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From Romain Manni-Bucau <rmannibu...@gmail.com>
Subject Re: [Math] Utilitzation of SLF4J?
Date Sun, 27 Sep 2015 02:05:29 GMT
Le 26 sept. 2015 15:19, "Ralph Goers" <ralph.goers@dslextreme.com> a écrit :
>
> Romain,
>
> Choosing JUL for a framework does a HUGE disservice to the users of your
framework. JUL is by far the worst logging framework design of anything you
could choose. It is like the JDK designers purposely chose to use a
mechanism to map their API to another implementation that really doesn’t
work.  SLF4J handles this by not bypassing it and using a JUL handler to
map everything into it, and then uses an “interesting” scheme to try to
make that perform well. Log4j tries to use the method documented by JUL but
it has a few problems.
>

It is contextual, slf4j with its classloader handling is the worse for
other users...all analyzis lead to a really "common" lib shouldnt rely on
any logging API IMHO.

> Ralph
>
> > On Sep 26, 2015, at 12:49 PM, Romain Manni-Bucau <rmannibucau@gmail.com>
wrote:
> >
> > Le 26 sept. 2015 12:07, "Luc Maisonobe" <luc@spaceroots.org <mailto:
luc@spaceroots.org>> a écrit :
> >>
> >> Le 26/09/2015 20:59, Ralph Goers a écrit :
> >>> I don’t normally participate in Math but I do feel the need to stick
my
> > nose in here.
> >>> 1. You are absolutely correct to determine whether you need logging at
> > all before discussing what to choose.
> >>> 2. If you do decide logging is required:
> >>>  a. Please stay away from java.util.logging. It really would be the
> > best solution for a framework like math except it is extremely
difficult to
> > redirect efficiently to some other logging framework. The methods used
by
> > SLF4J and Log4j are imperfect to say the least.
> >>>  b. Log4j 1.x has reached eol. It effectively has not been supported
> > for 5 years.
> >>>  c. Log4j 2 has an API that can be redirected to another logging
> > framework if desired.
> >>>  d. Commons logging still works but its API is very primitive by
> > todays standards. That said, it does work.
> >>
> >> From what I have seen, if I ever were to choose a logging framework for
> >> any project, I agree log4j 2 is currently the best choice. I was
> >> impressed by slf4j a few years ago, but think now the step further is
> >> log4j 2 (without any accurate reason, just a rough feeling).
> >>
> >
> > And in 2 years foolog4j will be better. JUL is not perfect for sure but
> > ensures:
> > - no dep
> > - always usable
> > - allows to let the user integrate with the lib without having to fork
it
> > to get rid of a logging dep - think to tomee which consumes N commons
deps,
> > if all uses a different logging framework it is worse to configure and
> > highly inconsistent - that is why we chose jul by default
> >
> > That is for the logging framework choice.
> > Now commons shouldnt log much IMO otherwise it would start to loose
commons
> > in sense of shareable component cause of the integration issues it
> > generates in the final application.
> >
> > - Romain
> >
> >> best regards,
> >> Luc
> >>
> >>>
> >>> Ralph
> >>>
> >>>
> >>>> On Sep 26, 2015, at 10:07 AM, Luc Maisonobe <luc@spaceroots.org>
wrote:
> >>>>
> >>>> Le 26/09/2015 18:42, Gilles a écrit :
> >>>>> On Sat, 26 Sep 2015 09:03:06 -0700, Phil Steitz wrote:
> >>>>>> On 9/26/15 4:56 AM, Thomas Neidhart wrote:
> >>>>>>> On 09/26/2015 01:11 PM, Gilles wrote:
> >>>>>>>> On Sat, 26 Sep 2015 09:53:30 +0200, Thomas Neidhart
wrote:
> >>>>>>>>> On 09/26/2015 02:33 AM, Gilles wrote:
> >>>>>>>>>> On Fri, 25 Sep 2015 16:52:26 -0700, Hasan Diwan
wrote:
> >>>>>>>>>>> On 25 September 2015 at 16:47, Gilles <
> > gilles@harfang.homelinux.org>
> >>>>>>>>>>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> On Fri, 25 Sep 2015 17:30:33 +0200,
Thomas Neidhart wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>>> On Fri, Sep 25, 2015 at 5:09 PM,
Gilles
> >>>>>>>>>>>>> <gilles@harfang.homelinux.org>
> >>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On Fri, 25 Sep 2015 07:28:48 -0700,
Phil Steitz wrote:
> >>>>>>>>>>>>>> On 9/25/15 7:03 AM, Gilles wrote:
> >>>>>>>>>>>>>>> On Fri, 25 Sep 2015 15:54:14
+0200, Thomas Neidhart wrote:
> >>>>>>>>>>>>>>>> Hi Ole,
> >>>>>>>>>>>>>>>>> for a start, I think
you are asking the wrong question.
