[jira] [Created] (FELIX-4195) Sync on a Preference doesn't do a OS side sync

["Matt Wiselka (JIRA)" <ji...@apache.org>]

Matt Wiselka created FELIX-4195:
-----------------------------------

             Summary: Sync on a Preference doesn't do a OS side sync
                 Key: FELIX-4195
                 URL: https://issues.apache.org/jira/browse/FELIX-4195
             Project: Felix
          Issue Type: Bug
          Components: Preferences Service
    Affects Versions: prefs-1.0.6
         Environment: Anstroem Embedded Linux
UBIFS on a flash drive
            Reporter: Matt Wiselka


I ran in to the following problem using the Preferences Service on an embedded device with a flash memory:
When a preference is changed the sync method is called to persist it. A sudden power loss occurs. On restart the preference file in the bundle cache is empty and causes a BackingStoreException: Could not load preference.

It seems to me as that the OS is caching the write to the flash drive and the change is not actually persisted. I was able to fix this issue by performing a sync on the FileDescriptor of the OutputStream in the store method of the DataFileBackingStoreImpl

{code}
        try {
            final FileOutputStream os = (FileOutputStream) this.getOutputStream(root.getDescription());
            this.write(root, os);
            os.getFD().sync();
            os.close();
        }
        catch (IOException ioe) {
            throw new BackingStoreException("Unable to store preferences.", ioe);
        }
{code}

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