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https://issues.apache.org/jira/browse/THRIFT-747?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tim Wilson-Brown updated THRIFT-747:
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Description:
If a Thrift C++ Client opens a TSocket, then calls fork(), the child process
can terminate the parent processes' connection by deleting its copy of the
parent TSocket.
In particular,
TSocket->close() calls shutdown(socket_,SHUT_RDWR) before close(socket_)
Discussion:
This behaviour is inconsistent, as it is:
* unlike the unix socket close() semantics - close() only affects the process
that calls it, and the socket is shut down when all copies of it are closed
* unlike the python and java code, which (appears) to only use close()
This design choice makes it really difficult to program a Thrift client that
forks other clients in C++, as the first process to call TSocket->close()
terminates all copies of the connection. The child process is unable to cleanup
its copy of the parent's connection - this is a particular issue when using
shared_ptr because the child process can not even exit().
However, the design choice also prevents deadlock/slowdown issues where a
forked process holds open a copy of the parent's Thrift connections.
The design choice may also be an attempt to implement the 'block to send then
close' behaviour described in
http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable
However, the shutdown call, and close with the default linger interval of 0 are
both hard resets.
In the absence of linger/shutdown, the kernel can usually send small thrift
messages by itself.
Options:
* The most functional resolution would be to implement
TSocket->setShutdownOnClose() that allows Thrift users to set their preference
for shutdown on socket close or delete. However, this change may also need to
be made to other language libraries.
* Removing shutdown() from TSocket->close() could break programs that expect
TSockets not to stay open if children are still running.
TODO:
* Confirm issue on Linux - see attached test code
* Decide how to resolve issue
* Create Patch - see attached TSocket.h & TSocket.cpp from Thrift 0.2.0 (I
don't know how to generate patches but I'm happy to try and work it out)
was:
If a Thrift C++ Client opens a TSocket, then calls fork(), the child process
can terminate the parent processes' connection by deleting its copy of the
parent TSocket.
In particular,
TSocket->close() calls shutdown(socket_,SHUT_RDWR) before close(socket_)
Discussion:
This behaviour is inconsistent, as it is:
* unlike the unix socket close() semantics - close() only affects the process
that calls it, and the socket is shut down when all copies of it are closed
* unlike the python and java code, which (appears) to only use close()
This design choice makes it really difficult to program a Thrift client that
forks other clients in C++, as the first process to call TSocket->close()
terminates all copies of the connection. The child process is unable to cleanup
its copy of the parent's connection - this is a particular issue when using
shared_ptr because the child process can not even exit().
However, the design choice also prevents deadlock/slowdown issues where a
forked process holds open a copy of the parent's Thrift connections.
Options:
* The most functional resolution would be to implement
TSocket->setShutdownOnClose() that allows Thrift users to set their preference
for shutdown on socket close or delete. However, this change may also need to
be made to other language libraries.
* Removing shutdown() from TSocket->close() could break programs that expect
TSockets not to stay open if children are still running.
TODO:
* Confirm issue on Linux - see attached test code
* Decide how to resolve issue
* Create Patch - see attached TSocket.h & TSocket.cpp from Thrift 0.2.0 (I
don't know how to generate patches but I'm happy to try and work it out)
Added notes about article at
http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable
describing reliable TCP communication
> C++ TSocket->close calls shutdown breaking forked parent process
> ----------------------------------------------------------------
>
> Key: THRIFT-747
> URL: https://issues.apache.org/jira/browse/THRIFT-747
> Project: Thrift
> Issue Type: Bug
> Components: Library (C++)
> Affects Versions: 0.2, 0.3
> Environment: Cygwin 1.7.1 on Windows XP SP3, Thrift 0.2.0 & r760184 &
> Trunk
> Reporter: Tim Wilson-Brown
> Priority: Minor
> Attachments: thrift_shutdown_example.cpp, TSocket-020-fix.cpp,
> TSocket-020-fix.h
>
> Original Estimate: 72h
> Remaining Estimate: 72h
>
> If a Thrift C++ Client opens a TSocket, then calls fork(), the child process
> can terminate the parent processes' connection by deleting its copy of the
> parent TSocket.
> In particular,
> TSocket->close() calls shutdown(socket_,SHUT_RDWR) before close(socket_)
> Discussion:
> This behaviour is inconsistent, as it is:
> * unlike the unix socket close() semantics - close() only affects the
> process that calls it, and the socket is shut down when all copies of it are
> closed
> * unlike the python and java code, which (appears) to only use close()
> This design choice makes it really difficult to program a Thrift client that
> forks other clients in C++, as the first process to call TSocket->close()
> terminates all copies of the connection. The child process is unable to
> cleanup its copy of the parent's connection - this is a particular issue when
> using shared_ptr because the child process can not even exit().
> However, the design choice also prevents deadlock/slowdown issues where a
> forked process holds open a copy of the parent's Thrift connections.
> The design choice may also be an attempt to implement the 'block to send then
> close' behaviour described in
> http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable
> However, the shutdown call, and close with the default linger interval of 0
> are both hard resets.
> In the absence of linger/shutdown, the kernel can usually send small thrift
> messages by itself.
> Options:
> * The most functional resolution would be to implement
> TSocket->setShutdownOnClose() that allows Thrift users to set their
> preference for shutdown on socket close or delete. However, this change may
> also need to be made to other language libraries.
> * Removing shutdown() from TSocket->close() could break programs that
> expect TSockets not to stay open if children are still running.
> TODO:
> * Confirm issue on Linux - see attached test code
> * Decide how to resolve issue
> * Create Patch - see attached TSocket.h & TSocket.cpp from Thrift 0.2.0 (I
> don't know how to generate patches but I'm happy to try and work it out)
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