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Configuration Server for Nexus Data Writer

Project description

Welcome to NeXuS Configuration Server’s documentation!

Authors: Jan Kotanski, Eugen Wintersberger, Halil Pasic

NeXuS Configuration Server is a Tango Server with its implementation based on a MySQL database. It allows to store XML configuration datasources and components. It also gives possibility to select mandatory components and perform the process of component merging.

Tango Server API:


Install the dependencies:

MySQLdb, PyTango, sphinx

From sources

Download the latest version of NeXuS Configuration Server from

Extract the sources and run

$ python install

To set database execute

$ mysql < conf/mysql_create.sql

with proper privileges.

Debian packages

Debian Buster (and Stretch) as well as Ubuntu Focal (and Bionic) packages can be found in the HDRI repository.

To install the debian packages, add the PGP repository key

$ sudo su
$ wget -q -O - | apt-key add -

and then download the corresponding source list, e.g. for buster

$ cd /etc/apt/sources.list.d
$ wget

Finally, for python2 packages

$ apt-get update
$ apt-get install python-nxsconfigserver nxsconfigserver-db

and the NXSConfigServer tango server (from 2.10.0)

$ apt-get install nxsconfigserver

or for python3

$ apt-get update
$ apt-get install python3-nxsconfigserver nxsconfigserver-db

and the NXSConfigServer tango server (from 2.10.0)

$ apt-get install nxsconfigserver3
From pip

To install it from pip you need pymysqldb e.g.

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

$ pip install pymysqldb

$ pip install nxsconfigserver

Moreover it is also good to install

$ pip install pytango
$ pip install nxstools

Setting NeXus Configuration Server

To set up NeXus Configuration Server with the default configuration run

$ nxsetup -x NXSConfigServer

The nxsetup command comes from the python-nxstools package.


Configuration Server is dedicated to store NXDL-like configuration needed for Tango Data Writer runs. The server uses as a storage system a MYSQL database. To create required DB tables one can use ndts.sql script from the repository.

In Configuration Server the configuration is memorized in separate elements: datasources or components.

DataSources describe access to input data, i.e to specific hardware TANGO devices or other databases as well to client data.

Components specify Nexus tree with positions of datasets for particular pieces of hardware and writing strategy for corresponding to them data.

  • They can include datasources directly as well as links to datasources defined in the server. To this end template syntax of $datasources.<ds_name> type is used.
  • Moreover, they can holds links to other components which describe their dependences. In this case $components.<comp_name> syntax is used.
  • Finally, the components can contains variables. The variables are defined in XML code by $var.<var_name> syntax and can be provided to the Configuration Server by passing a JSON string. The default value for variables is an empty string.

All elements of configuration can be created by GUI tool - ComponentDesigner. The tool can connect to Configuration Server and fetch or store the separate elements of the XML configuration.

During creation of the final configuration Configuration Server merges all required and dependent components, connected to them datasources and provided values of the variables. As a result it returns a single XML string. This XML string can be pass directly into the dedicated Tango Data Writer attribute.

Client code

# In this section we present an example how to communicate with
# Configuration Server making use of PyTango.

import PyTango

cnfServer = PyTango.DeviceProxy("p00/xmlconfigserver/exp.01")

cnfServer.JSONSettings = \

# opens DB connection

# After creating the server proxy we can set configuration for connection to
#  the MYSQL DB.
# The JSONSettings attribute is memorized so you have to write it only when you
# change configuration of DB connection. Next, we open connection to
# DB specified by our JSONSettings.

# stores default component
cpxml = open("default.xml", 'r').read()
cnfServer.XMLString = cpxml

# stores slit1 component in DB
cpxml = open("slit1.xml", 'r').read()
cnfServer.XMLString = cpxml

# stores slit2 component in DB
cpxml = open("slit2.xml", 'r').read()
cnfServer.XMLString = cpxml

# stores slit3 component in DB
cpxml = open("slit3.xml", 'r').read()
cnfServer.XMLString = cpxml

# stores pilatus300k component in DB
cpxml = open("pilatus.xml", 'r').read()
cnfServer.XMLString = cpxml

# stores motor01 datasource in DB
dsxml = open("motor.ds.xml", 'r').read()
cnfServer.XMLString = dsxml

# stores motor02 datasource in DB
dsxml = open("motor.ds.xml", 'r').read()
cnfServer.XMLString = dsxml

# removes slit3 component from DB

# removes motor02 datasource from DB

# If someone cannot use ComponentDesigner it is also an option to store
# or delete components and datasources using directly tango interface
# as it is shown above.

