait for a transition to complete before issuing another one, otherwise you'll receive a warning and the transition request will be ignored. DAQInterface will also report to its log file when transitions are complete:

Initialize transition complete; if running DAQInterface in the background, can press <enter> to return to shell prompt

Note that if a high "debug level" has been set (see below for more on this), this message can get buried in a set of output messages; in this case "lbnecmd check" may be the easiest way to determine what state the system is in.

Selecting a run configuration and DAQ components

Before initializing or starting a DAQ run, a configuration and set of DAQComponents must be selected. This is done via RunControl.

List and select a configuration:

To see the list of available configurations (queried from the configuration manager):

lbnecmd listconfigs

Will return a list of configs:
Available configs (Name : description)

demo : Pithy description
tmp1 : Pithy description
...

Current selected config: No Config

This lists all available configs, as well as the current selected config (Note, default config is "No Config"). You can then select a configuration:
 
lbnecmd setconfig demo

This will return "OK" if successful; "lbnecmd listconfigs" will then show this as the current config. If the specified configuration is not known, an error is returned. Instructions on how to add a configuration are given later in this document.

List and select DAQ components.

You can select which portions of the LBNE DAQ setup you want to use in the upcoming run. These are mapped generally to the ArtDAQ BoardReaderMain processes
that read them out. As an operator, you need to ensure that there are configuration files available in the configuration manager for the DAQ Components that you select here, or DAQInterface will return an error.

To see the list of available DAQ components:

lbnecmd listdaqcomps

Will return a list of components available and selected (Default is ALL available components), e.g.:
{'available': {'component02': ['lbnedaq2', '5206'], 'component01': ['lbnedaq2', '5205']}}
{'selected': {'component02': ['lbnedaq2', '5206'], 'component01': ['lbnedaq2', '5205']}}

Shown are the available components by name, along with the requested host/port to run the BoardReaderMain process on. You can then select a list of DAQ components to use in the run:
lbnecmd setdaqcomps component01 component02

This will return "OK" if successful ("lbnecmd listdaqcomps" will show this in the "selected" row of components). If the specified compnents are not known, an error is returned.
To change the list of available components, see below.

Initializing, starting, stopping and terminating a Run

For each of these transitions, please recall that while "lbnecmd <cmd>" returns very quickly, the actual issued command can take several seconds or minutes to complete. Before issuing another command, be sure that the transition is complete by using the check command:

lbnecmd check

For example, before issuing the "start" transition, you can use this command to ensure that the DAQ is in the "ready" state and not still in the "initializing" stage.

First, take DAQInterface from the "stopped" to the "ready" state; this will create the artdaq processes on the hosts you selected (DAQ components), and initialize them with the FHiCL documents:

lbnecmd init daq

Take DAQInterface from the "ready" to the "running" state, in order to begin taking data:

lbnecmd start daq

Note: the current run number is displayed when DAQ is in the running state using the "lbnecmd check" command:
lbnecmd check
lbnecontrol: running
Run number: 207
Run configuration: demo

daqint@localhost:5570 (synchronous): running

Pause the running of the DAQ, putting DAQInterface into the "paused" state. This will cause the current open output file to be closed and given a name reflecting the current run number:

lbnecmd pause daq

Resume the running of the DAQ, putting returning to the "running" state. This will restart data taking to a new output file:

lbnecmd resume daq

Halt the running of the DAQ, returning DAQInterface to the "ready" state from the "running" state:

lbnecmd stop daq

From the ready state, you can start a new run with the same configuration and DAQ components you originally selected.
NOTE To select a new configuration or DAQ component set, you must kill all ArtDAQ processes and return DAQInterface to its "stopped" state with the "terminate" command:

lbnecmd terminate daq

If you want to stop all RunControl processes (known as "lbnecontrol"):

lbnecmd kill

After this, you will need to relaunch RunControl as above.

After your DAQ run.

Once you've completed your run, there are a few things you can look at.

The DAQ log

A record of the DAQ's output will be saved in the subdirectory pmt/ relative to where you specified the output logfiles; thus given the "log directory" setting in the example DAQInterface configuration file below, you'd find the output in /data/lbnedaq/daqlogs/pmt/.

