Change in properties for logging: deliberate?

Jason Mehrens jason_mehrens at
Mon Nov 13 15:14:12 UTC 2017

Hi Daniel,

Sorry for the late reply I was offline for the long weekend.

Hot reloads of the LogManager have always been a problem.  I think you are running into in your testing and that is going to give you troubling results on what is recreated after the call.  Make sure you test updateConfiguration which is the replacement everyone is to use going forward.

I think you'll want to make it so that "handlers" is just an alias name ".handlers".  That way empty string is just name of the root logger which enables consistent use of other properties like ".level" and ".filter".
If both are defined in the, then install the union of the two lines.


From: Daniel Fuchs <daniel.fuchs at>
Sent: Friday, November 10, 2017 10:04 AM
To: Jason Mehrens; mandy chung
Cc: core-libs-dev at
Subject: Re: Change in properties for logging: deliberate?

Hi Jason,

I have done a few tests with JDK 8 & 7.

I have created custom handlers and added some
debug traces in their constructors and debug methods.

Then I have added these two lines to my

handlers = custom.Handler
.handlers = custom.DotHandler

What I see is this:

- the first time the configuration is read, two handlers
   are added to the root logger:
   - an instance of DotHandler (first), then an instance
     of Handler (second).

Then if you call LogManager.readConfiguration() again,
both handlers are closed, and this time only one
instance of Handler is added to the root logger.
No instance of DotHandler is added.
 From now on the property is ignored.

This is because the root logger is a special beast:
it will not be removed (like all other loggers) when
LogManager.readConfiguration() is called.

And as it happens, handlers are added to loggers
when the loggers are added to the LogManager.
As it happens, the ".handlers" property is only parsed
and read when the root logger is added to the LogManager,
and thus only once.

The "handlers" property on the other hand is parsed
every time LogManager.readConfiguration() is called.

Given that, I suspect we should deprecate the use of
".handlers" for the root logger, as it appears that
it has never worked properly. I could work on a patch
for 10 (possibly backport it to 9 update) to preserve
the strange behavior of 7 & 8, but is it worth it?

What are your thoughts?

best regards,

-- daniel

On 09/11/2017 19:50, Jason Mehrens wrote:
> Daniel,
> I would assume you would fix since it is advertised as a feature over here:
> If it helps, I've dug up a lot of the history on this over here a while back:
> I've updated that to include the links to this new issue.  Now that I've linked this message thread to that message thread that should crash the internet. :)
> Jason
> ________________________________________
> From: core-libs-dev <core-libs-dev-bounces at> on behalf of Daniel Fuchs <daniel.fuchs at>
> Sent: Thursday, November 9, 2017 1:29 PM
> To: mandy chung
> Cc: core-libs-dev at
> Subject: Re: Change in properties for logging: deliberate?
> On 09/11/2017 19:16, mandy chung wrote:
>> Daniel - we should add this known issue in the release note and document
>> the workaround.
> Hi Mandy,
> Right, it either need to be fixed, or documented in the release
> notes. Let me first have a look at the issue though.
> best regards,
> -- daniel

More information about the core-libs-dev mailing list