Keys in the ODB /Logger/Channels subtree

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/Logger/Channels subtree

The ODB /Logger/Channels subtree is a subdirectory of the ODB /Logger tree, created when the MIDAS logger utility mlogger is started for the first time. The keys will be filled with default values which users may change as required to customize their experiments.

By default, only one logging channel with the value 0 if defined (i.e. Logging Channel 0). Multiple logging channels may be defined by the user.




Multiple Logging Channels

By default, only one logging channel is created (Logging Channel 0). To create multiple logging channels, an existing Channel subtree can be copied.

e.g. to create a second logging channel (Channel 1) using odbedit

[local]cd /Logger
[loca]]logger>cd channels
[local]Channels>ls 
0
[local]Channels>copy 0 1
[local]Channels>ls 
0
1

If more than one logging channel is defined, there will be a multiple subtrees

  • /Logger/Channels/0/,
  • /Logger/Channels/1/,
  • ...

present, each with a Settings and Statistics subtree.

Thus the parameters for each logging channel can be set individually.

To send different events to different logging channels, they may be selected by Event ID key or Trigger mask key.




Settings subtree

The keys in the ODB /Logger/Channels/<logging-channel-number>/Settings subtree are shown below for the default logging channel 0.

For a single logging channel 0, one subtree

  • /Logger/Channels/0/Settings

will be present.


If multiple logging channels are defined, each will contain its own ODB Settings subtree,

i.e.

  • /Logger/Channels/0/Settings
  • /Logger/Channels/1/Settings




Active

  • Type: BOOL
  • Default: "y"

If this ODB key in the Settings subtree is set to "y", this logging channel is active. Data are only logged from channels that are active. Set to "n" to disable data logging from this channel.

Note that for data to be logged from any active logging channel, the /Logger/Write data key must also be set to "y".




Type

  • Type: STRING
  • Default: "Disk"

This ODB key in the Settings subtree specifies the type of media on which the logging should take place. It can be "Disk", "Tape" or "FTP" (see Filename key).




Filename

  • Type: STRING
  • Default: "run%05d.mid"

This ODB key in the Settings subtree is set up as follows:

For disk logging 
ODB key Filename specifies the name of a file to contain the data. Default value is "run%05d.mid" where "%05d" is replaced by the current run number in the same way as described for the ODB key /Logger/Dump File. If subruns are enabled, the filename may be of the form "run%05d_%02d.mid". See subruns for details.
 
The key Filename may contain a directory string in addition to a filename, so that different logging channels may have their data logged into specific directories. If the key does NOT also contain a directory string, the directory given in the key /Logger/Data dir key will be used. The contents of the key Filename must match that of the Format key.
For tape logging 
key Filename specifies a tape device i.e.
  • /dev/nrmt0 or /dev/nst0 under UNIX or
  • \\.\tape0 under Windows NT.
WARNING: tape logging is no longer maintained
FTP mode 
the data is written directly to a remote computer via FTP. Key Filename specifies the access information for the FTP server. It has the following format:
 <host name>, <port number>, <user name>, <password>, <directory>, <file name>
for example
 myhost.my.domain,21,john,password,/usr/users/data,run%05d.mid

The normal FTP port number is 21, or 1021 for a Unitree Archive like the one used at the Paul Scherrer Institute.

By using the FTP mode, a back-end computer can write directly to the archive.




Format

  • Type: STRING
  • Default: "MIDAS"

This ODB key in the Settings subtree specifies the format to be used for writing the data to the logging channel. It can take one of four values: MIDAS, ROOT, ASCII and DUMP.

For disk logging, the extension for the Filename key above must match one of the following:

  • .mid for MIDAS (or .mid.gz - see Compression key)
  • .root for ROOT
  • .asc for ASCII
  • .txt for DUMP

For ROOT format the data logger will automatically convert the format specified in the frontend equipment list to ROOT format (see format for details). The ASCII format converts events into readable text format which can be easily analyzed by programs that have problems reading binary data. While the ASCII format tries to minimize the file size by printing one event per line, the DUMP format gives a very detailed ASCII representation of the event including bank information, serial numbers etc., so it should be used mainly for diagnostics.




