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Typically psmon is used for publishing results to realtime plots in the callback: Visualization Tools.

Running in LIVE mode

Here's a sample python script, how you can config datasource to run in live mode:

Code Block
languagepy
titlelivemode.py
# Use environment variable to specify how many attempts,
# the datasource should wait for file reading (1 second wait).
# In this example, we set it to 30 (wait up 30 seconds).
import os
os.environ['PS_SMD_MAX_RETRIES'] = '30'


# Create a datasource with live flag
from psana import DataSource
ds = DataSource(exp='tmoc00118', run=222, dir='/cds/data/psdm/prj/public01/xtc', 
        live        = True,
        max_events  = 10)


# Looping over your run and events as usual
# You'll see "wait for an event..." message in case
# The file system writing is slower than your analysis
run = next(ds.runs())
for i, evt in enumerate(run.events()):
    print(f'got evt={i} ts={evt.timestamp}')

Note that this script is also available in tests folder in lcls2 repository. You can run the script by:

Code Block
(ps-4.3.2) psanagpu109 tests $ mpirun -n 3 python livemode.py

MPI Task Structure

To allow for scaling, many hdf5 files are written, one per "SRV" node.  The total number of SRV nodes is defined by the environment variable PS_SRV_NODES (defaults to 0).  These many hdf5 files are joined by psana into what appears to be one file using the hdf5 "virtual dataset" feature.

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