The run record

Also, a record of the FHiCL documents sent to the artdaq processes, the configuration file used to control DAQInterface, and some further information will have been saved; as of this writing (12/3/14) the directory in which this can be found defaults to /data/lbnedaq/run_records/<run number>.
  • PLEASE NOTE that there may be slight differences between the saved FHiCL documents and the FHiCL documents specified in the DAQInterface configuration file (those that control the EventBuilderMain processes) and the run configuration (those that control the BoardReaderMain and AggregatorMain processes). The saved FHiCL document name is standardized to <processtype>_<host>_<port>_r<run number>.fcl, so, e.g, "EventBuilder_lbnedaq2_5235_r286.fcl" would be the saved name of /data/lbnedaq/fcl/EventBuilder_demo1.fcl, listed in the example DAQInterface configuration file above, assuming datataking was performed in run 286.
  • More importantly, the FHiCL document actually sent to the artdaq process may be slightly different than the FHiCL document provided for DAQInterface; this is because DAQInterface performs some bookkeeping on FHiCL variables which account for things such as the number of processes of a given type (note that it makes no changes which would affect the physics). It is this post-bookkeeping FHiCL document which actually gets sent to the processes which gets saved to the output directory.
  • The "further information" mentioned above is stored in a file of the form "metadata_r<run number>.txt"; it includes the configuration chosen for the run, the components used, as well as the commit hashes for the lbne-artdaq, lbnerc, and configuration directory used. E.g.,
    Config name: demo
    Component #0: component01
    Component #1: component02
    lbne-artdaq commit: 13b523181a6f8ff6e78ede590d6372ed6193c79c
    lbnerc commit: 288001cf015e1a763dbba482923fc7ac8f379ae6
    /data/lbnedaq/config commit: 877e43fe3ad96991adf5d57dbfbdefb6300fde25
    

Output of the Art modules

Various Art modules may create various types of output. In particular, it's standard for one of the two AggregatorMains running in an artdaq-based DAQ to use Art's RootOutput module, which will save the assembled raw event in an Art-readable *.root file. The location of this output can be found in the FHiCL code used to control RootOutput. The other AggregatorMain typically will run other RootOutput modules designed to create plots, diagnostic printouts, etc.; the nature of the output here is too varied to neatly summarize, but checking the FHiCL code used to control these Art modules should reveal their output location.

To take a quick look at the Art-readable *.root file, with a version of lbne-artdaq newer than 11/25/14, you can do the following:

cd <lbne-artdaq basedir>
source setupLBNEARTDAQ
rawEventDump -s <rootfile> -n <max events>

where here, <lbne-artdaq basedir> is the parent directory of the lbne-artdaq package, <rootfile> is the Art-readable *.root file produced in a given run, and <max events> is the max events whose info you wish to look at. The output of this command will look something like the following:

%MSG-i MF_INIT_OK:  art 01-Dec-2014 16:13:59 CST JobSetup 
Messagelogger initialization complete.
%MSG
%MSG-i PathConfiguration:  art 01-Dec-2014 16:14:00 CST JobSetup 
Multiple end paths have been combined into one end path,
"end_path" since order is irrelevant.

%MSG
01-Dec-2014 16:14:00 CST  Initiating request to open file /tmp/lbne35t_r000270_sr01_20141201T221127.root
01-Dec-2014 16:14:00 CST  Successfully opened file /tmp/lbne35t_r000270_sr01_20141201T221127.root
--------------------------------------------------------------
Package             |Version             |Timestamp           
artdaq-core         |v1_04_06            |01-Dec-2014 21:59:51 UTC
artdaq              |v1_12_04            |01-Dec-2014 22:01:57 UTC
lbne-artdaq         |v0_00_08            |01-Dec-2014 22:00:18 UTC
lbne-artdaq         |v0_07_00            |01-Dec-2014 22:02:57 UTC
--------------------------------------------------------------
Begin processing the 1st record. run: 270 subRun: 1 event: 1 at 01-Dec-2014 16:14:00 CST
PROCESS NAME | MODULE LABEL.. | PRODUCT INSTANCE NAME | DATA PRODUCT TYPE............ | PRODUCT FRIENDLY TYPE | SIZE
DAQ......... | daq........... | TOY1................. | std::vector<artdaq::Fragment> | artdaq::Fragments.... | ...2
DAQAG....... | TriggerResults | ..................... | art::TriggerResults.......... | art::TriggerResults.. | ...-

Total products (present, not present): 8 (2, 6).

