Not able to open selector in solaris for non root user

Question

I have a server application which runs fine in most of the cases but in one solaris machine it not able to open the selector ,for root user it is working fine. for other user it is giving the below exception

java.io.IOException: Permission denied
at sun.nio.ch.DevPollArrayWrapper.init(Native Method)
at sun.nio.ch.DevPollArrayWrapper.<init>(DevPollArrayWrapper.java:74)
at sun.nio.ch.DevPollSelectorImpl.<init>(DevPollSelectorImpl.java:54)
     at sun.nio.ch.DevPollSelectorProvider.openSelector(DevPollSelectorProvider.java:18)
at java.nio.channels.Selector.open(Selector.java:209)

any suggestions on this.

Answer 1

In the absence of a more comprehensive error message from the native wrapper, use truss to identify the low-level system call which fails (most probably with EACCES), while running as the non-root user:

truss -l -d -f -vall -wall -o truss.out java ... TestOrAppClass

What you expect to see in truss.out after the Java application throws the exception and terminates (or is terminated) -- note the interleaved spaces in I O E x c e p t i o n:

...
...
...
...
23515/1:         0.2912 some_system_call(params)                        Err#13 EACCES [ALL]
...
23515/1:         0.2923 write(2, 0x08044F84, 39)                        = 39
23515/1:           j a v a . i o . I O E x c e p t i o n :   P e r m i s s i o n
23515/1:           d e n i e d
...
...
...
...

If the application in question is too complex and generates too much output (or is otherwise difficult to invoke from the command line), then write and compile a small test class which reproduces the problem by calling java.nio.channels.Selector.open() directly.

If you do not/cannot write a simple test class then remember that you can always use the extra output logged by the -wall option to correlate the time (and thread/LWP) at which the stack trace printout was produced with the actual system call, which should have failed shortly before.

In the sample truss.out output above, 23515 is the process ID, /1 is the LWP ID (doubling as "thread" identifier if the JVM uses native threads, which it almost certainly does on Solaris), 0.2912 is the timestamp (seconds since java process/trace startup), and some_system_call failing with EACCES is the call of interest.

What version of the JDK are you using?