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https://issues.apache.org/jira/browse/TAP5-1287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12916993#action_12916993
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Howard M. Lewis Ship commented on TAP5-1287:
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Ah, the JMS is the critical issue.
What's happened is that the code change is observed by Tapestry and it discards
the current service instance.
However, because of what this service does (it obtains a JMS QueueSession, then
a Queue, then a MessageConsumer and then sets the consumer's message listener
to an inner class instance.
That's the trick: the service has exposed its implementation to the outside
world (the JMS code). The JMS code directly invokes methods on the service
implementation (or inner classes provided by the service implementation). Since
nothing is going through the proxy, the new version of the code is not reloaded.
Tapestry is missing a callback that would allow the existing service
implementation to cleanly shut down before being replaced.
I see this as an optional interface that could be implemented by a service
implementation (or, for that matter, an non-service proxy object):
public interface ReloadAware
{
void shutdownInstanceBeforeReload();
}
It might make sense to have a second method to alert the new instance that it
as been reloaded, but I'm not sure when that would be used, so I'll leave it
out for now. Further, I've given
some thought to services that have some internal state (such as a list of event
listener objects) that needs to persist between the old and new instances (i
picture a Map being passed to the old instance and then the new instance);
again, I'd rather play conservative and introduce a more complicated interface
that supports those features only as necessary.
> Services do not reload even though they should
> ----------------------------------------------
>
> Key: TAP5-1287
> URL: https://issues.apache.org/jira/browse/TAP5-1287
> Project: Tapestry 5
> Issue Type: Bug
> Components: tapestry-ioc
> Affects Versions: 5.2.2
> Reporter: Howard M. Lewis Ship
> Assignee: Howard M. Lewis Ship
>
> Been working on an application that uses a lot of JMS. I noticed that
> reloads did not appear to happen as expected.
> DEBUG MessageSinkSource - Invoking constructor public
> com.fivoosh.services.activemq.MessageSinkSourceImpl(org.slf4j.Logger,com.fivoosh.services.activemq.ActiveMQConnectionSource,org.apache.tapestry5.ioc.services.PerthreadManager,com.fivoosh.services.TimeService,java.util.Map).
> DEBUG MessageSinkSource - BEGIN Analyzing
> com.fivoosh.services.activemq.MessageSinkSourceImpl$1
> DEBUG MessageSinkSource - END Analyzing
> com.fivoosh.services.activemq.MessageSinkSourceImpl$1
> DEBUG MessageSinkSource - BEGIN Analyzing
> com.fivoosh.services.activemq.MessageSinkSourceImpl$TextQueueSender
> DEBUG MessageSinkSource - END Analyzing
> com.fivoosh.services.activemq.MessageSinkSourceImpl$TextQueueSender
> DEBUG MasterMessageHandler - Processing message
> 'ID:Howards-Mighty-Tool.local-56885-1285896586008-3:0:9:1:1' from queue 'echo'
> Message received on thread ActiveMQ Session Task:
> {
> "foo" : "bar"
> }
> I then changed the code (it affects the logging message that starts
> "Processing message ....":
> DEBUG MasterMessageHandler - Implementation class
> com.fivoosh.services.activemq.MasterMessageHandlerImpl has changed and will
> be reloaded on next use.
> DEBUG MasterMessageHandler - Processing message
> 'ID:Howards-Mighty-Tool.local-56885-1285896586008-3:0:10:1:1' from queue
> 'echo'
> Message received on thread ActiveMQ Session Task:
> {
> "foo" : "bar"
> }
> Note that the message indicates the implementation class changed, but the old
> behavior is stuck.
> Later changes to the code and new messages sent:
> DEBUG MasterMessageHandler - Processing message
> 'ID:Howards-Mighty-Tool.local-56885-1285896586008-3:0:12:1:1' from queue
> 'echo'
> Message received on thread ActiveMQ Session Task:
> {
> "foo" : "baz"
> }
> ... do not even register that a change occured.
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