On 08/14/2012 05:09 PM, Adam Litke wrote:
On Mon, Aug 13, 2012 at 04:54:18PM -0400, Ayal Baron wrote:
----- Original Message -----
----- Original Message -----
From: "Yaniv Kaul" <[email protected]>
To: "Adam Litke" <[email protected]>
Cc: [email protected]
Sent: Monday, August 13, 2012 11:49:21 AM
Subject: Re: Consumability of vdsm via libvdsm.so
On 08/13/2012 06:21 PM, Adam Litke wrote:
Hi all,
We just finished a lively discussion regarding the ongoing effort
to
stabilize
the vdsm API using a C library called libvdsm. There are many
things
that need
discussion, but I would like to focus this thread on one in
particular:
Can ovirt-engine consume libvdsm via JNI?
libvdsm provides a full-featured C interface to the vdsm API using
GObject.
Java bindings are provided automatically by jGIR[1]. The library
communicates
with vdsmd using an internal transport which is not exposed to end
users
(including ovirt-engine). I would like to learn from folks with
deep
Java
knowledge if this approach is workable. What are the technical
challenges to
integrating in this way? Please save discussion of AMQP and other
bindings for
other threads.
Thanks!
[1] https://live.gnome.org/JGIR
How mature/maintained is JGIR?
Last commit seems to be 2010-02-09.
The author is: Alexander Kurtakov <[email protected]>
His status in our organizational chart:
Employee Type: Ex-employee
It will need some work to get it up to par with the rest of the
gobject generators
It's been dead since 2009, that doesn't seem very promising
(http://www.ohloh.net/p/java-gobject-introspection)
It also states: "It also includes a custom GLib/GObject interface layer adapted from
gstreamer-java." and looking at gstreamer-java yields: "An unofficial/alternative set of
java bindings for the gstreamer multimedia framework"
Again, doesn't look like something you want to base your API on.
Sounds to me like the 'free' java bindings come at a very high cost (bringing
JGIR up to date and maintaining it).
What are the alternatives?
Hi Adam,
Bare in mind that invoking JNI from Java EE violates Java EE spec.
In addition, if you have a bug at your library (i.e - you build some
abstraction layer library above some C API in order to simplify calls
that will be made from java code) - this bug may cause segmentation
fault, which will cause your JVM to crash -> meaning your jboss
application server will crash.
I know we only run the engine enterprise application on Jboss (although
an application server can co-host several application servers - in this
case, your penalty will be higher).
What I've seen in some enterprise application is a light java server
serving an application server to invoke risky/native code.
You of course pay for the traffic between the application server and
this "jni server" but at least you guarantee your application server
does not crash.
These are my 2 cents on this subject
Yair
There are two other alternatives (and one bad idea) that come to mind:
1.) Generate our own Java bindings to libvdsm.so during the vdsm build process.
I prefer this option from an API cleanliness POV because the transport code
would only be written once (in libvdsm.so). This form of generation should be
simple because we are just wrapping the library so it can be called via JNI.
2.) Generate a native Java "library" that is equivalent to libvdsm.so.
This gets us into the business of libvirt-style bindings generation which I
think is a mistake. It opens the door to us maintaining parallel
implementations of "libvdsm"s (one per language).
-1.) Standardize the transport around JSON-RPC and make that the supported
interface.
I am only mentioning it because I am certain someone will bring it up. I think
it's a bad idea and it's off-topic for this particular thread anyway.
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