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From "Oliver Heger (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CONFIGURATION-532) FileChangedReloadingStrategy should support reloading of rolled-back (older timestamp) files
Date Wed, 13 Mar 2013 21:10:13 GMT

    [ https://issues.apache.org/jira/browse/CONFIGURATION-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13601640#comment-13601640
] 

Oliver Heger commented on CONFIGURATION-532:
--------------------------------------------

Your request perfectly makes sense to me. The documentation of {{FileChangedReloadingStrategy}}
says
{quote}
A reloading strategy that will reload the configuration every time its underlying file is
changed.
{quote}
So one could argue that the current behavior to detect only newer files is actually a bug.
I think when the class was created the author had the assumption that somehow modifying the
configuration file would always result in a newer timestamp which is obviously not the case.

So shouldn't we in general use a != comparison?
                
> FileChangedReloadingStrategy should support reloading of rolled-back (older timestamp)
files
> --------------------------------------------------------------------------------------------
>
>                 Key: CONFIGURATION-532
>                 URL: https://issues.apache.org/jira/browse/CONFIGURATION-532
>             Project: Commons Configuration
>          Issue Type: Improvement
>          Components: File reloading
>    Affects Versions: 1.9
>            Reporter: Mike Lucas
>   Original Estimate: 48h
>  Remaining Estimate: 48h
>
> Currently the {{FileChangedReloadingStrategy}} only reloads when the timestamp of the
file on the filesystem is _newer_ than the timestamp it had when it was last loaded.
> This may not be the expected behaviour when, for example, an administrator makes a backup
copy of the original configuration file before making changes. If the administrator wants
to roll back to the original configuration, he may expect that copying/renaming the backup
back to the original name, would cause the original configuration to take effect again.
> Another example where the current behaviour is problematic is when using a Deploy System
(like we do at my company). We expect to be able to roll-back to a previous configuration
by simply redeploying the Config artifact, but because the timestamps reflect when the Config
artifact was _built_ (not when it was deployed), this roll-back will not work.
> The current behaviour could be kept as the default, simply adding {{setReloadOnRollback()}}
or similarly named method to change the behaviour to reload when the timestamp is either older
or newer (i.e. not equal to) the {{lastModified}} variable. Another option would to be to
create subclass {{FileChangedOrRolledBackReloadingStrategy}} that overrides the {{hasChanged()}}
method.
> In either option the actual change is to use {{!=}} instead of {{>}} in the {{hasChanged}}
method's comparison:
> {code}
> return file.lastModified() > lastModified;
> {code}

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