PROCESS NAME | MODULE LABEL | PRODUCT INSTANCE NAME | DATA PRODUCT TYPE.................... | PRODUCT FRIENDLY TYPE.... | SIZE
DAQAG....... | BuildInfo... | LbneArtdaq........... | std::vector<artdaq::PackageBuildInfo> | artdaq::PackageBuildInfos | ...4

Total products (present, not present): 1 (1, 0).

01-Dec-2014 16:14:00 CST  Closed file /tmp/lbne35t_r000270_sr01_20141201T221127.root

TrigReport ---------- Event  Summary ------------
TrigReport Events total = 1 passed = 1 failed = 0

TrigReport ------ Modules in End-Path: end_path ------------
TrigReport  Trig Bit#    Visited     Passed     Failed      Error Name
TrigReport     0    0          1          1          0          0 printBuildInfo
TrigReport     0    0          1          1          0          0 out1

TimeReport ---------- Time  Summary ---[sec]----
TimeReport CPU = 0.003361 Real = 0.003000

Art has completed and will exit with status 0.

The first thing you see here is the version and build time of the lbne-artdaq package and some of the main packages on which it depends. Then you see a listing of products in the root file, here including two fragments of type TOY1, produced by the ToySimulator fragment generator. Finally, a listing of passed events; the output here is the result of running with "-n 1" as an option, so as we'd expect there's only one event.

Configuring DAQInterface: the DAQInterface configuration file

DAQInterface has some key information stored in a local configuration file, NOT to be confused with the run configuration described elsewhere on this wiki. Examples of this information are location and ports for artdaq processes, location of lbne-artdaq software, debug (log) level, etc). These can be changed before the DAQInterface process is started. It's expected that for normal operations, these should not need to changed too often, and alterations will be primarily of developer or expert interest. If you ARE a developer/expert or are simply curious, take a look at the default DAQInterface configuration file, found in docs/config.txt (relative to /data/lbnedaq/daqarea/lbnerc); it should look something like the following:


lbne-artdaq: /data/lbnedaq/daqarea/lbne-artdaq-base/build_lbne-artdaq

PMT host: lbnedaq3
PMT port: 5400

pause before initialization: 5

# debug level can range from 0 to 3 (increasing order of verbosity)
debug level: 1

log directory:   /data/lbnedaq/daqlogs

record directory: /data/lbnedaq/run_records

disable configuration check: false

TDU XMLRPC port: 0

EventBuilder host: lbnedaq2
EventBuilder port: 5235
EventBuilder fhicl: /data/lbnedaq/fcl/EventBuilder_demo1.fcl

EventBuilder host: lbnedaq2
EventBuilder port: 5236
EventBuilder fhicl: /data/lbnedaq/fcl/EventBuilder_demo2.fcl

Aggregator host: lbnedaq2
Aggregator port: 5265

Aggregator host: lbnedaq2
Aggregator port: 5266

The meaning of these parameters is as follows:

  • lbne-artdaq : the directory in which the desired build of lbne-artdaq to use is located
  • PMT host : the host on which artdaq's process management tool script (pmt.rb, used by DAQInterface to launch and kill the artdaq processes) will run
  • PMT port : pmt.rb's port
  • pause before initialization : the time in seconds between when the artdaq processes have been created and when they're initialized via FHiCL documents; empirically a pause of 5 seconds seems to be sufficient (less than this an errors can occur; see below in the "Troubleshooting" section for more
  • debug level : allows the user to set the verbosity level of the output to the screen; setting it to higher values creates greater verbosity, and as a practical matter, the range of settings is currently 0-3. Loosely speaking, "0" means minimal output (not much beyond simply announcing a transition is complete), "1" includes announcements of progress during transitions, "2" includes these announcements plus the values of certain variables as well as lbne-artdaq output, and "3" is primarily of developer interest.
  • log directory : the directory relative to which lbne-artdaq's pmt/*.log output (a record of what it sent to stdout) will be placed
  • record directory : the directory to which metadata about the run (FHiCL documents used, DAQInterface configuration file used, etc.) gets sent
  • disable configuration check : a boolean which can be set to "true" or "false"; normally this should be set to "false", which means that on the start transition, DAQInterface will intentionally fail and put itself into the "stopped" state if it discovers that edits have been made to the configuration directory since the last commit in that directory. If very frequent edits to the configuration directory are made during hardware debugging, however, switching this feature on to "true" can make life considerably easier.
  • TDU XMLRPC port : the value of the port through which DAQInterface will communicate with an XML-RPC server linked to the TDU. Needed for DAQInterface to send a sync pulse to the TDU at the beginning of the "start" and "resume" transitions. If this is set to 0 or a negative value, no sync pulse is attempted. For more on the TDU and its code, see Tom Dealtry's Wiki here

