RFR: 8043306 - Provide a replacement for the API that allowed to listen for LogManager configuration changes

[Daniel Fuchs]

On 9/12/14 5:39 PM, Jason Mehrens wrote:
> Daniel,
>
>
> I suppose that the propagating uncaught exceptions to the caller was the previous behavior of the old property change methods but it seems out of place for the LogManager.  The LogManager is a global resource so broken listener code in web app A could suppress notifications in web app B and C.  That doesn't seem very nice.  A lot of the LogManager code handles exception via catch, report or ignore, and continue when dealing with handlers etc.  I would think that same strategy applies here too.

Hi Jason,

Yes - that was also the behavior of the old property change methods.
When the global LogManager calls itself readConfiguration it will
silently ignore exceptions that might be raised.

I'm not too keen in specifying that exceptions raised by listeners will
be silently dropped. We're in the process of reinitializing the 
configuration,
so trying to log  the exceptions through a Logger would have its own
risks too.
Reporting exceptions raised during initialization and configuration is
an area where java.util.logging is clearly lacking.

For this patch - I think that our options are limited to the alternative:
   1. propagate the exception
   2. catch and silentlty drop the exception

What is the 'better' behavior (and I agree neither of the two are ideal)
probably depends on what is the typical use case for these listeners.
My assumption is that in most cases - there will be a single listener, in
which case 1. is probably better. I haven't seen any bug complaining
about how exceptions were handled in the previous implementation,
though I have seen some complaining about swallowed exceptions...

That said - if there is consensus that 2. is better - I have no real
objection except those stated above.

best regards,

-- daniel



>
>
>
> Jason
>
>
> ----------------------------------------
>> Date: Fri, 12 Sep 2014 16:59:03 +0200
>> From: daniel.fuchs at oracle.com
>> To: Alan.Bateman at oracle.com
>> Subject: Re: RFR: 8043306 - Provide a replacement for the API that allowed to listen for LogManager configuration changes
>> CC: core-libs-dev at openjdk.java.net
>>
>> On 9/12/14 4:42 PM, Alan Bateman wrote:
>>> On 12/09/2014 15:16, Daniel Fuchs wrote:
>>>> Thanks Alan!
>>>>
>>>> I have updated the webrev with your suggestions:
>>>>
>>>> http://cr.openjdk.java.net/~dfuchs/webrev_8043306/webrev.04/
>>>>
>>>> -- daniel
>>>>
>>> A minor suggestion for readConfiguration is that "Any register
>>> configuration listeners .." might be a bit better than "The
>>> configuration listeners ...".
>>>
>>> In addConfigurationListener there is a <br> between the two sentences
>>> that talk about exceptions, I don't know if you intended that.
>> Done. I regenerated the webrev in place.
>> http://cr.openjdk.java.net/~dfuchs/webrev_8043306/webrev.04/
>>
>> -- daniel
>>> Otherwise the javadoc looks good to me.
>>>
>>> -Alan.
>>