Introduction
This document is meant to give a high level overview of CMS (C++ Message Service). CMS
is a JMS-like API for C++ applications. The idea being that someone who is familiar with JMS
can move seamlessly between languages. As those of us who have had the unfortunate luck
of being stuck back on a legacy C++ project know – it’s really hard to go back to C++.
Hopefully this will make it a little less painful.
Architecture Overview
The implementation of CMS is a 3-layer stack, as shown below.
The client interfaces with the CMS API directly. This API is defined by the interfaces in the
cms namespace. These map 1 to 1 (for the most part) to interfaces defined by the JMS spec.
ActiveMQ CMS is an implementation of the CMS interface. This layer is abstracted from the
specifics of the protocol being used to talk to the ActiveMQ broker. Instead it is a middle layer
between the transport layer and the client. It manages client connections, sessions,
subscribers, publishers, etc.
The Transport Protocol layer deals with the specifics of broker communications. It manages
connection state, message protocol conversions, and is responsible for notifying the CMS
layer when client messages arrive from the broker or when exceptions occur.
Source Code Overview
The CMS code is currently divided into 2 eclipse projects (eclipse 3.1.1 with CDT 3.0.1): cms
and activemqcms. These projects are configured as managed make projects, so I’m not sure
if they will be able to be built outside of eclipse. Also, as it stands now, these projects require
pthreads, the linux socket API, and the sys/time.h header (nanosleep, etc). It should be fairly
easy to replace these dependencies with an all-in-one library (such as boost) in the future.
The source for both projects is stored under the src directory. Under the src folder, I have
maintained a directory structure matching the namespace hierarchy.
The cms project only contains the cms namespace. No library is generated from this project
because it only contains header files. The file/class names in this namespace closely match
those of JMS.
CMS (API)
ActiveMQ CMS (connections, sessions, ... )
Transport Protocol (STOMP, OpenWire, etc)
