qpid-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Alex Rudyy (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (QPID-7905) [Java Client AMQP 0-x] Connection#start is not thread-safe
Date Mon, 13 Nov 2017 16:02:00 GMT

    [ https://issues.apache.org/jira/browse/QPID-7905?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16249766#comment-16249766
] 

Alex Rudyy commented on QPID-7905:
----------------------------------

Whilst looking into the potential fix for the reported problem, the following approaches have
been analyzed:
* Adding synchronization locks into {{Connection#start}}/{{Connection#stop}} methods similar
to synchronization locks in {{Connection#close}}
* Moving sending of {{flow}} command into the dispatcher thread.

Adding synchronization locks would involve adding the following synchronization locks: session
creation lock, delivery lock, dispatcher lock and failover mutex.  Adding of these lock seem
would work for 0-9 code path. However, 0-10 path uses dispatcher thread to release pre-aquired
messages on {{Connection#stop}}, thus, acquisition of of delivery and dispatcher locks would
require changes to the code to release messages {{AMQSession#drainDispatchQueueWithDispatcher}}
which is called from {{AMQPSession_0_10#stop}}.

Moving sending of {{flow}} command into the dispatcher thread would require changes to how
dispatcher works. The dispatcher would need to be created and started immediately on {{Connection#start}}
and stopped on {{Connection#stop}} or started on  session creation if connection is started,
the code where flow is currently send (rollback/recover/SuspenderRunner/registerConsumer/start/stop)
would need to be changed to submit special tasks into dispatcher to send the flow. It seems
we need to make a lot of changes to the client in this case.




> [Java Client AMQP 0-x] Connection#start is not thread-safe
> ----------------------------------------------------------
>
>                 Key: QPID-7905
>                 URL: https://issues.apache.org/jira/browse/QPID-7905
>             Project: Qpid
>          Issue Type: Bug
>          Components: Java Client
>            Reporter: Lorenz Quack
>            Priority: Critical
>             Fix For: qpid-java-client-0-x-6.3.0
>
>
> The JMS spec says that Connections may be used from several threads concurrently.
> However, our implementation of {{Connection#start}} is currently not thread-safe. It
iterates over its list of sessions and calls {{Session#start}}. The session rightfully (this
is specified in the JMS spec as well) assumes that it is being called from a single thread.
> An example of the impact of this is that a session can be used (by {{Connection#start}})
after it has been closed (via {{Session#close}}) leading to an Exception due to the broker
receiving a frame with an unknown {{channelId}}.
> Note: The comment on {{Connection#start}} stating that JMS allows for non thread-safe
implementations seems to be in error!



--
This message was sent by Atlassian JIRA
(v6.4.14#64029)

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@qpid.apache.org
For additional commands, e-mail: dev-help@qpid.apache.org


Mime
View raw message