Policy Framework in STP
This doc is aimed to define a framework to enforce SOA policy during developing and deploying service component. It includes
*Policy Model *Policy Registry *Policy Creation *Policy Validation *Policy Processor
Policy Data model
The policy model used here is different from policy defined in ws_policy or sca policy framework. It will focus more on the policy metaphor used during service creation and deployment.
David Bosschaert: How is it different? Is it only different in what it is used for? Regardless I think we should stick to the WS-Policy format for expressing policies.
Name, the name of the policy
Description, policy description
Category, such as transport, binding, security, and etc...
Version, policy version. We should support versioning in the policy framework
Metadata, the represented underline policy. It maybe a policy file or policy ID in the registry. For the policy file, it maybe a WS-Policy file or user proprietary xml file.
(Add Policy Model to STP Intermedia Metadmodel?)
David Bosschaert: We would also need a policy namespace; from my experience the namespace is the most convenient way of identifying policies. Additionally we might also consider describing dependencies and having a way of providing documentation.
David Bosschaert: One of the things that I'm really missing in this proposal is the difference between a Policy Template (or Policy Schema) and a Policy Instance. Policies instances are generally pieces of XML that are embedded in a WS-Policy document. These pieces of XML can (and should) be defined by an XML-Schema which one could call the Policy Schema. The Schema can contain basic XML-Schema supported validation constraints, but can also be used to hold other metadata, e.g. XML-Schema has a built-in annotation <xs:documentation> that can be used for documentation text. You add additional annotations if you wish to extends the XML-Schema with further metadata. I think that the above attributes should be obtainable from the Policy Schema. A Policy Instance is embedded in a WS-Policy document and takes the form of any XML tag (with sub tags and attributes) as long as it refers to the schema for its namespace.
The Policy Registry will be used to hold all policies to share cross projects. It will provide following functions:
*addPolicy *removePolicy *updatePolicy *listCategories *listPolicies *getPolicy
Due to the resource nature of the registry, we will implement it as a REST full service. We are looking for a generic tool to expose database table to REST service. If we can't find one, we may develop such a tool in STP.
In the first version, it will be implemented as XML file for simplicity. Later on, we will move to use embedded database (like Apache Derby) for better performance.
Policy Set Extension Point
Extension point to allow users to add pre-defined policy set to the registry. We will load those pre-defined policy sets during startup, and add them to the policy database.
It means to create policy with policy editor and associate policies to service component
There are two policy Editors in STP:
XEF Policy Editor: It is a generic schema based policy editor.
WTP based Policy Editor: provides a look & feel that is based on the WTP WSDL editor, supports WS-Policy documents with compositors (wsp:ExactlyOne, wsp:All)
The goal is to merge these two contributions into one editor that provides
- flexible editing of any WS-Policy document
- the ability to select between the views (schema based, wtp based, text)
- extension points to register new policy assertions schemas and optionally specialized GUI parts
Policy Association / Policy View
Policy View will list all of the policies associated with a service component. It allows users to add/remove policy. The add action will bring up the policy editor.
Here is the screenshot:
When a user add/move policy from service component, the policy validator will be called.
Policy Association during Deployment
Maybe the deployment profile editor needs to be extended to support applying policies at deployment stage.
The policy validation framework is used to define a validation mechanism when applying policies to a service component. Similar to policy editor. We will provide a policy validation rule editor for users to dynamicly add/remove validation rules as well.
The validation rules will cover the following categories:
Define dependency relationship between policies. For example:
<validation> <rule> <dependency policy_id = "policy A"> <on policy_id="policy B", version="2.0"/> <on policy_id="policy C"/> </dependency> </rule> </validation>
Define conflict relationship between policies For example:
<validation> <rule> <conflict policy_id = "policy A"> <with policy_id="policy D", version="2.0" /> <with policy_id="policy E" /> </conflict> </rule> </validation>
Policy Subject Constraints
Define the subject set which the policy may apply For example:"
<validation> <rule> <subjects policy_id = "policy A"> <subject>endpoint</subject> <subject>message</subject> </subjects> </rule> <rule> <subjects policy_id = "policy B"> <subject>message</subject> </subjects> </rule> </validation>
Policy Validation Engine Implementation
Need to write an engine to support the above validation rules. When users add/remove a policy, we will call the engine to do the validating, then give error message if applicable.
Need to looking into the emf.validation to see if we can use use it here. User defines the validation rules from GUI. How to translate those rules to emf validator class on the fly is a problem in that case.
rule based xml validator in stp
Alternative, we may think about extend the current rule based xml validator to support policy validation here.
Policy Artifact Processor
Policies will be translated into different runtime artifacts at various stages.
Policy to Artifact Mapping
Policies maybe be mapped to:
configuration file @Policy annotation WS-Policyattachment
When is the policies processed? I don't have the clear picture about the timing yet. I think we need to clearly divide the service creation and deployment into several stages. Then allow user to add customized processor at any stage by extension point.
Since the policy to runtime artifacts mapping is runtime specific. we will a provide processor extension point to allow users to hook the process function.
*Policy Developer -- write policies and policy validation rules. write policy processor. *Service Developer -- write policy, config and apply existing policy to service component. *Deployment Assembler -- apply policies to services during deployment *Operator -- dynamicly config/modify policies at runtime.
Relations with SCA Policy Framework?
The SCA policy association framework allows policies and policy subjects specified using WS-Policy and WS-PolicyAttachment, as well as with other policy languages, to be associated with SCA components.