> >>>>>>>>>>>>>>>>> First of all we
need to agree that we want to add some
> > kind of
> >>>>>>>>>>>>>>>>> logging
> >>>>>>>>>>>>>>>>> facility to CM.
> >>>>>>>>>>>>>>>>> If the outcome is
positive, there are a handful of
> >>>>>>>>>>>>>>>>> alternatives,
> >>>>>>>>>>>>>>>>> some of
> >>>>>>>>>>>>>>>>> them more viable
than slf4j in the context of CM (e.g.
> > JUL or
> >>>>>>>>>>>>>>>>> commons-logging).
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Could someone summarize
why those alternatives were
deemed
> >>>>>>>>>>>>>>>> "more
> >>>>>>>>>>>>>>>> viable"?
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> btw. the same discussion
has been done for other commons
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> components as
> >>>>>>>>>>>>>>>>> well, and the result
usually was: do not add logging
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> What was the rationale?
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Look at the archives.  We
have discussed this multiple
times
> >>>>>>>>>>>>>>> in the
> >>>>>>>>>>>>>>> past in [math] and each
time came to the conclusion that
> > Thomas
> >>>>>>>>>>>>>>> succinctly states above.
 What has changed now?
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>> We also discussed several times
to stick with Java 5.
> >>>>>>>>>>>>>> Fortunately, that has changed.
[Although sticking with Java
> > 7 is
> >>>>>>>>>>>>>> still
> >>>>>>>>>>>>>> a bad decision IMHO.]
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> As for logging, IIRC, the sole
argument was "no dependency"
> >>>>>>>>>>>>>> because
> >>>>>>>>>>>>>> (IIRC) of the potential "JAR
hell".
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>> that's not correct. The decision
to not include any
> >>>>>>>>>>>>> dependencies has
> >>>>>>>>>>>>> nothing to do with "JAR hell".
> >>>>>>>>>>>>>
> >>>>>>>>>>>> Although I can't find it now, I'm pretty
sure that I more
than
> > once
> >>>>>>>>>>>> got such an answer.
> >>>>>>>>>>>>
> >>>>>>>>>>>> In order to prevent JAR hell, commons
components strictly
stick
> >>>>>>>>>>>> to the
> >>>>>>>>>>>>> "Versioning guidelines" [1]
> >>>>>>>>>>>>>
> >>>>>>>>>>>> I can't see how it relates.
> >>>>>>>>>>>> But if you mean that no JAR hell can
emerge from using a
> > logging
> >>>>>>>>>>>> framework,
> >>>>>>>>>>>> then that's good news.
> >>>>>>>>>>>>
> >>>>>>>>>>>> The no-dependency rule is more related
to the proposal of the
> >>>>>>>>>>>> component,
> >>>>>>>>>>>>> see [2]
> >>>>>>>>>>>>>
> >>>>>>>>>>>> Thanks for the reminder; in that document,
we read:
> >>>>>>>>>>>>
> >>>>>>>>>>>> (1) Scope of the Package
> >>>>>>>>>>>>  [...]
