Offline framework for conditions data

1
Offline framework for conditions data

• L.Betev
• TPC commissioning meeting
• Geneva, February 17, 2006

2
Outline

• Conditions data in Offline
• Content and access
• Status of offline framework and plans

3
Conditions DB relations in ALICE

• Conditions data in Offline
• Conditions data are stored and accessible by the
  applications on the GRID
• Treating all source databases as potentially
  containing conditions information and as
  closed, i.e. only accessible at CERN
• It would be difficult to provide access methods
  to all DBs from the production and analysis code
• The conditions DB framework is providing access
  methods to all external DBs
• Conditions data stored as read only ROOT files
• Object store technology already incorporated in
  the ALICE offline

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Conditions DB relations in ALICE (2)

• Conditions data access in a Grid distributed
  production and analysis environment
• The root files are registered in the Grid
  Distributed File Catalogue
• No need for distributed DBMS in a traditional
  sense and with all accompanying problems (remote
  access, replication, authentication, load) a
  very big plus
• Assures worldwide access to all files and
  associated tags
• Drawbacks
• Replication of information potentially large
  parts of external DBs have to be put in the
  offline conditions DB
• However the same is true for all LHC experiments

5
External sources of conditions data and
relations to offline
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Conditions DB content and access

• Update frequency
• The condition DB will have rather infrequent
  updates (max once per run)
• The objects themselves can have rich internal
  structure with finer granularity, depending on
  the detector calibration / alignment needs
• Access framework
• Simple user interface and data identification
  (strings)
• Automatically get the right valid object
• Modification of the objects is handled through
  versioning
• Same interface for different types of data
  sources (local file, Grid)

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• Data organisation - simple filesystem-like
  storage
• Calibration/DETECTOR/FirstRun-LastRun.version

8
Status of the access framework

• AliRoot implementation
• Classes to put/get conditions objects are ready
  and tested by all ALICE detector groups
• Access methods
• GRID file and metadata storage (AliEn GRID File
  catalogue) deployed
• Conditions data dump in local files - expert use,
  new versions of conditions, disconnected from
  the GRID mode deployed
• Combination of the above - deployed

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Status of the access framework (2)

• Current issues
• Availability of conditions data
• Quasi-online first pass reconstruction good
  enough version of the conditions data should be
  available almost immediately
• Who provides what offline is a pure consumer of
  conditions data should make sure that the
  methods and procedures exist to store the data in
  the relevant external DBs
• APIs to external sources
• Access to some of the DBs not solved yet
  (especially LHC machine information)

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Conditions DB automatic information gathering

• Automated system Shuttle
• Collecting conditions data
• from external DB at predetermined
• time intervals (for example at
• the end of every run)
• Processing collected data
• using detector-specific preprocessor
• Storing conditions data in
• the Conditions DB

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Conditions DB information gathering (2)

• Similar systems can be used to process conditions
  data from other sources
• Only new interfaces needed
• The processing of the data is done in AliRoot (no
  change of framework)
• Allows detector groups to do analysis and
  reduction of the raw data volume before storing
  it in the Conditions DB
• The Shuttle program access to DCS and DAQ DBs is
  deployed and tested
• Real life test (Summer 2006) running with
  detector data ALICE TPC cosmic ray tests

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Summary on status and plans

• GRID/ROOT based Conditions DB framework ready
• Implementation in detector reconstruction and
  analysis code ongoing
• Automatic gathering of conditions data from
  external sources prototype ready
• Tests with real detector data Sumer 2006
• Continuous tests on the GRID as part of the
  ALICE PDC06/LCG SC4
• Current issues
• Availability of conditions data to offline from
  external sources
• good enough conditions data available for the
  first round of quasi-online processing

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Status of TPC