Re: (Finally) Migrating from log4j 1.x

Gary,

On 12/17/21 22:18, Gary Gregory wrote:
> Log4j 2 can reconfigure itself when its configuration file changes by
> using the monitorInterval attribute, for example:
> 
> <Configuration name="ConfigTest" status="ERROR" monitorInterval="5">
> 
> See https://logging.apache.org/log4j/2.x/manual/configuration.html
> 
> For programmatic reconfiguration, you can use
> org.apache.logging.log4j.core.config.Configurator.
> 
> I hope that gives you a place to start.

I'll give it a shot. What we are doing is loading a default 
configuration (like "log to console") on startup and then, after reading 
a client-specific configuration file, applying that configuration to the 
already-initialized logging system. We can't predict the name of the 
config file at-or-before startup and we don't want to re-write the 
default configuration. I'm sure we can pass either a new file path to a 
Configurator and/or have it an in-memory configuration. We don't need to 
monkey-around with the in-memory Logger or Appender objects; just tell 
the logging system to reconfigure.

I have seen in the log4j debug logs that it knows how to "reconfigure" 
because it does it pretty much right away after loading. So I think I 
just need to tell it to reload again, but with a different set of configs.

Thanks,
-chris

> On Thu, Dec 16, 2021 at 11:02 AM Christopher Schultz
> <[email protected]> wrote:
>>
>> All,
>>
>> My understanding is that under many circumstances, migrating from log4j
>> 1.x -> 2.x is nearly as easy as simply upgrading the JAR file (and using
>> the migration bridge library), but there are some other restrictions as
>> noted here:
>>
>> https://logging.apache.org/log4j/2.x/manual/migration.html
>>
>> In various programs and services, we are using log4j 1.x in a way that
>> might be a little hacky. Specifically, we have a set of classes which
>> allow appenders and loggers to be reconfigured at runtime using calls
>> such as Appender(Skeleton).setThreshold. Is there a way to do this kind
>> of thing in log4j 2.x?
>>
>> We are also doing things like starting up with a hard-coded
>> configuration to print-to-console and then, after loading a
>> configuration from elsewhere (which may fail, hence logging to the
>> console), re-initialing the logging system, with the new setup (e.g. log
>> to file, network, etc.).
>>
>> The migration guide seems to say "you can't do this", but I think there
>> reality may be "you can't do it anymore.... in the same way".
>>
>> Can I get some practical tips for upgrading from log4j 1.x -> 2.x given
>> the desire to do some of the things listed above?
>>
>> Thanks,
>> -chris
>>
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