Data Logger: Difference between revisions

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The Midas data logger serves multiple purpose of logging.
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# Its main task is to log experimental data to storage device[[Event_Filtering|(s)]] such as disk, tape, FTP.
<div style="column-count:4;-moz-column-count:4;-webkit-column-count:4">
# Serves the logging of the overall Midas system messages
* [[/Logger ODB tree]]
# Collect and log the history events
* [[mlogger]]
# Can log special information to an external mySQL database
* [[/Lazy ODB tree]]
* [[Lazylogger]]
</div>


logging System messages to a Message file or as message events
logging Experimental data to storage device(s) such as disk or tape
Multiple Logging Channels can be defined
several different storage devices, formats and compression levels can be selected
data can be logged to different subdirectories on disk
data can be logged to a remote computer, using the FTP mode
events can be selected for logging by Event ID or Trigger mask
Event Filtering can be implemented
runs can be automatically stopped and restarted after a certain number of events, or a certain time
the complete ODB contents can be saved
into a file at the beginning and/or end of run
and/or into the data stream
logging information to a mySQL database
writing information to an electronic logbook
collecting and logging history events
When the MIDAS logger (mlogger) is started for the first time, it creates the /Logger ODB tree (including a single logger channel - channel 0), and fills it with default settings. The /Logger tree contains all the relevant information for mlogger to run properly. The user has no code to write in order for the system to operate correctly. However, the user will want to customize the logger for his/her own experiment, by setting the keys in the /Logger tree to suitable values.




In addition to the /Logger tree, mlogger also creates the /History and /Elog ODB trees, used in the optional History and Electronic Logbook features. If MIDAS is compiled with mySQL support, a mySQL subtree will also be created in the /Logger tree (see Logging information to a mySQL database). All these features are described in the following pages.
The Midas [[mlogger|data logger]] serves multiple purposes related to data logging.
# On the fly data compression (if required)
# Log experimental data to storage device'''[[Event_Filtering|(s)]]'''
# Handles the overall Midas '''[[Message_System|System messages]]''' logging
# Collect and log the '''[[History System|history events]]'''
# Can log special information to an external '''[[Logging to a mySQL database|mySQL]]''' database


The data channels as well as the history logging are rescanned automatically at each start transition. In other words, additional logging channels can be defined while running, but the effect will take place only at the following start transition.
The data logger configuration is available in the ODB. Please refer to '''[[/Logger ODB tree]]''' for full feature descriptions.
The mlogger utility runs on the backend computer, receiving events from the buffer manager. It supports three type of storage devices so far, i.e.


Disk,
The actual application handling this Data logging is the '''[[mlogger]]'''. It is intended to run on the backend computer (on the same node where the event buffers reside) for fast data access (no network involved).
Tape
FTP channel to a remote computer.
Data can currently be written in five different formats :


MIDAS binary,
ASCII,
ROOT
DUMP
The user may of course write their own custom data logger to save the data in any format they choose.


'''Note:''' There is a '''[[Lazylogger|Data Archiver]]''' application which provide a copy or move of the logger data. The destination being usually a remote location holding a large data storage, tape robot, etc... The reason for such secondary logger is to off-load the local disk or decouple the '''[[mlogger|Data Logger]]''' application from possibly slow storage device.


 
[[Category:Data Logging]]
 
** [[Data storage options      &rarr; '' ''
** [[data compression]]      &rarr; ''''
** [[lazylogger|Secondary data logging]] (lazylogger)    &rarr; ''''

Latest revision as of 16:49, 14 July 2015



The Midas data logger serves multiple purposes related to data logging.

  1. On the fly data compression (if required)
  2. Log experimental data to storage device(s)
  3. Handles the overall Midas System messages logging
  4. Collect and log the history events
  5. Can log special information to an external mySQL database

The data logger configuration is available in the ODB. Please refer to /Logger ODB tree for full feature descriptions.

The actual application handling this Data logging is the mlogger. It is intended to run on the backend computer (on the same node where the event buffers reside) for fast data access (no network involved).


Note: There is a Data Archiver application which provide a copy or move of the logger data. The destination being usually a remote location holding a large data storage, tape robot, etc... The reason for such secondary logger is to off-load the local disk or decouple the Data Logger application from possibly slow storage device.

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