> >>>>>>>>>>>>  5. Limited dependencies. No external
dependencies beyond
> > Commons
> >>>>>>>>>>>> components and the JDK
> >>>>>>>>>>>>
> >>>>>>>>>>>> So we are fine if use "Log4j 2" as kindly
offered by Gary.
> >>>>>>>>> log4j is not a commons component btw.
> >>>>>>>> Too bad for me. :-/
> >>>>>>>> Case resolved, then, by the argument of authority?
> >>>>>>> I just pointed out that log4j is not a commons component
and did
not
> >>>>>>> imply anything else.
> >>>>>>>
> >>>>>>>> "Commons" is OK but not another Apache project, by virtue
of a
> >>>>>>>> document that still refers to "JDK 1.2", "CVS", "Bugzilla"
(not
to
> >>>>>>>> mention that the "scope" of CM currently goes well beyond
"the
most
> >>>>>>>> common practical problems not immediately available
in the Java
> >>>>>>>> programming language")...
> >>>>>>>>
> >>>>>>>> What's the _technical_ rationale for accepting this
dependency
and
> >>>>>>>> not accepting that dependency?
> >>>>>>>>
> >>>>>>>>> I have not seen a single example of a useful logging
message
that
> >>>>>>>>> could
> >>>>>>>>> be added to commons-math, but we are already discussing
which
> >>>>>>>>> framework
> >>>>>>>>> to use.
> >>>>>>>> If it is not useful to you, why would you conclude that
it is not
> >>>>>>>> useful to others?
> >>>>>>>>
> >>>>>>>> At the cost of repeating myself, once more, the use-case
is not
> >>>>>>>> primarily about debugging CM, but sometimes one could
need to
> > assess
> >>>>>>>> how a "non-obvious" CM algorithm responds to an application's
> > request.
> >>>>>>>> I've clearly expressed that use-case in a previous message.
> >>>>>>>>
> >>>>>>>> Another example: I have a class that wraps a CM root
solver; it
is
> >>>>>>>> stuffed with log statements because the message contained
in the
> >>>>>>>> "NoBracketingException" was utterly insufficient (and
plainly
> >>>>>>>> misleading due the default formatting of numbers) to
figure out
why
> >>>>>>>> certain calls succeeded and others not.
> >>>>>>>> It's a problem (or a limitation) in the application,
but in the
> >>>>>>>> absence of other clues, tracing the solver could help
figure out
a
> >>>>>>>> workaround.
> >>>>>>>> The alternative to the "logging" approach, would have
been to
> > include
> >>>>>>>> a precondition check before calling the solver, that
would in
> > effect
> >>>>>>>> duplicate the bracketing check done inside the solver.
Given the
> > vast
> >>>>>>>> amount of cases where the code ran smoothly, this is
clearly a
> >>>>>>>> sub-optimal solution as compared to turning logging
on and rerun
> > the
> >>>>>>>> case that led to a crash.
> >>>>>>>>
> >>>>>>>> What can I say more about the usefulness (for a "low-tech"
person
> >>>>>>>> like me) than the intro here:
> >>>>>>>> http://logging.apache.org/log4j/2.x/manual/index.html
> >>>>>>>> ?
> >>>>>>>>
> >>>>>>>>> The examples with println debugging are not valid
imho, because
> > how do
> >>>>>>>>> you know in advance what you will need to log in
order to
> > successfully
> >>>>>>>>> debug some piece of code and such low-level information
should
> > not be
> >>>>>>>>> captured in logs anyway.
> >>>>>>>> Why are there several log levels?  Low-level info can
be routed
to
> >>>>>>>> "DEBUG" or "TRACE".
> >>>>>>>> As Ole put it quite eloquently, logging is a safety
net that we
> > hope
> >>>>>>>> we'll never need, until we do.
> >>>>>>>>
> >>>>>>>> Each layer of an application has its own notion of what
is the
> >>>>>>>> appropriate log level. What is "INFO" for some low-level
library
> >>>>>>>> will very probably not be so for most applications that
use the
> >>>>>>>> library.
