/Lazy ODB tree

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Creating the /Lazy tree

This tree is created with default parameters on the first activation of the lazylogger utility . This task connects to a defined channel (e.g. Tape, Disk) when started. Multiple instances of the program can run concurrently, connecting to a different channel (see lazylogger above).

The following example shows a /Lazy tree with a <channel-name> of "Disk". A sub-tree /Lazy/Disk has been created, containing sub-trees "Settings" and "Statistics". A third sub-tree "List" will be created after the first successful operation of the channel. The contents of these sub-trees is discussed below (see Settings, Statistics and List subtrees.) 

[local:pol:S]/>ls /lazy/disk
Settings
Statistics
List

Example of the ODB /Lazy/<channel_name>/Settings subtree

The following example shows a typical /Lazy ODB tree obtained using the odbedit "ls" command. See keys in the ODB /Lazy tree for more information on each key. 

  Settings                      DIR
       Maintain free space(%)    INT     1     4     3m   0   RWD  0
       Stay behind               INT     1     4     3m   0   RWD  -3
       Alarm Class               STRING  1     32    3m   0   RWD  
       Running condition         STRING  1     128   3m   0   RWD  ALWAYS
       Data dir                  STRING  1     256   3m   0   RWD  /home/midas/online
       Data format               STRING  1     8     3m   0   RWD  MIDAS
       Filename format           STRING  1     128   3m   0   RWD  run%05d.mid
       Backup type               STRING  1     8     3m   0   RWD  Tape
       Execute after rewind      STRING  1     64    3m   0   RWD  
       Path                      STRING  1     128   3m   0   RWD  
       Capacity (Bytes)          FLOAT   1     4     3m   0   RWD  5e+09
       List label                STRING  1     128   3m   0   RWD  
 Execute before writing file     STRING  1     64    11h  0   RWD  lazy_prewrite.csh
 Execute after writing file      STRING  1     64    11h  0   RWD  rundb_addrun.pl
 Modulo.Position                 STRING  1     8     11h  0   RWD  2.1
 Tape Data Append                BOOL    1     4     11h  0   RWD  y


Explanation of the Keys in the ODB /Lazy/<channel_name>/Settings subtree

An example of the subtree is shown above.

Maintain free space(%)

  • Type: INT
  • Default: 0


As the data Logger (mlogger) runs independently from the Lazylogger, the data logging device (e.g. disk) contains all the recorded data files. Under this condition, Lazylogger can be instructed to "purge" the disk after successful backup of the data onto a "slow device" (e.g. tape).

This parameter Maintain free space(%) in the ODB /Lazy/<channel_name>/Settings subtree controls the percentage of disk space required to be maintained as free (for "none" set to 0).

  • The conditions that must ALL be satisfied before removing a data file are defined as:
  1. The data file corresponding to the given run number following the format declared under Settings/Filename format IS PRESENT on the Settings/Data Dir path.
  2. The given run number MUST appear anywhere under the Settings/List/ directory of ALL the Lazy channels having the same Settings/Filename format as this channel.
  3. The given run number MUST appear anywhere under the Settings/List/ directory of that channel


Stay behind

  • Type: INT
  • Default: 0


This parameter in the ODB /Lazy/<channel_name>/Settings subtree defines how many consecutive data files should be kept between the current run and the last lazylogger run.

Example with "Stay behind = -3"
Current acquisition run number 253 -> run00253.mid is being logged by mlogger.
Files available on the disk corresponding to runs #248, #249, #250, #251, #252.
Lazylogger will start backing up run #250 as soon as the new run 254 starts.
"Stay behind = -3" corresponds to 3 files untouched on the disk (#251, #252, #253).
If the sign (+/-) of the "Stay behind" parameter is
negative: the lazylogger will always scan the entire disk at the "Data Dir" path, from the oldest to the most recent file present for backup.
positive: lazylogger will backup starting from -x behind the current acquisition run number. Run order will be ignored.


