[wtp-dev] Server API change proposal

["Thomas Yip" <tyip@xxxxxxx>]

Introduction

This proposal briefs the limitation we see with current server publish API, and it suggests a solution. We had a short discussion during a conference call on Mar 13^th, 2006. (mainly around the ServerBehaviourDelegate). The problem is also related to https://bugs.eclipse.org/bugs/show_bug.cgi?id=123676

 

Current API

We learned the original design was driven by a need of a very simply publish mechanism.

1. an adopter should able to implement a simply delegate and do the publish work.
2. publish tasks was intent to be simple task.
3. most methods can be overridden.

 

BEA use-cases

We found the current API is not ideal for BEA needs.

 

We delay much of publish process until user do an explicit publish action (menu item publish, or Run on Server).

 

1. We generates *.java file based on annotation of Java file in publish time. We trigger project rebuild during process.
2. We insert information into application descriptors (web.xml, application.xml) based on files on the project.
3. Generated artifacts can cause changes to the EAR or other modules in the same application.
4. Publish application by application.
5. Publish failure should be isolated between modules.

 

For us, the publish process is better described as a 3 steps process: Assembly (artifact generation), Packaging (we package virtually), and Distribution (calls JSR-88 to distribute the application to the server).

Limitation

The current SPI was driven by the need of simple publishing. The publish process iterates module by a flattend module list (not application by application.)

 

Because that most methods can be overridden, we can achieve our goal reasonably well. However, it incurs maintenance risk, because are not really implementing the delegate’s SPI. For example,

1. if a fix or an enhancement is made to PublishOperation, our server adapter lag behind, and enhancement will not be supported.
2. We short circuit a few methods, such as publishModules() (which is a violate the interface). If any of the methods is called by new code that we haven’t overridden, it causes unexpected behaviour.

 

Because of the different design goal, we don’t implement the full spec of ServerBehaviourDelegate. While such changes might not be likely, an adopter should not be required to implement their delegate in a way to violate the SPI contract.

Solution

Required changes

We can eliminate the problem by the following changes:

 

1. Introduce another delegate. Let’s call it BaseServerBehaviourDelegate for now. The current ServerBehaviourDelegate should make extended of BaseServerBehaviourDelegate. Most generic methods can be push up. (such as state settings, module controls, resource delta maintaince. But, it leaves out
1. code related to published module list, and the kind. PublishOperation, and
2. all the publish methods. Introduce an adapter interface to indicate PublishOperation is supported.

 

The changes will maintain compatibility for all current adopter, and the original design goal. It enables adopter with different needs to have full control of the publish process.

 

2.  
1. Either, makes publish operation optional. Push down PublsihOperation related code to the original ServerBehaviour Delegate.
2. Or, factors out PublishOperation into utility class or method.
3. Or, made PublishOperation not depends on the flatten module path (IModule[] representing the sub module and its parents).
3. Introducing another extension point for UI to replace the hard-coded publishTask page fragment. Move UI for publishOperation as an extension.

 

A brief study of the code indicated that we should able to implement it in a way that it doesn’t affect existing adopter.

 

Optional changes

A few optional changes can be introduced to ease the work of an adopter.

 

1. Publishing application-by-application is common to many servers. We might want to introduce another BehaviourDelegate.
2. Generic server is already use application-by-application approach. We should look into merging the requirements.
3. Going further, we can also introduce the 3 steps publish process for adopter with complicated publish use-case.

 

 

 

--------------------

Thomas Yip

Senior Software Engineer

BEA Systems

Email: tyip@xxxxxxx    YIM: thomasleaf    Phone: (206) 926-2906   Blog: http://theBigGrid.com/

 

"The complexity you remove can never fail." Burt Rutan.

 

 

 

 

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