> >>>>>>>> Setting levels per package or class takes care of that:
it's the
> >>>>>>>> library's *user* who chooses what is useful in the current
> > situation,
> >>>>>>>> not the library's developer.
> >>>>>>>> In the context of that asynchronous collaboration, the
role of
the
> >>>>>>>> library's developer is to carefully choose what *could*
be
> >>>>>>>> interesting, if the need should arise.
> >>>>>>>>
> >>>>>>>> So, can we eventually discuss the _technical_ arguments
against
> >>>>>>>> logging inside CM, rather than personal opinion?
> >>>>>>> again, what I want to see is an example what *should* be
logged in
> > the
> >>>>>>> case of an algorithm. Take the LevenbergMarquardtOptimizer
as an
> >>>>>>> example:
> >>>>>>>
> >>>>>>> * what did you log using System.out.println()?
> >>>>>>> * the algo computes a lot of internal data, which of these
is
> >>>>>>> interesting for debugging problems or for general logging?
> >>>>>>> * there are various branches the algo can take, are just
some
> >>>>>>> interesting to log, or all of them?
> >>>>>>>
> >>>>>>> the use-cases presented so far were mainly about debugging
specific
> >>>>>>> problems, and I am *strongly* against adding logging information
> > just
> >>>>>>> for this purpose as you are clearly facing a dilemma here:
> >>>>>>>
> >>>>>>> you have to log *everything* an algo does as otherwise you
might
> > miss
> >>>>>>> the part that creates problems
> >>>>>>>
> >>>>>>> but logging everything is not useful for a standard user
of the
> > library
> >>>>>>> so it contradicts the original proposal to include logging
> >>>>>>>
> >>>>>>> Again, CM is not an application where you need to log what
it is
> > doing,
> >>>>>>> but a bunch of algorithms and utility methods to perform
certain
> >>>>>>> calculations. I fail to see the need to add logging. What
could be
> >>>>>>> useful, and we had requests like that in the past, is to
observe
the
> >>>>>>> state of a certain algorithm and to decide how to proceed
in
certain
> >>>>>>> cases.
> >>>>>>>
> >>>>>>> That is useful for users.
> >>>>>>>
> >>>>>>> Another useful addition would be to add more aggressive
assertions.
> > If
> >>>>>>> one user encounters a problem, he/she could run the application
with
> >>>>>>> assertions enabled and spot potential problems e.g. due
to wrong
> > input.
> >>>>>>>
> >>>>>>> Logging is a solution for a non existing problem imho.
> >>>>>>> Logging will not avoid the need to debug CM in case of problems
> > imho.
> >>>>>>
> >>>>>> +1
> >>>>>> The other thing I would add is that the one place where it does
make
> >>>>>> sense to dump text is in exception error messages, which is
a place
> >>>>>> where I think we could really improve things.  Fortunately,
that is
> >>>>>> fairly easily done.
> >>>>>>
> >>>>>> I have seen nothing in this thread to convince me that adding
> >>>>>> logging in [math] will be net positive for either those of us
who
> >>>>>> maintain the component or for users.  If we are not providing
clear
> >>>>>> exception error messages and/or APIs (with complete documentation)
> >>>>>> so that users can understand what they need to debug their
> >>>>>> applications, then we should focus on solving those problems.
> >>>>>>
> >>>>>> Phil
> >>>>>
> >>>>> First, you carefully do not reply to any of the concrete arguments
> >>>>> given in this thread, second you give a conclusion to an issue not
> >>>>> reported in this thread: exceptions and logging do not provide the
> >>>>> same service.
> >>>>>
> >>>>> At least, I'd wish that people sharing their own opinion (it's
> >>>>> nothing more since _zero_ technical argument against logging have
> >>>>> been put forth) stop taking the collective "users" on their side.
> >>>>> As for *actual* users/maintainers, Ole and I have a need, while
> >>>>> Thomas and you haven't.  Those are all the facts that exist until
> >>>>> now.
> >>>>>
> >>>>> In such a situation, what do we do as a project; maintain the status
> >>>>> quo, or try for a change?
