[jira] [Updated] (CONFIGURATION-532) FileChangedReloadingStrategy should support reloading of rolled-back (older timestamp) files

["Mike Lucas (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CONFIGURATION-532?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mike Lucas updated CONFIGURATION-532:
-------------------------------------

    Description: 
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}

  was:
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 the actual change is to use {{!=}} instead of {{>}} in the {{hasChanged}} method's comparison:
{code}
return file.lastModified() > lastModified;
{code}

    
> 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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