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https://issues.apache.org/jira/browse/THRIFT-748?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tim Wilson-Brown updated THRIFT-748:
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Description:
If a Thrift C++ Client opens a TSocket, writes some data, then calls fork(),
the child process can terminate the parent processes' connection by deleting
its copy of the parent TSocket.
In particular,
the default setting of lingerOn_ = 1 causes a RST to be sent in close(socket_)
in TSocket->close()
Discussion:
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 processes all have to call
TSocket->setLinger(0,0) before deleting the TSocket, closing the TSocket, or
exiting. (This workaround only succeeds with the suggested fix in [#THRIFT-747]
).
However, the design choice also prevents deadlock/slowdown issues where a
forked process holds open a copy of the parent's Thrift connections. It also
makes close non-blocking, which is ideal in a destructor.
Options:
Do we want to change the default? What is linger useful for?
TODO:
* Confirm issue on Linux - see attached test code
* Decide if a code change is needed
* Document workaround after resolution of [#THRIFT-747] - call
TSocket->setLinger(0,0) if forking
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)
Priority: Trivial (was: Minor)
Edited clone of [#THRIFT-747] for linger issue
> C++ TSocket default linger setting breaks forked parent process
> ---------------------------------------------------------------
>
> Key: THRIFT-748
> URL: https://issues.apache.org/jira/browse/THRIFT-748
> 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: Trivial
> Original Estimate: 72h
> Remaining Estimate: 72h
>
> If a Thrift C++ Client opens a TSocket, writes some data, then calls fork(),
> the child process can terminate the parent processes' connection by deleting
> its copy of the parent TSocket.
> In particular,
> the default setting of lingerOn_ = 1 causes a RST to be sent in
> close(socket_) in TSocket->close()
> Discussion:
> 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 processes all have to call
> TSocket->setLinger(0,0) before deleting the TSocket, closing the TSocket, or
> exiting. (This workaround only succeeds with the suggested fix in
> [#THRIFT-747] ).
> However, the design choice also prevents deadlock/slowdown issues where a
> forked process holds open a copy of the parent's Thrift connections. It also
> makes close non-blocking, which is ideal in a destructor.
> Options:
> Do we want to change the default? What is linger useful for?
> TODO:
> * Confirm issue on Linux - see attached test code
> * Decide if a code change is needed
> * Document workaround after resolution of [#THRIFT-747] - call
> TSocket->setLinger(0,0) if forking
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