> >>>>> On numerous occasions over the years, the status quo was enforced;
> >>>>> and I don't see that it benefited the project in terms of new
> >>>>> contributors.
> >>>>> So I'm +1 for trying to change, for a change.
> >>>>
> >>>> I think one thing has been written in this thread that is worth
> >>>> noting and could be an intermediate position.
> >>>>
> >>>> It seems to me one place where we could get some useful information,
> >>>> and provide it to users is for iterative algorithms (both optimizers
> >>>> and solvers have already been mentioned, we could add ode integrators
> >>>> as well to this). For such algorithms, having some way to monitor how
> >>>> the iterations perform seem an improvement. An observer pattern as
> >>>> proposed a few days ago for this kind of algorithms would be fine.
> >>>> Once again, something simple and that does not attempt to be hyper
> >>>> generic but rather taylored to the algorithms (i.e. most probably
> >>>> different observer interfaces for different algorithms types).
> >>>>
> >>>> This intermediate position would provide something to both users
> >>>> and developers, and it would not attempt to log everything and
> >>>> add a dependency (I am probably the one who opposed to logging on
> >>>> the grounds of dependencies).
> >>>>
> >>>> best regards,
> >>>> Luc
> >>>>
> >>>>>
> >>>>>
> >>>>> Gilles
> >>>>>
> >>>>>>>
> >>>>>>> Thomas
> >>>>>>>
> >>>>>>>>>>>> My long-standing mentioning of slf4j
was only because of its
> >>>>>>>>>>>> "weightlessness" (thanks to the no-op
implementation of its
> > API).
> >>>>>>>>>>>> If "Log4j 2" has followed this path,
good for everyone.
> >>>>>>>>>>>>
> >>>>>>>>>>>> No objection, then?
> >>>>>>>>>>>
> >>>>>>>>>>> I'm still not clear what log4j 2 adds --
most Apache java
> > projects
> >>>>>>>>>>> seem to
> >>>>>>>>>>> use log4j 1.2, seems to work well. -- H
> >>>>>>>>>>>
> >>>>>>>>>> I can only answer about "slf4j" where the "f"
stands for
facade:
> > it's
> >>>>>>>>>> "only"
> >>>>>>>>>> an API, with bridges to several logging frameworks
(log4j,
> > logback,
> >>>>>>>>>> etc.).
> >>>>>>>>>>
> >>>>>>>>>> The separation of concerns (API vs one of several
> > implementations to
> >>>>>>>>>> choose from)
> >>>>>>>>>> allows the top-level application to uniformly
configure logging
> > or to
> >>>>>>>>>> disable it
> >>>>>>>>>> completely (if choosing the "no-op" implementation).
> >>>>>>>>> That is virtually true for all logging frameworks,
including
> > log4j,
> >>>>>>>>> slf4j, commons-logging.
> >>>>>>>> Has it always been true?
> >>>>>>>> I'm certainly no expert; I only try to stay clear of
tools about
> > which
> >>>>>>>> people complain a lot.  A few years ago, that was the
case of jcl
> > and
> >>>>>>>> jul as compared to slf4j.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Gilles
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> > ---------------------------------------------------------------------
> >>>>>>>> To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> >>>>>>>> For additional commands, e-mail: dev-help@commons.apache.org
> >>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> > ---------------------------------------------------------------------
> >>>>>>> To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> >>>>>>> For additional commands, e-mail: dev-help@commons.apache.org
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
---------------------------------------------------------------------
> >>>>>> To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> >>>>>> For additional commands, e-mail: dev-help@commons.apache.org
> >>>>>
> >>>>>
> >>>>>
---------------------------------------------------------------------
> >>>>> To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> >>>>> For additional commands, e-mail: dev-help@commons.apache.org
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>> ---------------------------------------------------------------------
> >>>> To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org <mailto:
> > dev-unsubscribe@commons.apache.org>
> >>>> For additional commands, e-mail: dev-help@commons.apache.org <mailto:
> > dev-help@commons.apache.org>
> >>>
> >>
> >>
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