Shutdown hook complexities

[Bryan Duxbury]

I've been experiencing some problems in implementing a graceful  
shutdown in a server app I'm writing. The app keeps some HDFS files  
open at all times and needs to close them before completely shutting  
down. However, what keeps happening is that I get some "Filesystem  
closed" message.

I've tracked this down to the fact that Filesystem registers its own  
shutdown hook handler for the purpose of closing all filesystems.  
Apparently, this shutdown hook gets run prior to  (or concurrently  
with) my server shutdown hook, and as a result, when I try to close  
my files I can't.

I've looked around, and I can't seem to find a Java Runtime method  
for controlling the order of shutdown hooks, and I don't think HDFS  
gives me any way to suppress this shutdown hook behavior. Does it  
make sense for this to be configurable? I'd be fine with the  
responsibility of having to close all the filesystems myself as long  
as I got control.

-Bryan