Alarm Class

  • Type: STRING
  • Default: ""


This parameter in the ODB /Lazy/<channel_name>/Settings subtree defines specify the Alarm class to be used in case of an alarm being triggered.


Running Condition

  • Type: STRING
  • Default: "ALWAYS"


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies the type of condition for which the lazylogger should be actived. By default the lazylogger is ALWAYS running.

The choices are
ALWAYS, NEVER, WHILE_NO_ACQ_RUNNING,
or a condition based on a single field of the ODB key<=>value

Example : In the case of high data rate acquisition it could be necessary to activate the lazylogger only

  • when the run is either paused or stopped (i.e. WHILE_NO_ACQ_RUNNING)
     odbedit > set "Running condition" WHILE_ACQ_NOT_RUNNING
  • or when some external condition is satisfied such as "low beam intensity".
     odbedit> set "Running condition" "/alias/max_rate < 200"


Data Dir

  • Type: STRING
  • Default: ""


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies the data directory path of the data logging device (e.g. disk). If this key is present, the contents is taken as the path, otherwise the current directory is used (i.e. the path where the lazylogger client was started).


Data format

  • Type: STRING
  • Default: "MIDAS"


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies the data format of the data files. See Format.


Filename format

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


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies the filename format of the data files on the data logging device (i.e. disk). This should be the same filename format as used by the data logger to save the files (see Filename).


Backup Type

  • Type: STRING
  • Default: "Tape"


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies the type of the "backup device" to be used for the lazylog backup. It can be "Disk","Tape" or "Ftp".


Execute after rewind

  • Type: STRING
  • Default: ""


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies an optional script to run after completion of a lazylogger backup set (see below #Capacity (Bytes)).


Path

  • Type: STRING
  • Default: ""


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies the backup device path.

There are three possible types of Path:

  • For Tape : e.g. /dev/nst0- (UNIX like).
  • For Disk : e.g. /data1/myexpt
  • For Ftp : host,port,user,password,directory


Capacity (Bytes)

  • Type: FLOAT
  • Default: 5e9


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies the maximum backup device capacity in bytes. When this capacity is reached,the lazylogger will close the backup device and clear the List label field to prevent further backup. It will also rewind the stream device if possible.

List label

  • Type: STRING
  • Default: ""


This parameter in the ODB /Lazy/<channel_name>/Settings subtree specifies a label for a set of backed up files to the backup device. This label is used internally by the lazylogger for creating a new array composed of the backed up runs under the /Settings/List subdirectory, until the Capacity value has been reached. Once the backup set is complete, lazylogger will clear the "List label" field and therefore prevent any further backup until a non-empty "List label" is re-entered. However, the list label will remain under the /Settings/List key to display all run being backed up until the corresponding files have been removed from the disk.

Execute before writing file

  • Type: STRING
  • Default: ""


This parameter in the ODB /Lazy/<channel_name>/Settings subtree permits a script to be run before the beginning of the lazy job. The arguments passed to the script are: input file name , output file name, current block number.

Execute after writing file

  • Type: STRING
  • Default: ""


This parameter in the ODB /Lazy/<channel_name>/Settings subtree permits a script to be run after the completion of the lazy job. The arguments passed to the scripts are: list label, current job number, source path, file name, file size in MB, current block number.


Modulo.Position

  • Type: STRING
  • Default: ""


This field in the ODB /Lazy/<channel_name>/Settings subtree is for multiple instances of the lazylogger where each instance works on a sub-set of run number. By specifying the Modulo.Position you're telling the current lazy instance how many instances are simultaneously running (3.) and the position of which this instance is assigned to (.1) As an example for 3 lazyloggers running simultaneously the field assignment should be : 

 Channel    Field    Run#
 Lazy_1     3.0      21, 24, 27, ...
 Lazy_2     3.1      22, 25, 28, ...
 Lazy_3     3.2      23, 26, 29, ...