Compression

  • Type: INT
  • Default: 0


This ODB key in the Settings subtree defines the Compression Level of the data. If set to 0, compression is turned off. If set > 0, the data files are compressed before being written. In this case,

  • the file extension ".gz" must be appended to the Filename key (see also Format key)
  • and ZLIB support must be compiled into the MIDAS package (see NEED_ZLIB ).

This feature applies only to files saved onto disk in MIDAS format. ROOT format is already compressed.




ODB Dump

  • Type: BOOL
  • Default: "y"


If this ODB key in the Settings subtree is set to "y", a complete dump of the ODB is performed to this logging channel before and after every run. The format of the ODB dump is set by the key #ODB dump format. The ODB content is reflects the status at begin-of-run event and at end-of-run event. These special events have an ID of EVENTID_BOR (0x8000) and EVENTID_EOR (0x8001) (defined in midas.h) and a serial number equal to the current run number, and are not visible using the mdump utility. An analyzer in the off-line analysis stage can use these special events to restore the ODB to its online state.

The dump of the ODB into the event stream for this logger channel is independent of the /Logger/ODB Dump key, which is used to dump the ODB to a file on disk in the specified format.




ODB dump format

  • Type: STRING
  • Default: "json"

This ODB key in the Settings subtree defines the format of the ODB Dump file, providing the ODB key #ODB Dump is set to "y". The default is now "json" (since March 2019) and the filename of the odb dump file saved at end-of-run is is "last.json".

Users who wish to use "xml" should set this key to "xml" and Keys in the ODB /Logger tree#ODB Last Dump File to "last.xml".




Log messages

  • Type: DWORD
  • Default: 0

This ODB key in the Settings subtree is a bit-field for logging system messages as message events along with the event data from the experiment. If a bit in this field is set, the respective system message is written to the logging channel as a message event with an ID of EVENTID_MESSAGE (0x8002) (defined in midas.h). The bits are 1 for error, 2 for info, 4 for debug, 8 for user, 16 for log, 32 for talk, 64 for call messages and 255 to log all messages. For an explanation of these messages refer to Buffer Manager , Event ID key and Trigger mask key.






Buffer

  • Type: STRING
  • Default: "SYSTEM"


This ODB key in the Settings subtree specifies the buffer where the logger will find the event. It is usually set to "SYSTEM" and is specified in the equipment list for this event.




Event ID

  • Type: INT
  • Default: -1


This ODB key in the Settings subtree contains the ID of the event(s) to be logged (see EventID). It is specified in the Equipment List for this event.

To log events with any ID, Event ID is set to -1 (EVENTID_ALL). Event ID key and/or Trigger mask key may be used to select events to be sent to different logging channels, or as an Event Filtering system.




Trigger mask

  • Type: INT
  • Default: -1

This ODB key in the Settings subtree specifies which events to log based on the Trigger Mask of the event. It is specified in the Equipment List of this event.

For a logging channel to receive all events, -1 is used for both the Event ID key and the Trigger mask key .

Either the Trigger Mask or Event ID key may be used to select events to be sent to particular logging channels, or for Event Filtering.




Event limit

  • Type: DOUBLE
  • Default: 0


The value of this ODB key Event limit in the Settings subtree can be used to stop a run when set to a non-zero value. The statistics value Events written is checked against the Event limit value. When this condition is reached, the run is stopped automatically by the data logger mlogger. The next run can then be started automatically if desired (see Auto restart).





Byte limit

  • Type: DOUBLE
  • Default: 0


The value of this ODB key Byte limit in the Settings subtree can be used to stop a run when set non-zero. The statistics value Bytes written is checked against the Byte limit value. When this conditions is reached, the run is stopped automatically by the data logger mlogger. The next run can then be started automatically if desired (see Auto restart). ).




Subrun Byte limit

  • Type: DOUBLE
  • Default: 0


The value of the ODB key Subrun Byte limit in the Settings subtree can be used to stop a subrun when set non-zero. When this condition is reached, the run is stopped automatically by the data logger (mlogger). The next run can then be started automatically if desired (see Auto restart).




Tape capacity (obsolete)

  • Type: DOUBLE
  • Default: 0

The value of the ODB key Tape capacity in the Settings subtree can be used to stop a run when set to non-zero. The value in the key Bytes written total is checked against the limit set by Tape capacity. When this condition is reached, the run is stopped automatically by the data logger.

