[Quickfixj-users] A deadlock while using the SSL

[Alexander G. <ago...@ac...>]

Hello all!

I am using the quickfix/j 1.1.0 to communicate with the FIX counterparty =
using the SSL connection. And the application periodically freezes which =
makes it impossible to use it in the production. I investigated the code =
and the problem lies in the implementation of the code synchronization =
for the org.apache.mina.filter.SSLFilter and the quickfix.Session. The =
code in these classes is synchronised by the current SSLHandler instance =
and the current Session instance respectively. And since the filter =
chain goes from one filter to another without releasing the lock, there =
is a high probability for an application to run into a deadlock.=20

That's what happened with my application. Below are the stack traces of =
the reading and the writing threads that caused the deadlock with my =
comments:

// 1. The reading thread:=20

quickfix.Session.getDataDictionary(Session.java:1649) <--- attempt to =
acquire the Session lock which is held by the writing thread [deadlock]
quickfix.mina.AbstractIoHandler.messageReceived(AbstractIoHandler.java:11=
1)
org.apache.mina.common.support.AbstractIoFilterChain$TailFilter.messageRe=
ceived(AbstractIoFilterChain.java:705)
org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageRecei=
ved(AbstractIoFilterChain.java:362)
org.apache.mina.common.support.AbstractIoFilterChain.access$5(AbstractIoF=
ilterChain.java:356)
org.apache.mina.common.support.AbstractIoFilterChain$1.messageReceived(Ab=
stractIoFilterChain.java:802)
org.apache.mina.filter.codec.support.SimpleProtocolDecoderOutput.flush(Si=
mpleProtocolDecoderOutput.java:60)
org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(Protocol=
CodecFilter.java:184)
org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageRecei=
ved(AbstractIoFilterChain.java:362)
org.apache.mina.common.support.AbstractIoFilterChain.access$5(AbstractIoF=
ilterChain.java:356)
org.apache.mina.common.support.AbstractIoFilterChain$1.messageReceived(Ab=
stractIoFilterChain.java:802)
org.apache.mina.filter.SSLFilter.handleAppDataRead(SSLFilter.java:627)
org.apache.mina.filter.SSLFilter.handleSSLData(SSLFilter.java:605)
org.apache.mina.filter.SSLFilter.messageReceived(SSLFilter.java:395) =
<--- acquisition of the SSLHandler lock

...

// 2. The writing thread:

org.apache.mina.filter.SSLFilter.filterWrite(SSLFilter.java:456) <--- =
attempt to acquire the SSLHandler lock which is held by the reading =
thread [deadlock]
org.apache.mina.common.support.AbstractIoFilterChain.callPreviousFilterWr=
ite(AbstractIoFilterChain.java:447)
org.apache.mina.common.support.AbstractIoFilterChain.access$8(AbstractIoF=
ilterChain.java:440)
org.apache.mina.common.support.AbstractIoFilterChain$1.filterWrite(Abstra=
ctIoFilterChain.java:826)
org.apache.mina.filter.codec.ProtocolCodecFilter$ProtocolEncoderOutputImp=
l.doFlush(ProtocolCodecFilter.java:403)
org.apache.mina.filter.codec.support.SimpleProtocolEncoderOutput.flush(Si=
mpleProtocolEncoderOutput.java:110)
org.apache.mina.filter.codec.ProtocolCodecFilter.filterWrite(ProtocolCode=
cFilter.java:220)
org.apache.mina.common.support.AbstractIoFilterChain.callPreviousFilterWr=
ite(AbstractIoFilterChain.java:447)
org.apache.mina.common.support.AbstractIoFilterChain.access$8(AbstractIoF=
ilterChain.java:440)
org.apache.mina.common.support.AbstractIoFilterChain$1.filterWrite(Abstra=
ctIoFilterChain.java:826)
org.apache.mina.common.support.AbstractIoFilterChain$TailFilter.filterWri=
te(AbstractIoFilterChain.java:729)
org.apache.mina.common.support.AbstractIoFilterChain.callPreviousFilterWr=
ite(AbstractIoFilterChain.java:447)
org.apache.mina.common.support.AbstractIoFilterChain.fireFilterWrite(Abst=
ractIoFilterChain.java:437)
org.apache.mina.transport.socket.nio.SocketSessionImpl.write0(SocketSessi=
onImpl.java:191)
org.apache.mina.common.support.BaseIoSession.write(BaseIoSession.java:145=
)
org.apache.mina.common.support.BaseIoSession.write(BaseIoSession.java:131=
)
quickfix.mina.IoSessionResponder.send(IoSessionResponder.java:38)
quickfix.Session.send(Session.java:1627)
quickfix.Session.sendRaw(Session.java:1576) <--- acquisition of the =
Session lock
...

As far as I can see, there is a high probability of having similar =
deadlocks in other parts of the filter chain when using the SSLFilter. =
The problem can be solved by changing the synchronization model for the =
quickfix.Session class. I understand though that this task is rather =
complex and time consuming. Do you see other ways of solving this? =
Please advise, I am willing to contribute if necessary.

Thank you,
Alexander Gorbachev.