Matt,
We are running into similar issues with the 2.2 VFS jar running on
Accumulo 1.9.2 after upgrading from 1.8.1 but have been restarting
tservers to work around it and other issues with putting the iterators
in /tmp on certain systems.
In general though we love it because we can run multiple versions of
iterators on the same cluster and we have it deployed on several systems
with our clients for that specific use case.
Sean/Chris, if we rip it out would you imagine iterators being more like
HBase where you are basically bound to the startup classpath as the
baseline mechanism (with user-enabled specific class loaders). Or do you
imagine another upgrade/configuration mechanism? FYI we do VFS and the
general accumulo mechanism for configuring iterators and the iterator
api design because its pretty user/developer friendly.
Thanks,
Andrew
On 10/24/2018 10:55 PM, Christopher wrote:
The idea that Dave is talking about is that I don't think we should be
doing any classloader special sauce in accumulo-start at all, and we
might even be able to remove accumulo-start as a module entirely,
since this is its primary (sole?) purpose.
It's just a rough idea that I've tossed around with a few people, but
haven't really spent any time materializing it into a proposal, PR, or
experiment. Basically, I think we should rip out all classloader
special sauce. If a user still wishes to use a custom classloader for
any reason, using vfs2 or anything else, they can set a system class
loader with -Djava.system.class.loader=my.custom.CustomClassLoader
when they run java. This is an advanced Java option supported by Java
itself, and really shouldn't be a problem to punt this downstream.
Classloading is way outside the scope of what Accumulo does anyway,
and Accumulo should have its complexity centered around what it does,
and not "bells and whistles" on top of basic Java language functions.
If we wanted to, we could use our current classloading code to create
a classloader which could be used this way... and maybe provide it as
an example or explain it in a blog post. But, Accumulo shouldn't be
doing special sauce class loading... there are other projects that are
better suited to specializing that for any Java application... and
there's no reason we need it so tightly coupled to Accumulo.
Of course, there's still some utility in the per-table context
classloaders for pluggable components like iterators... and there's
probably room for improvement in the configuration of those... but the
main startup classloading is probably best to rip out.
I'm not sure if it should be done for 2.0 or not... maybe yes. I'd be
willing to rip it out... I enjoy ripping things out and reducing code
complexity. But, I don't really have a desire to do the work of
implementing or blogging about alternatives, if that's even necessary.
I'd hope that somebody else would do that, if they felt it was really
necessary once the built-in stuff was ripped out. For me, I'd be happy
mentioning the feature in the release notes, maybe linking to the docs
on the feature, and leaving implementation as an exercise for
downstream, with an open invitation for a guest blog on our website
about how it could be done.
I've been thinking we're probably going to want a second alpha... or a
beta, before 2.0 final... and if we did this for 2.0, I'd definitely
want another pre-release release first.
On Wed, Oct 24, 2018 at 3:10 PM Dave Marion <dmario...@gmail.com> wrote:
I have talked with Christopher about the VFS class loader in general and I
think he has a good approach. He can elaborate further if needed, but the
approach is to move it out of the core project and allow users to configure
it at runtime using the java.system.class.loader system property. There are
organizations using the VFSClassloader successfully, maybe it just needs to
be reimplemented.
On Wed, Oct 24, 2018 at 2:58 PM Sean Busbey <bus...@cloudera.com.invalid>
wrote:
sounds like a good DISCUSS thread for 2.0?
On Wed, Oct 24, 2018 at 1:43 PM Josh Elser <els...@apache.org> wrote:
It seems like commons-vfs2 is just a pile of crap.
It's been known to have bugs for years and we've seen zero progress from
them on making them better.
IMO, rip the whole damn thing out.
On 10/24/18 12:42 PM, Matthew Peterson wrote:
Hello Accumulo,
Summary: commons-vfs2 version 2.2 seems to have problems and it may be
worth rolling back to version 2.1 of commons-vfs2.
My project upgraded a system from Accumulo 1.8.1 to 1.9.2. Immediately
after switching vfs contexts we saw problems. The tservers would
error in
iterators about missing classes that were clearly on the classpath.
The
problems were persistent until we replaced the commons-vfs2.jar with
version 2.1 (Accumulo 1.9.2 uses version 2.2). Until we rolled vfs
back,
we received errors particularly with Spring code trying to access
various
classes and files within the jars. It looks like in 2.2, commons-vfs
implemented a doDetach method which closed the zip files. We suspect
that
code is the problem but haven't tested that theory.
I suspect that most users don't use this feature.
Thanks!
Matt
--
busbey