Warning: writing directly to tape is not maintained




Subdir format

  • Type: STRING
  • Default:


This ODB key in the Settings subtree optionally specifies a subdirectory, which is appended to the directory string in the key Filename.

It is used to place the data log file into a date-stamped subdirectory. This is useful where a large numbers of data files are produced, or experiments are active for a long time, and it is desirable to store the data in sub-directories according to their date. This can be done automatically using the Subdir format key.

If the Subdir format key is not empty, the data log file will be placed in a subdirectory. The name of this subdirectory is composed by the given Subdir format string. Its format follows the definition of the system call strftime() . (See man strftime). Ordinary characters placed in the format string are copied to the output character array "s" without conversion. Conversion specifiers are introduced by a '%' character, and are replaced in "s" as follows for the most common ones:

  •  %Y : Year (ex: 2002)
  •  %y : Year (range:00..99)
  •  %m : Month (range: 01..12)
  •  %d : Day (range: 00..31)

The other characters are: %a, %A, %b, %B, %c, %C, %d, %D, %e, %E, %G, %g, %h, %H, %I, %j, %k, %l, %m, %M, %n, %O, %p, %P, %r, %R, %s, %S, %t, %T, %u, %U, %V, %w, %W, %x, %X, %y, %Y, %z, %Z, %+. (See man strftime for explanation).





Current filename

  • Type: STRING
  • Default:

This ODB key in the Settings subtree will reflect the full path of the current saved data file.





Data checksum

  • Type: STRING
  • Default: CRC32C

This ODB key in the Settings subtree can be set to one of: NONE CRC32C SHA256 SHA512 ZLIB.

See Note on defaults under #Compress below.




File checksum

  • Type: STRING
  • Default: CRC32C

This ODB key in the Settings subtree can be set to one of: NONE CRC32C SHA256 SHA512 ZLIB.

See Note on defaults under #Compress below




Compress

  • Type: STRING
  • Default: lz4

This ODB key in the Settings subtree can be set to one of : none gzip lz4 bzip2 pbzip2.

Note

The defaults of "free" compression (LZ4) and output file data integrity protected by checksums (CRC32C) are "free" in the sense that turning them off would not noticeably improve the system performance. (Some users may want to enable better compression, such as BZIP2 or PBZIP2 and better checksums, such as SHA256 or SHA512 - both choices that have significant CPU-use cost).




Output

  • Type: STRING
  • Default: FILE

This ODB key in the Settings subtree can be set to one of: NULL FILE FTP ROOT PIPE.



Statistics subtree

The keys in the ODB /Logger/Channels/<logging-channel-number>/Statistics subtree are shown below for the default logging channel 0.

For a single logging channel 0, one ODB subtree

  • /Logger/Channels/0/Statistics

will be present.


If multiple logging channels are defined, each will contain its own ODB Statistics subtree,

i.e.

  • /Logger/Channels/0/Statistics
  • /Logger/Channels/1/Statistics




Events written

  • Type: DOUBLE
  • Default: 0

This ODB key in the Statistics subtree contains the number of events written. Cleared at begin-of-run. Events written statistics are used to determine when to stop a run automatically by checking against the Event limit key.




Bytes written

  • Type: DOUBLE
  • Default: 0


This ODB key in the Statistics subtree contains the number of bytes written. Cleared at begin-of-run. Bytes written statistics are used to determine when to stop a run automatically by checking against the Byte limit key.





Bytes written uncompressed

  • Type: DOUBLE
  • Default: 0

If Compression level is 0 (i.e. data not compressed), the values of the ODB keys in the Statistics subtree Bytes written uncompressed and Bytes written will be identical.





Bytes written total

  • Type: DOUBLE
  • Default: 0


This ODB key in the Statistics subtree contains the total number of bytes written. Cleared only when a tape is rewound with the odbedit command rewind. The Bytes written total entry can therefore be used as an indicator of when a tape is full by checking against the limit Tape Capacity.

Warning: writing directly to tape is not maintained




Files written

  • Type: INT
  • Default: 0

This ODB key in the Statistics subtree contains the number of files written. Cleared only when a tape is rewound with the odbedit command rewind. Files written value can be used off-line to determine how many files on a tape have to be skipped in order to reach a specific run.

Warning: writing directly to tape is not maintained