# provides names of available components
cmpNameList = cnfServer.AvailableComponents()
# provides names of available datasources
dsNameList = cnfServer.AvailableDataSources()

# To get information about names of available components and datasources
# in Configuration Server we use the above commands.

# provides a list of required components
cmpList = cnfServer.Components(cmpNameList)
# provides a list of required Datasources
dsList = cnfServer.DataSources(dsNameList)

# Having names of stored elements we can get their XML code.

# provides a list of Datasources from a given Component
dsList = cnf.Server.ComponentDataSources('pilatus300k')
dsList = cnf.Server.ComponentsDataSources(['pilatus300k', 'slit1'])

# as well as query Configuration Server which datasource
# are related to the particular component.

# provides a dependent components
cpList = cnf.Server.DependentComponents(['pilatus300k', 'slit3'])

# Moreover, one can also query Configuration Server for a list of
# dependent components

# provides a list of Variables from a given components
varList = cnf.Server.ComponentVariables('pilatus300k')
varList = cnf.Server.ComponentsVariables(['pilatus300k', 'slit3'])

#or ask for a list of variables which are related to the particular components.

# sets values of variables
cnf.Server.Variables = '{"entry_id":"123","beamtime_id":"123453535453"}'

#The variable values can be passed to the Configuration Server
# via a JSON string.

# sets given component as mandatory for the final configuration
# un-sets given component as mandatory for the final configuration

# provides names of mandatory components
man =  cnfServer.MandatoryComponents()

# Some of the component can be set as mandatory in
# the final configuration. To define them Configuration Server provides
# above commands.

# provides the current configuration version
version =  cnfServer.Version

# Each configuration has a revision number. It can be found
# together with Configuration Server version in Version attribute.

# creates the final configuration from slit2 and pilatus300k
# as well as all mandatory components
cnfServer.CreateConfiguration('slit2', 'pilatus300k')
# XML string ready to use by Tango Data Server
finalXML = cnfServer.XMLString

# In order to create our final configuration we execute CreateConfiguration
# command with a list of names of required components. The command merges
# these components with mandatory ones and provides the resulting NXDL-like
# configuration in the XMLString attribute.

# merges given components
mergedComp = cnfServer.Merge(['slit2', 'pilatus300k'])

# Similarly, the Merge command provides configuration by unresolved links
# to datasoures and with non-assigned variable values.

# closes connection to DB

# Command close terminates our connection to the DB server.

Configuration Variables

Values of configuration variables can be also define inside the component xmls. Let’s consider two following components:

mydetector with a general detector transformation group

  <group type='NXentry' name='entry'>
    <group type='NXinstrument' name='instrument'>
       <group type='NXdetector' name='$var.detector#\"mydetector\"'>
          <group type='NXtransformations' name='transformations'/>

and pilatus created for the particular detector

  <group type='NXentry' name='entry'>
    <group type='NXinstrument' name='instrument'>
       <group type='NXdetector' name='pilatus'>
          <field type='NX_FLOAT64' name='data'/>

Creating configuration without variables

cnfServer.Variables = '{}'

results in

  <group type='NXentry' name='entry'>
    <group type='NXinstrument' name='instrument'>
       <group type='NXdetector' name='mydetector'>
          <group type='NXtransformations' name='transformations'/>

When configuration variables are defined

cnfServer.Variables = '{"detector": "det1"}'

one can get

  <group type='NXentry' name='entry'>
    <group type='NXinstrument' name='instrument'>
       <group type='NXdetector' name='det1'>
          <group type='NXtransformations' name='transformations'/>

Finally, creating configuration xml from our two components without variables

cnfServer.Variables = '{}'
cnfServer.CreateConfiguration(["mydetector", "pilatus"])

results in

<group name="entry" type="NXentry">
  <group name="instrument" type="NXinstrument">
    <group name="pilatus" type="NXdetector">
      <group name="transformations" type="NXtransformations"/>
      <field name="data" type="NX_FLOAT64"/>

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