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https://issues.apache.org/jira/browse/HDFS-6254?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13980038#comment-13980038
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Chris Nauroth commented on HDFS-6254:
-------------------------------------
[~huangkx], thanks again for the code sample. I confirmed that the same
behavior happens for me: run the program directly and I get the expected
connection failure error, but run it under gdb and it dies with SIGSEGV.
I think the problem we're seeing is that the JVM actually traps SIGSEGV and
runs its own signal handler to attempt recovery. This is part of how the JVM
interacts with the kernel to manage memory. For example, see this code in
OpenJDK:
http://hg.openjdk.java.net/jdk6/jdk6/hotspot/file/tip/src/os/linux/vm/os_linux.cpp#l3873
gdb's own signal handling appears to be interfering with this and choosing to
suspend when it encounters a SIGSEGV. This doesn't really represent a bug in
the libhdfs code. In fact, if I resume execution after the SIGSEGV by using
the "fg" command, then it proceeds as expected, and I see the connection
failure.
If you don't want gdb to suspend when it sees a SIGSEGV, then another option is
to change its signal handling behavior by running this command:
{code}
(gdb) handle SIGSEGV nostop
{code}
BTW, I noticed a bug in the code sample you provided. It does not call
{{hdfsDisconnect}} on the allocated {{hdfsFS}} to free resources. This is
something that you'll want to add in your real code to avoid leaks. Also note
that the {{hdfsConnect}} function has been deprecated in favor of
{{hdfsBuilderConnect}}. For full details on this, refer to the hdfs.h header
file.
At this point, I'm going to resolve this issue, because this behavior does not
represent a bug in the libhdfs code. I hope this was helpful.
> hdfsConnect segment fault where namenode not connected
> ------------------------------------------------------
>
> Key: HDFS-6254
> URL: https://issues.apache.org/jira/browse/HDFS-6254
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: libhdfs
> Affects Versions: 2.2.0
> Environment: Linux Centos 64bit
> Reporter: huang ken
>
> When namenode is not started, the libhdfs client will cause segment fault
> while connecting.
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