03610: | Container Lockup (due to reading from System.in) |
Category: Container
Status: ClosedSeverity: HIGHEST
Reported against release: 0.8
Fixed in release: 0.8.1 (Beta Refresh)
PROBLEM:The Container implementation sometimes locks up. This lockup occurs
most often during startup, but can happen later as well. This behavior
may have several different symptoms to the end user:
- The user gets "unable to install" messages from the shell
- The Hello world user panel freezes and won't go away (defect exists
for this problem)
The problem appears to occur when the container implementation or
processes running inside the container attempt to read from System.in. ANALYSIS:This problem occurs at different times on different platforms. Windows
2000 users often experience container lockup at startup.
Several Windows NT users have reported the Hello World User panel
freezing.
The Container program does some initialization on startup. Then it
prints out "Press any key to exit" and then blocks on System.in.read()
until it receives input, at which point it shuts down. This was a
debugging feature that was used during development to provide a clean
way to shut down a container that was started in a console window
The problem is that in the release, containers are started by the
container manager using Runtime.exec(). Because of how Runtime.exec()
handles the standard I/O streams, reading from standard in can
intermittently cause the container's JVM to hang. This explains the
nondeterministic behavior of this error and the fact that it varies
from platform to platform. For example, it appears that containers on
NT usually don't hang until the Hello World user program is started -
the second call to System.in.read().
The suggested solution is to eliminate the easy shutdown feature since
that is not how containers will be used in deployed systems.
In addition, the container needs a safeguard so that processes that run
inside it can't hang the container by reading from standard in.
Finally, the documentation on the website needs to be modified to
indicate that programs that run in containers may not read from
standard input. |
