Welcome to NXSDataWriter's documentation!

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Authors: Jan Kotanski, Eugen Wintersberger, Halil Pasic

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Introduction

NXSDataWriter is a Tango server which allows to store NeXuS Data in H5 files.

The server provides storing data from other Tango devices, various databases as well as passed by a user client via JSON strings.

Tango Server API: https://nexdatas.github.io/nxsdatawriter/doc_html

| Source code: https://github.com/nexdatas/nxsdatawriter | Project Web page: https://nexdatas.github.io/nxsdatawriter | NexDaTaS Web page: https://nexdatas.github.io

---

Installation

Install the dependencies:

| pninexus or h5py, tango, numpy, nxstools, sphinx

From sources """"""""""""

Download the latest NexDaTaS version from

| https://github.com/nexdatas/nxsdatawriter

Extract sources and run

.. code-block:: console

  $ python setup.py install

Debian packages """""""""""""""

Debian bookworm, bullseye, buster or Ubuntu lunar, jammy, focal packages can be found in the HDRI repository.

To install the debian packages, add the PGP repository key

.. code-block:: console

  $ sudo su
  $ curl -s http://repos.pni-hdri.de/debian_repo.pub.gpg | gpg --no-default-keyring --keyring gnupg-ring:/etc/apt/trusted.gpg.d/debian-hdri-repo.gpg --import
  $ chmod 644 /etc/apt/trusted.gpg.d/debian-hdri-repo.gpg

and then download the corresponding source list

.. code-block:: console

  $ cd /etc/apt/sources.list.d
  $ wget http://repos.pni-hdri.de/bookworm-pni-hdri.list

To install tango server

.. code-block:: console

  $ apt-get update
  $ apt-get install nxswriter

or

.. code-block:: console

  $ apt-get update
  $ apt-get install nxswriter3

for older python3 releases.

To install only the python3 package

.. code-block:: console

  $ apt-get update
  $ apt-get install python3-nxswriter

and for python2

.. code-block:: console

  $ apt-get update
  $ apt-get install python-nxswriter

if exists.

From pip """"""""

To install it from pip you can

.. code-block:: console

$ python3 -m venv myvenv $ . myvenv/bin/activate

$ pip install nxswriter

Moreover it is also good to install

.. code-block:: console

$ pip install pytango $ pip install pymysqldb $ pip install psycopg2-binary $ pip install cx-oracle

Setting NeXus Writer Server """""""""""""""""""""""""""

To set up NeXus Writer Server run

.. code-block:: console

      $ nxsetup -x NXSDataWriter

The nxsetup command comes from the python-nxstools package.

---

Client code

In order to use Nexus Data Server one has to write a client code. Some simple client codes are in the nexdatas repository. In this section we add some comments related to the client code.

.. code-block:: python

To use the Tango Server we must import the tango module and

create DeviceProxy for the server.

import tango

device = "p09/tdw/r228" dpx = tango.DeviceProxy(device) dpx.set_timeout_millis(10000)

dpx.Init()

Here device corresponds to a name of our Nexus Data Server.

The Init() method resets the state of the server.

dpx.FileName = "test.h5" dpx.OpenFile()

We set the name of the output HDF5 file and open it.

Now we are ready to pass the XML settings describing a structure of

the output file as well as defining a way of data storing.

Examples of the XMLSettings can be found in the XMLExamples directory.

with open("test.xml", 'r') as fl: xml = fl.read() dpx.XMLSettings = xml

dpx.JSONRecord = '{"data": {"parameterA":0.2}, "decoders":{"DESY2D":"desydecoders.desy2Ddec.desy2d"}, "datasources":{ "MCLIENT":"sources.DataSources.LocalClientSource"} }'

dpx.OpenEntry()

We read our XML settings settings from a file and pass them to the server via

the XMLSettings attribute. Then we open an entry group related to the XML

configuration. Optionally, we can also set JSONRecord, i.e. an attribute

which contains a global JSON string with data needed to store during opening

the entry and also other stages of recording. If external decoder for

DevEncoded data is need one can registred it passing its packages and

class names in JSONRecord,

e.g. "desy2d" class of "DESY2D" label in "desydecoders.desy2Ddec" package.

Similarly making use of "datasources" records of the JSON string one can

registred additional datasources. The OpenEntry method stores data defined

in the XML string with strategy=INIT.

The JSONRecord attribute can be changed during recording our data.

After finalization of the configuration process we can start recording

the main experiment data in a STEP mode.

dpx.Record('{"data": {"p09/counter/exp.01":0.1, "p09/counter/exp.02":1.1}}')

Every time we call the Record method all nexus fields defined with

strategy=STEP are extended by one record unit and the assigned to them data

is stored. As the method argument we pass a local JSON string with the client

data. To record the client data one can also use the global JSONRecord string.

Contrary to the global JSON string the local one is only

valid during one record step.

dpx.Record('{"data": {"emittance_x": 0.1}, "triggers":["trigger1", "trigger2"] }')

If you denote in your XML configuration string some fields by additional

trigger attributes you may ask the server to store your data only in specific

record steps. This can be helpful if you want to store your data in

asynchronous mode. To this end you define in the local JSON string a list of

triggers which are used in the current record step.

dpx.JSONRecord = '{"data": {"parameterB":0.3}}' dpx.CloseEntry()

After scanning experiment data in 'STEP' mode we close the entry.

To this end we call the CloseEntry method which also stores data defined

with strategy=FINAL. Since our HDF5 file can contain many entries we can again

open the entry and repeat our record procedure. If we define more than one entry

in one XML setting string the defined entries are recorded parallel

with the same steps.

Finally, we can close our output file by

dpx.CloseFile()

Additionally, one can use asynchronous versions of OpenEntry, Record, CloseEntry, i.e. OpenEntryAsynch, RecordAsynch, CloseEntryAsynch. In this case data is stored in a background thread and during this writing Tango Data Server has a state RUNNING.

In order to build the XML configurations in the easy way the authors of the server provide for this purpose a specialized GUI tool, Component Designer. The attached to the server XML examples was created by XMLFile class defined in XMLCreator/simpleXML.py.