[daisy] [JIRA] Commented: (DSY-664) lost data with unsuccessful backup?

[Karel Vervaeke]

On Fri, 2008-07-04 at 15:44 +0200, Wolfram Mayer (JIRA) wrote:
> [ http://issues.cocoondev.org//browse/DSY-664?page=comments#action_13667 ] 
> 
> Wolfram Mayer commented on DSY-664:
> -----------------------------------
> 
> "Backups never lead to changed data. A restore obviously does change data, but if I interpret your report, no restore was ever made? "
> ==> Sure, the backup didn't change data. At that date document editing should have changed data, but hasn't.

During backups, the repository is locked and you should not be able to
make any changes.  

a) If you save during a backup I would expect the user to receive an
error message
b) if your are editing and behind the scenes a backup starts and
finishes, you should be able to save and your data should be changed.

Since you mention a failed backup, there must be more involved.

> 
> "That's worrying, are you saying that there are changes to the blobstore backup file but not to the other backup files (especially the db backup file(s))? "
> ==> No. All blobstore backups contained these changes but this was not visible in the UI.

The changes ended up in the backup, but they did not show up in the
frontend?  That's very strange.

> " Do you mean unsuccesful? If there was a one-time failure I would not worry, perhaps it was just a full disk, java vm crash or some other random glitch. "
> ==> No. I mean suceesful. We had only 1 incidence when the backup failed. After that date all backups were succesful, but changed data from that date wasn't visible in the UI.
> 
> "Backup locks are taken at the beginning of a backup and released at the end of the backup - it should not make any difference if the backup fails or succeeds."
> ==> But how will it unlock if a backup fails? Could it happen that after a crashed backup there is still a lock?

The code is structured as follows (roughly)

try {
  lock()
  dobackup()
} finally {
  unlock()
}

This ensures that no matter what happens during the backup, the
backuplock will always be taken away after a backup.

> "That sentence just does not make sense. What do you mean with " "which is not recognized?". When there is a backup lock you can not make any changes to the repository"
> ==> I meant: is it possible that a backup lock remains and no changes can be done for documents (only reads)?

It seems unlikely.
Are there any relevant logfiles you could find?

Karel