Hi Dmitry,
On 11/12/2014 15:43, Dmitry Samersoff wrote:
Jaroslav,
You can set SO_LINGER to zero, in this case socket will be closed
immediately without waiting in TIME_WAIT
SO-LINGER did not help either in my case (see my previous mail to Jaroslav).
That ended-up in using another hard-coded (supposedly free) port.
Note that was before RMI tests used randomly allocated ports.
But there are no reliable way to predict whether you can take this port
or not after you close it.
This is what I observed in my case.
So the only valid solution is to try to connect to a random port and if
this attempt fails try another random port. Everything else will cause
more or less frequent intermittent failures.
IIRC think this is what is currently done in RMI tests.
Olivier.
On 2014-12-11 17:06, Jaroslav Bachorik wrote:
On 12/09/2014 01:25 PM, Jaroslav Bachorik wrote:
On 12/09/2014 01:39 AM, Stuart Marks wrote:
On 12/8/14 12:35 PM, Jaroslav Bachorik wrote:
Please, review the following test change
Issue : https://bugs.openjdk.java.net/browse/JDK-8066708
Webrev: http://cr.openjdk.java.net/~jbachorik/8066708/webrev.00
The test fails very intermittently when RMI registry is trying to bind
to a port
previously used in the test (via ServerSocket).
This seems to be caused by the sockets created via `new
ServerSocket(0)` and
being in reusable mode. The fix attempts to prevent this by explicitly
forbidding the reusable mode.
Hi Jaroslav,
I happened to see this fly by, and there are (I think) some similar
issues going on in the RMI tests.
But first I'll note that I don't think setReuseAddress() will have the
effect that you want. Typically it's set to true before binding a
socket, so that a subsequent bind operation will succeed even if the
address/port is already in use. ServerSockets created with new
ServerSocket(0) are already bound, and I'm not sure what calling
setReuseAddress(false) will do on such sockets. The spec says behavior
is undefined, but my bet is that it does nothing.
I guess it doesn't hurt to try this out to see if it makes a difference,
but I don't have much confidence it will help.
The potential similarity to the RMI tests is exemplified by JDK-8049202
(sorry, this bug report isn't open) but briefly this tests the RMI
registry as follows:
1. Opens port 1099 using new ServerSocket(1099) [1099 is the default
RMI registry port] in order to ensure that 1099 isn't in use by
something else already;
2. If this succeeds, it immediately closes the ServerSocket.
3. Then it creates a new RMI registry on port 1099.
In principle, this should succeed, yet it fails around 10% of the time
on some systems. The error is "port already in use". My best theory is
that even though the socket has just been closed by a user program, the
kernel has to run the socket through some of the socket states such as
FIN_WAIT_1, FIN_WAIT_2, or CLOSING before the socket is actually closed
and is available for reuse. If a program -- even the same one --
attempts to open a socket on the same port before the socket has reached
its final state, it will get an "already in use error".
If this is true I don't believe that setting SO_REUSEADDR will work if
the socket is in one of these final states. (I remember reading this
somewhere but I'm not sure where at the moment. I can try to dig it up
if there is interest.)
I admit this is just a theory and I'm open to alternatives, and I'm also
open to hearing about ways to deal with this problem.
Could something similar be going on with this JMX test?
Hm, this is exactly what happened with this test :(
The problem is that the port is reported as available while it is still
occupied and RMI registry attempts to start using that port.
If setting SO_REUSEADDR does not work then the only solution would be to
retry the test case when this exception occurs.
Further investigation shows that the problem was rather the client
connecting to a socket being shut down.
It sounds like setting SO_REUSEADDR to false should prevent this failure.
From the ServerSocket javadoc:
"When a TCP connection is closed the connection may remain in a timeout
state for a period of time after the connection is closed (typically
known as the TIME_WAIT state or 2MSL wait state). For applications using
a well known socket address or port it may not be possible to bind a
socket to the required SocketAddress if there is a connection in the
timeout state involving the socket address or port."
It also turns out that the test does not close the server sockets
properly so there might be several sockets being opened or timed out
dangling around.
I've updated the test so it is setting SO_REUSEADDR for all the new
ServerSockets instances + introduced the mechanism to run the test code
while properly cleaning up any allocated ports.
http://cr.openjdk.java.net/~jbachorik/8066708/webrev.01/
-JB-
-JB-
s'marks