In the example above, the Modulo.Position is set to 2.1 , indicating this is instance 1, and two lazyloggers are running.


Tape Data Append

  • Type: BOOL
  • Default: "y"


If this key in the ODB /Lazy/<channel_name>/Settings subtree is set to "y", the spooling of the Tape device to the End_of_Device (EOD) before starting the lazy job is enabled. This command is valid only for Backup Type Tape. If this flag is not enabled the lazy job starts at the current tape position.


The ODB /Lazy/<channel_name>/Statistics subtree

The Statistics ODB subtree contains general information about the status of the current lazylogger channel.

An example of the Statistics subtree for a lazylogger channel is shown below:

[local:pol:S]/>ls /lazy/disk/Statistics/ Backup file 000321.mid File size (Bytes) 0 KBytes copied 0 Total Bytes copied 0 Copy progress (%) 0 Copy Rate (Bytes per s) 0 Backup status (%) 0 Number of Files 173 Current Lazy run 321


The ODB /Lazy/<channel_name>/List subtree

The List ODB subtree will contain arrays of run number associated with the array name backup-set label (see list label) . Any run number appearing in any of the arrays is considered to have been backed up.

An example of the List subtree for a lazylogger channel is shown below. In this case, the list label was set to "archive".

[local:pol:S]/>ls /lazy/disk/List archive 

                               230
                               231
                               232
                               233
                               234
                               235
                               236
                               237


Setting up the Lazylogger

The Lazylogger requires to be setup before data file can be moved. This setup consists of 4 steps:

Invoke the lazylogger once for setting up the appropriate ODB tree and exit. In this example, the channel is "Tape". 

 >lazylogger -c Tape

Edit the newly created ODB tree. Set the Settings field(s) to match your requirements. > odbedit -e midas [local:midas:Stopped]/>cd /Lazy/tape/ [local:midas:Stopped]tape>ls [local:midas:Stopped]tape>ls -lr Key name Type #Val Size Last Opn Mode Value

tape DIR 

   Settings                    DIR
       Maintain free space(%)  INT     1     4     3m   0   RWD  0
       Stay behind             INT     1     4     3m   0   RWD  -3
       Alarm Class             STRING  1     32    3m   0   RWD  
       Running condition       STRING  1     128   3m   0   RWD  ALWAYS
       Data dir                STRING  1     256   3m   0   RWD  /home/midas/online
       Data format             STRING  1     8     3m   0   RWD  MIDAS
       Filename format         STRING  1     128   3m   0   RWD  run%05d.mid
       Backup type             STRING  1     8     3m   0   RWD  Tape
       Execute after rewind    STRING  1     64    3m   0   RWD  
       Path                    STRING  1     128   3m   0   RWD  
       Capacity (Bytes)        FLOAT   1     4     3m   0   RWD  5e+09
       List label              STRING  1     128   3m   0   RWD  
   Statistics                  DIR
       Backup file             STRING  1     128   3m   0   RWD  none 
       File size [Bytes]       DOUBLE  1     4     3m   0   RWD  0
       KBytes copied           DOUBLE  1     4     3m   0   RWD  0
       Total Bytes copied      DOUBLE  1     4     3m   0   RWD  0
       Copy progress [%]       DOUBLE  1     4     3m   0   RWD  0
       Copy Rate [bytes per s] DOUBLE  1     4     3m   0   RWD  0
       Backup status [%]       DOUBLE  1     4     3m   0   RWD  0
       Number of Files         INT     1     4     3m   0   RWD  0
       Current Lazy run        INT     1     4     3m   0   RWD  0

[local:midas:Stopped]tape>cd Settings/ [local:midas:Stopped]Settings>set "Data dir" /data [local:midas:Stopped]Settings>set "Capacity (Bytes)" 15e9 Start lazylogger in the background >lazylogger -c Tape -D At this point, the lazylogger is running and waiting for the list label key to be defined before starting the copy procedure. The mstat utility will display information regarding the status of the lazylogger.