After these individual parameters, one defines the EventBuilderMain and AggregatorMain artdaq processes. Specifically, an EventBuilderMain is defined in three lines, where each line should contain "EventBuilder", and define the host and port on which the EventBuilderMain will run (to run an artdaq process on the same host as you're on, use "localhost") as well as the FHiCL document used to initialize the EventBuilderMain. AggregatorMain is defined similarly, using the token "Aggregator", but without the FHiCL document supplied, as this is supplied by the choice of configuration in the configuration manager. Best practice is to place the EventBuilderMain's FHiCL documents in the /data/lbnedaq/fcl directory. Please note that the order of processes matters, and that they should be listed front-end to back-end, i.e., EventBuilders should appear before Aggregators.

Adding new configurations to RunControl

Adding a new configuration selectable from RunControl involves two steps: creating a directory with the desired name of the configuration which contains the desired FHiCL documents, and then committing that directory to the git repository.

As of 11/20/14, the FHiCL documents associated with a given configuration are edited within the directory
/data/lbnedaq/config/<named_configuration>

where "named_configuration" would be the name of the configuration, in this example. Within this directory, the following files are expected:
  • Aggregator1.fcl and Aggregator2.fcl, used to initialize the two AggregatorMain processes in the DAQ system
  • <named_component>_hw_cfg.fcl, used to initialize the BoardReaderMain process running the fragment generator associated with detector component "named_component". Note that there can be any number of such files associated with a configuration, as long as a given component is registered to RunControl (see below, "Adding new DAQ Components to RunControl")

There are existing examples of configurations currently within /data/lbnedaq/config which can be studied (and even copied) for further guidance; however, please disregard the "tmp1" and "tmp2" configurations. Note that the FHiCL documents in these directories contain some variables which are set to "PLACEHOLDER", e.g.

 event_builder_count: PLACEHOLDER

Note that this is not legal FHiCL, but that DAQInterface will substitute in the appropriate value before using the FHiCL document to initialize an artdaq process; here, for example, it would replace "PLACEHOLDER" with the actual number of EventBuilderMain processes being run.

Once you've added a new configuration to /data/lbnedaq/config, you'll need to perform a git commit. Essentially, /data/lbnedaq/config is not merely a collection of directories naming configurations, but also a git repository. In fact, if you run
git log

you'll see a history of the commits made to the repository. In order to commit the directory, a couple of steps need to be taken:
  • From /data/lbnedaq/config/, run
    git add <named_configuration>
    . This will "stage" the directory to be committed. Running
    git status
    should show you something like the following:
    # On branch master
    # Changes to be committed:
    #   (use "git reset HEAD <file>..." to unstage)
    #
    #    new file:   helloworld/Aggregator1.fcl
    #    new file:   helloworld/Aggregator2.fcl
    #    new file:   helloworld/component01_hw_cfg.fcl
    #    new file:   helloworld/component02_hw_cfg.fcl
    #
    
  • Next, run
    git commit -m "<commit message>"
    . The commit message should be your three initials followed by a colon, the name of the configuration followed by a colon, and then a brief description of the new configuration, including its name, e.g.:
    git commit -m "JCF: helloworld: This configuration does not exist in the actual repo, it's simply used for documentation purposes" 
    

    Be aware of rules governing strings delimited by double quotes in bash -- i.e., don't try double quoting a word or phrase inside of your commit description.

