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    This article was original hosted on the Overlord website, but has been relocated here following the web site restructuring.


    All good SOA platforms need a good SOA governance solution. Governance covers a number of factors and interacts at different levels of the SOA architecture. For example, there are tooling requirements (displaying the important information, customizing the view on the data, etc.) and infrastructure support (for enforcing SLAs, checking when they are [about to be] violated, etc.) The best governance implementations will perform well across these levels.


    So far we have been concentrating on the low-level infrastructure support for governance, both with JON and more native support within the ESB and other projects. Importantly from the start of our SOA Infrastructure development we've made the registry (UDDI in our case) a central component within the ESB, which helps drive some aspects of governance into the minds of users and developers. Plus, the Drools team have been making waves with their BRMS implementation, which is important in governance too and which we are going to be taking to new heights over the coming months along with ModeShape. However, what we haven't been able to do until now is discuss where we are going (both with in-house development as well as with partners).


    Aswell as tools from the individual projects within the SOA Platform, here is a brief synopsis of architectural requirements that will be addressed as part of the Overlord Project.


    Depending upon the role of the user or component some governance tools within Overlord to be Eclipse based, whereas others will be Web based. Plus there will be some tools that will have representations in both arenas because some of the capabilities will be need to be available across different roles in a format that is natural for that role. For instance, sometimes what a sys admin needs to do is also what a developer needs to do (e.g., inspect a service contract).


    As mentioned earlier, governance of SOA infrastructures is critically important. Managing a LAN-based distributed system can be hard enough: imagine expanding that so it covers different business domains where the developer or deployer do not control all of the underlying infrastructure and cannot work on the assumption that people are trustworthy (and possibly live on different sides of the planet!) With SOA governance there are run-time and design-time requirements: typically a runtime component executes to ensure things like Service Level Agreements (SLAs) are maintained, whereas a tooling-based governance component could be for run-time monitoring/management or design time service composition.


    With Overlord, you'll be able to graphically display (not a complete list):

    • MTTF/MTTRinformation on behalf of specific nodes and services on those nodes. Also for all nodes and services that are deployed.
    • throughput for services.
    • timetaken to process specific types of messages (e.g., how long to do transformations, how long to do transformations on behalf of user X).
    • number of requests sent to services during the lifetime of the service/node (in general, it is always important to distinguish between services and the nodes on which they execute).
    • number of faults (service/node) in a given duration.
    • information about where messages are being received.
    • information about where messages are being sent (responses as well as faults).
    • potential dependency tracking data. This can be used to determine sources of common failure. Can also be used when deciding whether or not (and where) to migrate services, for improved availability or performance.
    • what versions of services exist within a specific process (VM).
    • Includes sending probe messages that can test availability and performance on request. However, this functionality is also duplicated into the design-time tooling.


    All of this information may be obtained periodically from a central (though more realistically a federated) data store or direct from the services themselves. However, both sys admins and developers will need to be able to connect to services (and composites) and inspect their governance criteria at will, e.g., when was the last time they violated a contract, why and under what input messages/state: the dynamic factor is incredibly important. This information needs to be made available across individual services as well as the entire SOA-P deployment.


    Within the Overlord project we are working on a separate and dedicated governance console that is used to receive alarms/warnings when contracts/SLAs are violated or close to being violated. Obviously the console is only one such destination for these alerts: sys admin inboxes are just as important. However, that's where the infrastructure comes into play.


    Traditional management tooling (e.g., via JMX) including:

    • start/stop a service.
    • suspend/resume a service.
    • add/update restriction lists for services. This limits the list of receivers that a service considers valid and will process messages from. A similar list of destinations for responses will exist. This plays into the role/relationship concept because although a developer may not consider the issue of security (maybe can't, given that services could be deployed into environments that did not exist when the developer was building the service), the sys admin (or service container admin) will have to.
    • migrate services (and potentially dependent services).
    • inspect service contract.
    • update service definition.
    • attach and tune specific service parameters.


    Fortunately we'll get a lot of this from close integration with the JBoss Operations Network.


    Design time tooling from Overlord includes:

    • defining the service definition/contract, which includes specifying what message types it allows. This is tied into the service implementation in order that the SOI can verify incoming messages against this contract for validity. Part of the contract will also include security and role information which will define who can interact with the service (may befine grained based on time of day, specific message type, etc.) Policies are attached at this level on a per service or per operation basis (if not defined on an operation basis, the service level policyis taken if defined).
    • policy definition/construction,tracking and enforcement. Not just part of the development tool, but also an integral part of the underlying SOI. Policies need to be shared so that other developers can utilise them in their own service construction. Typically these will be stored in the repository.
    • service construction from other services, i.e., composite services. This has an input on SLA and on governance enforcement. In some cases a physical instance of the service may not exist either and the infrastructure becomes responsible for imposing the abstraction of a service by directing interactions accordingly.
    • inspecting the registry and repository during design time to locate and inspect desired services for composition within applications. Also ties into runtime management so that the user can inspect all running services.This would also tie into our graphical process flow tool, by allowing a drag-and-drop approach to application construction.
    • service development then into service deployment. The tool will allow the user to view a list of available nodes and processes. The availability,performance etc. of those nodes will also be displayed (more tooling and infrastructure support). Then you can drag a service implementation on to the node and deploy it, either dynamically or statically. This ties into the runtime management tool that allows the user to view deployed services on nodes.


    Service implementation tooling:

    • from the client perspective you go to the registry and select the right service based on requirements (functional as well as non-functional).The associated contract defines the message format, as mentioned earlier. The tool will either auto-generate an appropriate stub for the client code or provide a way of tying state variables (from the application code, or incoming messages etc.) in to the outbound invocations on the service. At the tooling level, we're really looking at defining client tasks that the developer writes and defines the output instance variables that are hooked into the service's input variables. As far as the client tool is concerned, we are simply tying together these variables. Capabilities such as security and transactions may be exposed to the client.
    • from the service developer perspective, we are defining services as compositions of tasks, actions, dispatchers etc. In the graphical designer we specify the input variables that are required for each operation type (defined as specific messages). This also plays into the contract definition effort mentioned earlier, since the message formats accepted by a service are implicitly defined by the requirements on input state variables.
    • WS-CDL tooling will also be tied into the run-time as well as design-time governance aspects of Overlord.
    • the need to be able to deploy services into a virtual environment to allow them to be tested without affecting a running system. A service has to be able to be deployed in a test mode. What this means is that at a minimum the service is not available to arbitrary users. Test services should also not be deployed into a running process/container that is being used by other (non-test) services and applications in case they cause it to fail and, worst case scenario, take the entire process with them.


    Very important to our work here was the donation by Thomas Erl of his Service Modeler.