
Omniscient Debugging - jamesjyu
http://www.lambdacs.com/debugger/
======
klibertp
From the page:

"Everybody loves it! They clearly understand the concept. They ask great
questions, they make suggestions. But do they use it afterwards??

The ODB is as close to a silver bullet as you can get. Why don't people use
it?

I don't get it. :-("

"Needed

More than anything else, I need people to use the ODB."

Now, this tool is not for me personally - I don't see myself writing for JVM
anytime soon - but it seems really good. I wanted to ask you, as the author is
asking, why don't you, Java and other JVM programmers, use this tool?

Is it that there are better tools? You're not allowed to use this? You don't
think it is worth it? The tool itself proved to be somehow lacking? Or are you
actually using it heavily and the page is outdated?

I know nothing about Java ecosystem, Java programming or about ODB - I just
felt that, if what the author writes is true, it's truly sad situation and
would like to know why it happened.

~~~
drostie
Feedback -- not of the 'comments and criticism' variety.

Think of any successful project like a nuclear chain reaction. If you are not
familiar with nuclei, some of them are "too heavy" and want to fall apart,
spraying neutrons everywhere; they especially do this when they get absorb an
extra neutron flying around, but quantum mechanics always gives you a spare
neutron eventually.

The system transitions from negative feedback (no chain reaction) to positive
feedback (chain reaction) according to a very simple principle: the number of
free neutrons that a free neutron creates (call it N) must be more than one.
(N=1 is the replacement rate; it's a metastable state of reaction. If you
like, the reason why some nuclear reactors have been risky is that horrible
accidents kill the safeguards which are simply designed to force N ≤ 1.)

This principle is so fundamental -- it's why there's a 'meme' analogue to the
'genes' in the modern theory of evolution, why countries become bureaucracies,
and why nuclear reactors are hard -- that I hope everyone working in startups
starts thinking about their products this way. It's not _signups_ which you
need to have a successful product. It's that every free customer must convert,
on average, greater than or equal to one new free customer. Even if you cannot
get all the way to one, you boost your marketing effects by a factor of 1/(1 -
N), so if you can increase N from converting 0.25 people per person to 0.30
people per person, it's as good as spending 10% more on marketing.

And it applies, yes, to any open-source project too. The open-source projects
which succeed are those which help hackers to help those projects, just like
the genes which succeed are the ones which help their species to spread that
gene. I'm not even sure that this particular project is open-source. (I
believe it falls into a special case where the GPL is used as a closed-source
license. That is, GPL requires me to provide a copy of the source code when I
distribute the code -- but I do not have the source code, and I cannot coerce
the author into giving it to me, so I am not actually free to distribute the
binary either until they give me permission to do so one way or another.) The
author's claimed reason for not providing a way to "Fork me on GitHub" is, "I
have not made a major effort to put its code on any of the open source
repositories as it does not currently seem the right thing to do. Just not
worth the effort." And that's probably the deepest reason why it's fallen into
neglect.

~~~
klibertp
Yes, I found this bit about not setting up a public repository strange, too,
but the reason there is no "Fork me on GitHub" seems to be just that the
project predates Github by a year :)

You're hinting at licensing as (one of) a reason that this project was
abandoned, but I think the author just wasn't sure what to do with his code -
I think he wanted to get some money out of the project and didn't know or
couldn't decide how to do it. If enough users told him they wanted the source,
I think he would comply - it's just that there never was enough users (seems
so).

Your analysis is interesting and a good one (thanks!), but it doesn't answer
the more fundamental question: why the project failed to get another user out
from every user it already had? That's assuming somebody was actually using
ODB - maybe it failed at even lower level: everyone said it's cool and stuff,
but nobody really gave it a chance and actually started using it.

I'd like to know which one it is and why? If something like this was available
for Python (btw: is there something similar?) I think I would use it instead
of ipdb without hesitation (assuming that I would know about it).

From what the author writes he did his best to inform the Java world about his
and his project existence. So why aren't we all using this and similar tools
today?

I think this can be an interesting case for every developer who wants to
change something with his software. This debugger failed; LightTable seems to
have a high chance of succeeding - what's the difference between them? (Not
having Bret Victor talks as an inspiration seems an obvious one :))

------
onan_barbarian
Very cool. A C/C++ version (also mildly abandoned around the same time) was
done by Robert O'Callahan, a very smart guy...

Worth checking out and it would be nice if someone could pick it up and
develop it more actively.

<http://code.google.com/p/chronomancer/>

~~~
wladimir
_"The Chronicle framework provides complete register and memory-level
recording of Linux processes and efficient queries over the recorded traces."_

Wow, I was looking for something __exactly __like this a while ago, but was
unable to find it. I notice that these days with Google it's really hard to
find a tool or project when you're looking for it especially if it's more
obscure. Might be a consequence of the ranking rules that crowd lesser known
pages out.

~~~
wladimir
BTW I looked around a bit and found another similar system, based on QEMU
instead of Valgrind, claiming to be faster, ie less runtime overhead while
tracing, and also supporting kernel mode:
<http://wiki.nss.cs.ubc.ca/Tralfamadore>

Edit: never mind, the program does not seem to be publicly available, just
papers

------
pron
I occasionally use the omniscient debugger to debug some particularly tricky
bugs, and it's always proved quite useful.

There is also a more modern-looking, commercial implementation of the same
concept, but I've never used it: <http://www.chrononsystems.com/>

------
ced
_you don't have to wonder which threads ran when_

How does that work? Does it really record every single assignment to every
variable in every thread? Wouldn't that potentially slow everything down
sufficiently that some classes of multithreaded bugs wouldn't show up under
ODB?

------
mtoader
Interesting concept (one that i actually stumbled upon a couple of years ago).

If i would venture to guess why people don't use it more often i would say
that it's because the marginal win (ease of debugging for a certain class of
hard bugs) is smaller then the hassle of changing the complete toolset
(current debugger and tools).

My guess this kind of tool is really good at a small class of hard bugs (which
in general are pretty rare). For all the other the current tools are good
enough so a switch would be costly for no immediate gain.

------
arikrak
How does this compare with the tools mentioned here:
<http://stackoverflow.com/a/4561350/388928>

------
nkerkin
I believe Visual Studio 201x Intellitrace feature is very similar, it "lets
developers step back in time to see what happened in an application without
having to restart the debugger".

[http://msdn.microsoft.com/en-
us/library/vstudio/dd264915.asp...](http://msdn.microsoft.com/en-
us/library/vstudio/dd264915.aspx)

------
ghratch
There is an open-source (but Linux only) project called FReD which does
reversible debugging for C and C++ programs: <https://github.com/fred-
dbg/fred>

It works without modifying the program (e.g. no recompilation step necessary)
or the debugger (like gdb).

------
greenyoda
Looks like this page is from 2007 and the latest version of the debugger works
with Java 1.5.

~~~
pron
I don't think I've tried it with Java 7, but it works just fine with Java 6.

------
sur
The OCaml debugger also has time travel
([http://caml.inria.fr/pub/docs/manual-
ocaml-4.00/manual030.ht...](http://caml.inria.fr/pub/docs/manual-
ocaml-4.00/manual030.html)).

------
alexpopescu
Such an advanced debugger would make me miss the hours spent debugging a bug
just to jump over and/or press the wrong key on the line of code revealing the
real problem. That'd be unacceptable.

------
pdeva1
Try Chronon. While Omniscent is a research project, Chronon is a full blown
product <http://www.chrononsystems.com/>

