Hello Bruno.
On Sun, 12 Aug 2018 08:56:37 +0000 (UTC), Bruno P. Kinoshita wrote:
Hi all,
I commented on IMAGING-154, but copying the last comment here as it
contains the approach I would like to follow to fix the last change
in
the project blocking
a 1.0 release:
---
So went ahead to re-design the Debug class, in a way users could
still enable/disable debugging, and also use a PrintStream so that
other thing rather than System.out could be used.
Then, realized removing System.out was the natural next step. But
alas, the library uses System.out for debugging, but sometimes it
uses
it for writing to System.out in a "verbose mode". What is more
complicated, is that sometimes classes methods like `toString()` are
calling debug methods that receive a PrintStream already.
So I spent some more time quickly comparing what other libraries I've
seen being used / or used for image processing:
https://kinoshita.eti.br/2018/08/12/use-of-logging-in-java-image-processing-libraries/.
Turns out only very low level libraries, such as the JNI bridge for
OpenCV, im4java, and Java's ImageIO can do with just throwing
Exception's.
All other libraries have one way or another of logging. Be it with
JUL, SLF4J, custom loggers, or with the ol' System.out/err.
My preferred compromise for this ticket was to keep Debug, making
System.out possible but optional, and mark the class internal only.
Now my preferred solution is to keep the Debug internal, but add a
logger to it. And then also add logging to replace where System.out
is
used for the "verbose" mode.
---
Any thoughts? Objections? If none, I will try to work on this issue
next weekend, making the Debug class internal only, and replacing
System.out by a logging utility. After that, we should be good to
start preparing the vote for 1.0.
* I know it's hard to get a consensus on having logging in Commons
components, as we have normally low level libraries, where using
logging is not always practical.
There are Log4j2 experts reading here. It would be interesting
to hear them about what is practical or not. There are several
aspects to "practical": simplicity, flexibility, compatibility,
performance, ...
How does Log4j2 fare in these areas?
Is there a known (through experience) limit in where it should
be used?
But I would now argue that Java own
ImageIO is low level. But ImageJ2, Processing, OpenJPEG, and Commons
Imaging are located at a higher level, some times even using it for
basic image handling/parsing/reading.
As with many discussions on this list, conflicting arguments occur
because people lack common (!) definitions.
So one goes: "You cannot do <something> in a low-level component"
but does not define "low-level"...
* Feel free to cast a counter-argument for it, but please think
whether you'd still be -0, +0 for this change. We have delayed 1.0
for
a while, so if you have a strong opinion on not adding a logger,
please provide an alternative for IMAGING-154.
Otherwise we may fail
to prepare a 1.0 release yet again, and then somebody else may have
to
work on it in a few months/years...
We are there because the project is too rigid about itself as
a whole (cf. for example the [RNG] thread about BC).
IMHO, it's not the always least common denominator that is the
best decision...
As you noticed, components most easily stall in their development
for lack of proper review, or risk acceptance (i.e. assume that
those who are closer to the code (at a given time) probably know
best... :-/
My opinion is that we can take the risk to introduce logging, and
if people complain somehow, take it back later.
one possible compromise for this,
might be i) make Debug internal,
+1
[Hmm... Does "internal" mean that minor release can break BC
on such a class?]
ii) remove all System.out calls,
+1 or
-1
[Depends on what "low-level" means here. "stdout"/"stderr" is
indeed used in low-level utilities but is the intent the same
here?]
which means removing the verbose flags, the checks, and calls to
System.out in there.
It would be a loss of potentially useful information (e.g. for
debugging).
Regards,
Gilles
Thanks!
Bruno
________________________________
From: Bruno P. Kinoshita <brunodepau...@yahoo.com.br.INVALID>
To: Commons Developers List <dev@commons.apache.org>
Sent: Tuesday, 6 February 2018 11:30 PM
Subject: Re: [imaging] IMAGING-154 remove Debug class
Hi sebb,
Another aspect of debugging is ensuring that methods are small and
easily tested independently.
However this is difficult to do, and care must be taken to ensure
that
the public API is not unnecessarily extended..
A very good point.