> odbedit -e midas [local:midas:Stopped]/>cd /Lazy/tape/Settings [local:midas:Stopped]Settings>set "List label" cni-043


Operation of the Lazylogger

For every major operation of the lazylogger a message is sent to the Message buffer and will be appended to the default MIDAS log file (midas.log). These messages are the only mean of finding out What/When/Where/How the lazylogger has operated on a data file. A fragment of the midas.log for the chaos experiment is shown below. In this case, the Maintain free space(%) field was enabled which produces the cleanup of the data files and the entry in the List tree after copy.

Fri Mar 24 14:40:08 2000 [Lazy_Tape] 8351 (rm:16050ms) /scr0/spring2000/run08351.ybs file REMOVED Fri Mar 24 14:40:08 2000 [Lazy_Tape] Tape run#8351 entry REMOVED Fri Mar 24 14:59:55 2000 [Logger] stopping run after having received 1200000 events Fri Mar 24 14:59:56 2000 [CHAOS] Run 8366 stopped Fri Mar 24 14:59:56 2000 [Logger] Run #8366 stopped Fri Mar 24 14:59:57 2000 [SUSI] saving info in run log Fri Mar 24 15:00:07 2000 [Logger] starting new run

Fri Mar 24 15:00:07 2000 [CHAOS] Run 8367 started Fri Mar 24 15:00:07 2000 [Logger] Run #8367 started Fri Mar 24 15:06:59 2000 [Lazy_Tape] cni-043[15] (cp:410.6s) /dev/nst0/run08365.ybs 864.020MB file NEW Fri Mar 24 15:07:35 2000 [Lazy_Tape] 8352 (rm:25854ms) /scr0/spring2000/run08352.ybs file REMOVED Fri Mar 24 15:07:35 2000 [Lazy_Tape] Tape run#8352 entry REMOVED Fri Mar 24 15:27:09 2000 [Lazy_Tape] 8353 (rm:23693ms) /scr0/spring2000/run08353.ybs file REMOVED Fri Mar 24 15:27:09 2000 [Lazy_Tape] Tape run#8353 entry REMOVED Fri Mar 24 15:33:22 2000 [Logger] stopping run after having received 1200000 events Fri Mar 24 15:33:22 2000 [CHAOS] Run 8367 stopped Fri Mar 24 15:33:23 2000 [Logger] Run #8367 stopped Fri Mar 24 15:33:24 2000 [SUSI] saving info in run log Fri Mar 24 15:33:33 2000 [Logger] starting new run Fri Mar 24 15:33:34 2000 [CHAOS] Run 8368 started Fri Mar 24 15:33:34 2000 [Logger] Run #8368 started Fri Mar 24 15:40:18 2000 [Lazy_Tape] cni-043[16] (cp:395.4s) /dev/nst0/run08366.ybs 857.677MB file NEW Fri Mar 24 15:50:15 2000 [Lazy_Tape] 8354 (rm:28867ms) /scr0/spring2000/run08354.ybs file REMOVED Fri Mar 24 15:50:15 2000 [Lazy_Tape] Tape run#8354 entry REMOVED ... Once the lazylogger has started a job on a data file, trying to terminate the application will result in producing a log message informing the user of the actual percentage of the backup completed so far. This message will repeat itself until completion of the backup, and only then the lazylogger application will terminate. If an interruption of the lazylogger is forced (kill...), the state of the backup device is undetermined. Recovery is not possible, and the full backup set has to be redone. In order to do this, you need: To rewind the backup device. Delete the /Lazy/<channel_name>/List/<list label> array. Restart the lazylogger with the -z switch which will "zap" the statistics entries. In order to facilitate the recovery procedure, lazylogger produces an ODB ASCII file of the lazy channel tree after completion of successful operation. This file (Tape_recover.odb) stored in Data dir can be used for ODB as well as lazylogger recovery.

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