Can no longer run phoebus at SNS because preference check limits the size of all preferences

[kasemir]

#3740 added this to take a snapshot of all settings in the Launcher:

Preferences.userRoot().put(SETTINGS_SNAPSHOT, prefsBuf.toString());

That bombs like this

java.lang.IllegalArgumentException: Value too long: # Preference settings<br/>
...
# End.<br/>
	at java.prefs/java.util.prefs.AbstractPreferences.put(AbstractPreferences.java:248)
	at org.phoebus.product.Launcher.loadSettings(Launcher.java:233)
	at org.phoebus.product.Launcher.main(Launcher.java:140)

because java.util.prefs.AbstractPreferences.put(AbstractPreferences.java:248) looks like this

   public void put(String key, String value) {
...
        if (value.length() > MAX_VALUE_LENGTH)
            throw new IllegalArgumentException("Value too long: "+value);
...

with a MAX_VALUE_LENGTH of

   /**
     * Maximum length of string allowed as a value (8192 characters).
     */
    public static final int MAX_VALUE_LENGTH = 8*1024;

[kasemir]

For what it's worth, prefsBuf.toString() has a size of 11782 in our case, but in general it's probably a bad idea to put a serialized snapshot of all settings into just one setting.

[kasemir]

Simply removing

Preferences.userRoot().put(SETTINGS_SNAPSHOT, prefsBuf.toString());

from the launcher allows phoebus to start up again.

[shroffk]

I think it might be cleaner to revert #3740
We will have to think of a better way to address the issue of how to filter the properties to be displayed in help.

@lcaouen can we brainstorm on this next Thursday and try to come up with a different solutions. I know this has been a tough nut to crack

[shroffk]

A potential idea would be to store the SETTINGS_SNAPSHOT not in the Preferences but maybe in a temporary file... not really a fan of this idea honestly

[lcaouen]

I think it might be cleaner to revert #3740 We will have to think of a better way to address the issue of how to filter the properties to be displayed in help.

@lcaouen can we brainstorm on this next Thursday and try to come up with a different solutions. I know this has been a tough nut to crack

Yes it's better to revert. This change only tried to avoid displaying "hard-coded" settings and not from settings.ini.
If we revert we keep the display in red in the about box whereas if you comment the code, the functionnality won't work anymore.

[lcaouen]

A potential idea would be to store the SETTINGS_SNAPSHOT not in the Preferences but maybe in a temporary file... not really a fan of this idea honestly

Not sure it's a good idea because you'll need to find a directory where you are sure Phoebus has the rights to write and which will work for any OS (Linux, Windows, Mac, ...).

We need to find a way to store the "orginal" settings in memory (just a String stored somewhere is enough) or a flag to say this setting is an "original" one and this one is a "hard-coded" one.

Let's brainstorm on Thursday