The parsers in commons-imaging expose some #dump... methods
(https://github.com/apache/commons-imaging/blob/7e7f96857df999175bb614732e13272a82f7962a/src/main/java/org/apache/commons/imaging/ImageParser.java#L794).
While I can see that parsers may need to dump the data they are
holding in some structured way for inspecting, reporting,
serializing,
etc, it looks like some other classes were affected by it too. For
example...
A JPEG Segment has a #dump() method
https://github.com/apache/commons-imaging/blob/7e7f96857df999175bb614732e13272a82f7962a/src/main/java/org/apache/commons/imaging/formats/jpeg/segments/Segment.java#L34
which gets defined in each subclass of Segment. It can be confusing
to have a method such as #dump() in a Segment, from the point of view
of someone writing a photo editor for example. The user could use
that
to pass his/her own logger's PrintWriter, which would make removing
or
changing logging in the future in commons-imaging.
If we keep the Debug class, and make it internal, there would still
be these methods to take care. And there are some methods where users
can provide a PrintWriter, while others instead use System.out
(e.g.https://github.com/apache/commons-imaging/blob/7e7f96857df999175bb614732e13272a82f7962a/src/main/java/org/apache/commons/imaging/FormatCompliance.java#L70).
Cheers
Bruno
________________________________
From: sebb <seb...@gmail.com>
To: Commons Developers List <dev@commons.apache.org>; Bruno P.
Kinoshita <brunodepau...@yahoo.com.br>
Sent: Tuesday, 6 February 2018 11:06 PM
Subject: Re: [imaging] IMAGING-154 remove Debug class
On 6 February 2018 at 09:52, Bruno P. Kinoshita
<brunodepau...@yahoo.com.br.invalid> wrote:
Hi Jorg,
I'd be fine with that solution too. I think this one would cause the
smaller change to the code as is.
I believe my preference is still to remove the Debug class. But
between logging and making Debug internal only, I'd choose making it
internal.
+1
I think making it internal means it can still be dropped later.
Looking forward to hearing what others think about these options.
Another aspect of debugging is ensuring that methods are small and
easily tested independently.
However this is difficult to do, and care must be taken to ensure
that
the public API is not unnecessarily extended..
Thanks
Bruno
________________________________
From: Jörg Schaible <joerg.schai...@bpm-inspire.com>
To: dev@commons.apache.org
Sent: Tuesday, 6 February 2018 9:24 PM
Subject: Re: [imaging] IMAGING-154 remove Debug class
Hi Bruno,
if it might also be helpful to our users, why not keep and provide
it. As
I understand it, the Debug class is a tool helping in development to
analyze some behavior.
Nothing stops us from declaring this class internal (we might even
put it
into a package "internal" or "debug") that might be changed without
further comment. Nobody may rely on it in production code, but
during
development it might be helpful. With such an approach we might not
have
a need to find a better interface to provide this functionality.
Just my 2¢,
Jörg
Am Mon, 05 Feb 2018 12:20:58 +0000 schrieb Bruno P. Kinoshita:
Hello,
If memory serves me well, some time ago we had a discussion around
sanselan & commons-imaging 1.0. One of the issues with
commons-imaging
1.0 was the Debug class.
https://issues.apache.org/jira/browse/IMAGING-154
I finished the pull request, but Gilles raised an important point,
about
discussing other alternatives first.
Initially I am against logging in low level libraries, especially
commons components. But some time ago I had to debug TIFF issues in
commons-imaging, and having the dump methods was a tremendous help.
The issue is that some imaging algorithms/processing have a lot of
variables that can be altered. And keeping an eye on all of them in
the
debugger can be quite hard - though not impossible.
So all in all, now I am more confident to proceed without the Debug
class. But some users could have a hard time investigating possible
issues in the library without seeing what's going on within the
library.
IMO, that could be solved with the logging/dump features... or
through a
better design, especially around exception handling/throwing. The
latter
is my preferred approach. Instead of logging, I prefer - whenever
possible - that low level libraries throw exceptions and let me
handle
the logging.
So, any thoughts? :) I'm +1 to remove the Debug class, and +0 to a
logging added to commons-imaging.
Bruno
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