The following comment has been added to this issue:
Author: David Farb
Created: Tue, 12 Oct 2004 1:47 PM
Body:
In the typical 'Command' pattern, the knowledge (code) to execute the command
is inside the command object. In Craig's terms, in the special packet that
percolates through the system. You could think of Craig's packet as a
'Command'.
The problem I was refering to was encapsulating that much knowledge inside this
'failure command'. Consider an HTTP server to an EJB server, to some database
connectors, ... Passing a single failure command through all of these objects,
and having each of them be told how to fail with the logic inside the 'failure
command' object seems like too much to ask from the failure command class. It
needs to know about ALL the possible classes in the server, or all the classes
in the server need to implement the same interface (eg. the Failure
interface...).
Using Craig's approach distributes the logic about how to fail into each of the
packet processors, while using the 'fail()' method approach removes the if
(packet instanceOf ...) (or what ever) logic in the packet processors. The
'fail()' method has the advantage of making the contract explicit.
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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 1:47 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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