[ https://issues.apache.org/jira/browse/THRIFT-748?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
James E. King, III closed THRIFT-748. ------------------------------------- Resolution: Won't Fix Assignee: James E. King, III In light of the resolution of THRIFT-747, I am resolving this issue the same way. > 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: C++ - Library > 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 > Assignee: James E. King, III > Priority: Trivial > Attachments: thrift_linger_example.cpp > > 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 behaviour is identical to the behaviour of unix sockets when SO_LINGER > is set (implementations vary). > However, the SO_LINGER default for sockets is off not on. This provides > unexpected behaviour in TSocket. > 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) or (1,timeout) 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. > 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 default linger interval of 0 turns the linger setting into a > hard reset. > And in the absence of linger, the kernel can usually send small thrift > messages by itself. > Options: > * Change the default lingerOn to 0 - rely on the kernel to resend a limited > number of times > * Change the default lingerVal to > 0 > - a large value like INT_MAX would match the default connection, send, > and recv 'no timeout' behaviour > TODO: > * Confirm issue on Linux - see attached test code > * Decide if a change to the defaults is needed > * Document workaround after resolution of [#THRIFT-747] - call > TSocket->setLinger(0,0) or (1,timeout) if forking -- This message was sent by Atlassian JIRA (v7.6.3#76005)