    Now, make sure that the commit took place correctly by running
    git diff HEAD
    

    If your commit is at the head of the master branch, you should see no output; additionally, if you run
    git log
    

    you should be able to see your commit at the top.
  • Finally, make sure to push your change to the central repository; to do this, simply execute
    git push origin
    

and now, if you run

git diff origin/master

you should again see no output. Pushing to the central repository is important as this is essentially the backup area for configurations; if a user accidentally overwrites something in /data/lbnedaq/config, as long as commits have been pushed to the central repository there will still be a saved record of configurations before the overwrites took place. In fact, as of this writing (12/3/14), if either (A) edits have been made to the /data/lbnedaq/config directory since its most recent commit, or (B) that commit hasn't been pushed to the central repository, DAQInterface will refuse to execute the initialize transition.

Adding new DAQ Components to RunControl

The list of available DAQComponents (maps to BoardReader processes) is maintained by RunControl in the file:
/home/lbnedaq/.lbnerc-components

Each entry (name: host port) defines:
  • name - name of the component, maps to a <name>_hw_cfg.fcl in CfgMgr's configuration directory
  • host - hostname where BoardReader process will be started
  • port - XMLRPC port to be used, must be unique and used by other processes.

For example:

component01: lbnedaq2 5205
component02: lbnedaq2 5206

Has two components (component01 and component02) both running on lbnedaq2 on ports 5205 and 5206.

Troubleshooting and FAQ

Common RunControl issues

How can I get a list of all RunControl commands?

lbnecmd help

will list all available commands for RunControl with some details for help.

No real configurations are listed by RunControl

If you run "lbnecmd listconfigs" and see something like:

Available configs (Name : description)

dummy : Dummy description

Instead of your expected configurations, RunControl is not able to connect to CfgMgr. Please make sure it's running (https://cdcvs.fnal.gov/redmine/projects/fhicl_cfgmgr/wiki/Wiki)

Common DAQInterface issues

Error handling

As of this writing (11/14/14) certain potential problems have been anticipated and are handled within DAQInterface. These problems include:
  1. An artdaq process returns an error state after a transition request, or an exception is thrown by the XML-RPC library during the request
  2. During periodic checks, one or more artdaq processes expected to exist are not found

In either case, an error is reported via 0MQ to RunControl, and the "Recover" transition is automatically triggered. This transition is a fairly blunt instrument: it will kill any remaining artdaq processes and return DAQInterface to its original state of "stopped" (i.e., one in which it requires the "init" transition before anything else is done).

Your change to the DAQInterface configuration file or the daqinterface.py code doesn't seem to do anything

Make sure you kill the existing daqinterface process and restart it

On the initial transition ("lbnecmd init daq"), you see "error: [Errno 111] Connection refused"

If a "Recover" is triggered and you can see via "lbnecmd check" that DAQInterface is in the "stopped" state, try initializing again. If that doesn't work, you can try increasing the value of the "pause before initialization" variable in the DAQInterface configuration file. Empirically, it appears there needs to be a pause of at least 5 seconds before the FHiCL documents can be successfully sent via XML-RPC to the processes; increasing this value may make it less likely that the "Connection refused" error occurs.

On the initial transition, you see a regularly updating printout saying "Waiting for all processes to be launched"

Seeing one or two of these is fine. If, after several seconds, something like the following

Waiting for all processes to be launched; if zombie pmt.rb is running on localhost please kill it and this program (PID 31820)

keeps getting output to screen, it means there's a problem initializing. In this case, the current (11/12/14) course of action is to externally kill DAQInterface using the PID listed; also, it's possible that there may already be a pmt.rb executable running on the desired host, blocking the launch of a new one due to a port conflict, in which case you should log onto the host (assuming you're not already on it), and run
ps aux | grep -v grep | grep pmt.rb 

to see if this is the case. If it's not and you can't think of what might be wrong (is the configuration manager running? have you double-checked the DAQInterface configuration file?), then try increasing the debug level in the DAQInterface configuration file for your next run-through, as this will likely shed light on the nature of the problem.

Regardless of how high the debug level is set to, you don't see any output to screen when you issue transitions to DAQInterface

Chances are that DAQInterface was started in another terminal, and consequently, it's in that terminal where output will appear. This issue can be circumvented by redirecting DAQInterface output into a file; how this can be accomplished is described elsewhere in this document.