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From "Stephane Ramet (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ATLAS-992) Added support for message queue properties an Selectors in Apache.NMS.MSMQ
Date Wed, 06 Jul 2016 09:24:11 GMT
Stephane Ramet created ATLAS-992:
------------------------------------

             Summary: Added support for message queue properties an Selectors in Apache.NMS.MSMQ
                 Key: ATLAS-992
                 URL: https://issues.apache.org/jira/browse/ATLAS-992
             Project: Atlas
          Issue Type: Improvement
            Reporter: Stephane Ramet
         Attachments: 2016-07-05 - Apache.NMS.MSMQ.patch

The proposed package implements the following enhancements :

1. Support for communication of message properties between compatible peers
The DefaultMessageConverter has been enhanced, so as to marshall custom message properties
in the MSMQ Message.Extension field, along with the NMSCorrelationID which was already marshalled
in this field.
An additional flag specifies whether the MSMQ Message.Label field should be populated with
the NMSType (as currently - default value) or with the value of a message property called
"Label".

2. Support for selectors
A parser for selection strings has been introduced.
It is based on the Apache.ActiveMQ V4 implementation, ported from Java to C#.
MessageReaders have been developped, that support various types of filtering:
- no filtering when no selector strings are specified.
- filtering based on the Id (NMSMessageID), CorrelationId (NMSCorrelationID) or LookupId properties.
- filtering based on any other valid selection string.
MessageReaders have been introduced in MessageConsumers and QueueBrowsers.

The generic filtering system, based on a selection string, has - at least - two limitations:
- it cannot be fully included in the build chains: the source code is generated from SelectorParser.csc
(a port of ActiveMQ's SelectorParser.jj) by CSharpCC (https://github.com/deveel/csharpcc,
a port of JavaCC, now unmaintained). Due to limitations and/or bugs in the CSharpCC (eg. support
for namespace {}), the generated code must be rectified manually. A port to another parser
generator (eg. ANTLR) would certainly be required.
- selection is performed by the client, by browsing through the messages in the queue, via
MessageQueue.GetMessageEnumerator2(), and retrieving only the matching messages via MessageQueue.ReceiveByLookupId.
When the queue gets very long and the relevant messages are sparse, performance becomes an
issue.




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