The following comment has been added to this issue:
Author: David Farb
Created: Tue, 12 Oct 2004 12:51 PM
Body:
An explicit contract would be a better solution than the packet approach in my
opinion, as Craig said: 'The teardown signal object got special handling at
each level, which actually was a disadvantage, since it required an "if"
statement to check the type of signal object, ...'.
This type of situation is better handled with an explicit method such as
fail(), reserved for that use. Then both the normal method (sendUp) and the
failure method (fail) are simpler. I would add the exception (if any) to the
fail method just for documentation purposes:
public void fail(Throwable throwable);
Once the fail 'signal' gets to the top of the protocol stack, other means such
as custom wrapper objects can be used to percolate the information to other
parts of the server.
The 'Command' pattern seems like it ought to fit here, but the number of
different classes of server objects looks like a problem.
As far as I can tell, I may be the only one using this code at the moment, so I
would be happy to build the fix. I will probably wait until next week to allow
more time for feedback and comment.
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View this comment:
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View the issue:
http://issues.apache.org/jira/browse/GERONIMO-373
Here is an overview of the issue:
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Key: GERONIMO-373
Summary: Percolate errors from SocketProtocol up the stack
Type: Improvement
Status: Unassigned
Priority: Major
Project: Apache Geronimo
Components:
general
Assignee:
Reporter: David Farb
Created: Tue, 12 Oct 2004 9:42 AM
Updated: Tue, 12 Oct 2004 12:51 PM
Environment: All environments
Description:
o.a.g.network.protocol.SocketProtocol does not percolate a client error or
exception up the protocol stack when the client disconnects.
When serviceRead in SocketProtocol gets an IOException or some other error, the
socketChannel is closed, but the up protocol is not informed.
Calling the teardown method of the up protocol is probably not an appropriate
way to handle these exceptions. The teardown method should be called by the
creator of the protocol stack. Instead, the exception/error should percolate up
the protocol stack to the creator (via some sort of callback mechanism) which
should then remove the stack and associated information from the server
environment.
Either a new method reserved for this could be defined in the Protocol
interface (up.handleException(Throwable t)) or sending a null, empty or
specially marked packet via up.sendUp(UpPacket upPacket) could be implemented.
Since in most cases the server is waiting for a client response, if the client
goes away, server components need to be informed of this fact so the server
side objects can be cleaned up. There is usually no way to recover these
objects, hence they are a memory leak.
I would be happy to submit a fix for this, but I would appreciate feedback on
the most appropriate way to do it.
Thanks
David Farb
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