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From "Bram de Kruijff (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (ACE-347) Redesign Management Agent
Date Wed, 28 Aug 2013 15:04:55 GMT

     [ https://issues.apache.org/jira/browse/ACE-347?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Bram de Kruijff resolved ACE-347.
---------------------------------

    Resolution: Fixed
      Assignee: Marcel Offermans  (was: Bram de Kruijff)

I have implemented the new agent in the org.apache.ace.agent project. It featuring resumable
downloads, retry-after support, persisted configuration, extension support for a number of
server, etc. 

Although I consider it alpha status I believe it mostly covers the concerns of this issue
and the related design page. As I will be unavailable for the next couple of weeks here is
an opportunity to thoroughly review and test it. 

Feel free to reopen if necessary or, even better, spawn new small improvement issues.
                
> Redesign Management Agent
> -------------------------
>
>                 Key: ACE-347
>                 URL: https://issues.apache.org/jira/browse/ACE-347
>             Project: ACE
>          Issue Type: Improvement
>            Reporter: Bram de Kruijff
>            Assignee: Marcel Offermans
>
> The Managent Agent was made "self-contained" in ACE-232 but there are still some concerns
with regard to complexity and functionality. This issue deals with restructuring the Managent
Agent code to make it easier to maintain, configure and extend. Also see ACE-324 / ACE-324.
> Management Agent code:   
> The MA implementation is setup very modular and it assembled mainly based on CM factories.
Maybe a little too much. The code is scattered over projects making it hard to maintain and
it is violating visibility rules to implementation classes which is nasty in bndtools.
> -> We should centralize the 'dedicated' MA code in the MA project allowing us to clean
up a lot of projects.
> Management Agent config:   
> The fact that we can theoretically reconfigure these services at runtime through CM does
not add much more then a runtime dependency on a CM impl. There is an obvisou catch-22 in
boostrapping and no mechanism to provision these configurations to a private CM and in fact
all configuration is done in code and it is very complex. 
> -> we should centralize configuration in a well documented format with a simple default
case and possible extension.
> Management Agent extension:   
> Bringing in extensions or customization on the bundle classpath is very hard on only
partially possible. There is a mechanism to disabled activators and one to add custom ones.
Theoretically one could also provide services from "user space", but there is no way do do
so in a simple way as there are no visible APIs and the CM catch-22.
> -> We should simplify extension on bundle classpath through a simple factory SPI.
Bringing these on the classpath can be done through wrapping (as launcher does) or maybe also
fragment bundles.
> -> User space extensions could have a real use case in management/monitoring. However,
this means we need to expose some API. Question is whether we want to expose prg.apache.ace.*
(or some subset) so that consumers can talk to for exmaple Log directly or that we should
facade this behind a single ManagementAgent API to keep it more contained.
> Multiple agents:   
> There is code to configure and handle multiple agents. Not sure if it really works as
it is a very exotic and possibly undesirable use-case. There are many conditionals for this
through the CM code.
> -> At least make it simpler and discuss wither we actually want/need this at all.
> Resource Processors:
> RPs need to resolve, typically requiring framework, deploymentadmin (spi) and eventadmin,
but maybe more. In the current situation the MA exports these package with an additional required
attribute (managementagent=true). As a result standard 3rd party RPs will not resolve. Therefore
the MA should be as self-contained as possible but still export these packages without the
attribute and (re)import them with the appropriate range.
> ----------------------------------- 
> UPDATE 10/8
> Restarted this effort @see https://cwiki.apache.org/confluence/display/ACE/Analysis+and+Design+for+new+ManagementAgent

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