Package CedarBackup2 :: Package actions :: Module store
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Module CedarBackup2.actions.store

Implements the standard 'store' action.
Authors:
Kenneth J. Pronovici <pronovic@ieee.org>, Dmitry Rutsky <rutsky@inbox.ru>
Function Summary
  executeStore(configPath, options, config)
Executes the store backup action.
  writeImage(config, newDisc, stagingDirs)
Builds and writes an ISO image containing the indicated stage directories.
  writeStoreIndicator(config, stagingDirs)
Writes a store indicator file into staging directories.
  consistencyCheck(config, stagingDirs)
Runs a consistency check against media in the backup device.
  writeImageBlankSafe(config, rebuildMedia, todayIsStart, blankBehavior, stagingDirs)
Builds and writes an ISO image containing the indicated stage directories.

Variable Summary
Logger logger = <logging.Logger instance at 0x4032a6ec>

Function Details

executeStore(configPath, options, config)

Executes the store backup action.
Parameters:
configPath - Path to configuration file on disk.
           (type=String representing a path on disk.)
options - Program command-line options.
           (type=Options object.)
config - Program configuration.
           (type=Config object.)
Raises:
ValueError - Under many generic error conditions
IOError - If there are problems reading or writing files.

Notes:

  • The rebuild action and the store action are very similar. The main difference is that while store only stores a single day's staging directory, the rebuild action operates on multiple staging directories.
  • When the store action is complete, we will write a store indicator to the daily staging directory we used, so it's obvious that the store action has completed.

writeImage(config, newDisc, stagingDirs)

Builds and writes an ISO image containing the indicated stage directories.

The generated image will contain each of the staging directories listed in stagingDirs. The directories will be placed into the image at the root by date, so staging directory /opt/stage/2005/02/10 will be placed into the disc at /2005/02/10.
Parameters:
config - Config object.
newDisc - Indicates whether the disc should be re-initialized
stagingDirs - Dictionary mapping directory path to date suffix.
Raises:
ValueError - Under many generic error conditions
IOError - If there is a problem writing the image to disc.

Note: This function is implemented in terms of writeImageBlankSafe. The newDisc flag is passed in for both rebuildMedia and todayIsStart.

writeStoreIndicator(config, stagingDirs)

Writes a store indicator file into staging directories.

The store indicator is written into each of the staging directories when either a store or rebuild action has written the staging directory to disc.
Parameters:
config - Config object.
stagingDirs - Dictionary mapping directory path to date suffix.

consistencyCheck(config, stagingDirs)

Runs a consistency check against media in the backup device.

It seems that sometimes, it's possible to create a corrupted multisession disc (i.e. one that cannot be read) although no errors were encountered while writing the disc. This consistency check makes sure that the data read from disc matches the data that was used to create the disc.

The function mounts the device at a temporary mount point in the working directory, and then compares the indicated staging directories in the staging directory and on the media. The comparison is done via functionality in filesystem.py.

If no exceptions are thrown, there were no problems with the consistency check. A positive confirmation of "no problems" is also written to the log with info priority.
Parameters:
config - Config object.
stagingDirs - Dictionary mapping directory path to date suffix.
Raises:
ValueError - If the two directories are not equivalent.
IOError - If there is a problem working with the media.

Warning: The implementation of this function is very UNIX-specific.

writeImageBlankSafe(config, rebuildMedia, todayIsStart, blankBehavior, stagingDirs)

Builds and writes an ISO image containing the indicated stage directories.

The generated image will contain each of the staging directories listed in stagingDirs. The directories will be placed into the image at the root by date, so staging directory /opt/stage/2005/02/10 will be placed into the disc at /2005/02/10. The media will always be written with a media label specific to Cedar Backup.

This function is similar to writeImage, but tries to implement a smarter blanking strategy.

First, the media is always blanked if the rebuildMedia flag is true. Then, if rebuildMedia is false, blanking behavior and todayIsStart come into effect:
  If no blanking behavior is specified, and it is the start of the week,
  the disc will be blanked

  If blanking behavior is specified, and either the blank mode is "daily"
  or the blank mode is "weekly" and it is the start of the week, then 
  the disc will be blanked if it looks like the weekly backup will not
  fit onto the media.

  Otherwise, the disc will not be blanked
How do we decide whether the weekly backup will fit onto the media? That is what the blanking factor is used for. The following formula is used:
  will backup fit? = (bytes available / (1 + bytes required) <= blankFactor
The blanking factor will vary from setup to setup, and will probably require some experimentation to get it right.
Parameters:
config - Config object.
rebuildMedia - Indicates whether media should be rebuilt
todayIsStart - Indicates whether today is the starting day of the week
blankBehavior - Blank behavior from configuration, or None to use default behavior
stagingDirs - Dictionary mapping directory path to date suffix.
Raises:
ValueError - Under many generic error conditions
IOError - If there is a problem writing the image to disc.

Variable Details

logger

Type:
Logger
Value:
<logging.Logger instance at 0x4032a6ec>                                

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