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From Min Chen <min.c...@citrix.com>
Subject Re: [REVIEW/PROPOSAL/DISCUSS] API refactoring story: goal and notes
Date Thu, 20 Dec 2012 06:30:20 GMT
We will replace all IdentityProxy fields from all response classes with
simple String to represent UUID directly. If you look through API code,
most times when we generate response from queried resources, we already
query foreign key object once to fill in those related fields, like
accountName, domainName, etc. By replacing IdentityProxy fields, we can
directly save those already queried uuid in response instead of currently
querying them again during response serialization phase. For those more
costly list APIs, for example, listVms, we will create DB views to join
those uuids in the view to get them through one db view query.

Thanks
-min 

On 12/19/12 10:20 PM, "Anthony Xu" <Xuefei.Xu@citrix.com> wrote:

>Thanks for explanation,
>
>How does CS handle ID->UUID translation in response object?
>
>Anthony
>
>> -----Original Message-----
>> From: Min Chen [mailto:min.chen@citrix.com]
>> Sent: Wednesday, December 19, 2012 10:13 PM
>> To: cloudstack-dev@incubator.apache.org
>> Subject: Re: [REVIEW/PROPOSAL/DISCUSS] API refactoring story: goal and
>> notes
>> 
>> Here Fang is talking about UUID translation to DB_ID in constructing
>> our
>> Command class (ApiDispatcher.setupParameters), not in generating
>> response
>> object, so it will not impact list api performance.
>> 
>> Thanks
>> -min
>> 
>> On 12/19/12 10:07 PM, "Anthony Xu" <Xuefei.Xu@citrix.com> wrote:
>> 
>> >>2.	The API layer provides a translation from the UUID to the
>> internal
>> >>DB_ID to the DB entity, but this translation is done internally.
>> Outside
>> >>users will never see DB_ID. Before the response is sending back by CS,
>> >>API layer replaces the internal DB_ID with the UUID.
>> >
>> >I thought ID->UUID translation in API layer is a workaround, since it
>> >might cause list API performance issue.
>> >Any plan to fix it completely in backend?
>> >
>> >
>> >Anthony
>> >
>> >> -----Original Message-----
>> >> From: Fang Wang [mailto:fang.wang@citrix.com]
>> >> Sent: Wednesday, December 19, 2012 10:02 PM
>> >> To: cloudstack-dev@incubator.apache.org
>> >> Subject: RE: [REVIEW/PROPOSAL/DISCUSS] API refactoring story: goal
>> and
>> >> notes
>> >>
>> >> Prachi did an excellent FS document for this, and I added the high
>> >> level goals section
>> >> To her FS link at wiki:
>> >>
>> >>
>> https://cwiki.apache.org/confluence/display/CLOUDSTACK/CloudStack+API+r
>> >> efactoring
>> >>
>> >> Lots of implementation details are covered in the FS. We'll update
>> it
>> >> along the way.
>> >> Thanks,
>> >> -Fang
>> >>
>> >> -----Original Message-----
>> >> From: Fang Wang [mailto:fang.wang@citrix.com]
>> >> Sent: Wednesday, December 19, 2012 9:46 PM
>> >> To: cloudstack-dev@incubator.apache.org
>> >> Subject: [REVIEW/PROPOSAL] API refactoring story: goal and notes
>> >>
>> >> Hi all,
>> >> After answering questions about why/what we are doing to API
>> >> refactoring, I'll add this to the FS document.
>> >> Probably lots of people are not clear what is our motivation and
>> what
>> >> we want to achieve here.
>> >> (Will add this to the wiki page. )
>> >>
>> >> The goal of the API refactoring
>> >> To make the system more modular and dynamic, API refactoring is part
>> of
>> >> the 4.1 new architecture efforts.
>> >> Another goal is to allow developers and partners to quickly add
>> plugins
>> >> and new service modules and access control, making cloudstack more
>> >> adaptive.
>> >> I am new on this as well In the beginning, I do not know too much
>> about
>> >> it. Now after working on API refactoring, I got a better
>> understanding
>> >> of the existing problems and our solutions. The solution is not the
>> >> final perfect solution, for sure, feedback and suggestion is always
>> >> welcome to make it a much better and adaptive product.
>> >>
>> >> Current problem:
>> >> 1.	Security and access check is lying around in different layers.
>> >> For example, in apiSevlet we check the web access username/password
>> >> credentials, apiServer checks the command existence, and several
>> other
>> >> checks, then the DB access check mainly is done at the service layer.
>> >> So it is hard for developers and system admin to follow all the
>> access
>> >> and validations, to make sure all the checks are done correctly. To
>> do
>> >> it, developers need to be familiar with the various parts of the CS
>> >> code.
>> >>
>> >> 2.	Static: Majority of the DB access check and security validation
>> >> is tightly coupled with the lower layer service class. This not only
>> >> made the code hard to follow, also inherently made the policy static.
>> >> This makes it impossible for system admin to apply a different
>> security
>> >> policy adaptively. If one wants to adopt a different policy, not
>> only
>> >> he needs to understand code scattered around, he also needs to
>> rebuild
>> >> the CS after any changes.  Any security role modification is not
>> >> dynamic.
>> >>
>> >> 3.	Performance implication: Access check done at the lower service
>> >> layer makes the error code path long.
>> >>
>> >> 4.	Docs generated, CLI and APIs are loosely coupled.
>> >>
>> >> 5.	Over the wire(OTW) entity is not well defined. For example, to
>> >> listVMsCmd, it involves multiple DB access, with the large amount of
>> >> data showing NICs, Vols, Secondary storage etc, the command can take
>> >> quite a while.
>> >>
>> >> 6.	Admin and user have basically the same end-point access.
>> >>
>> >>        The goal of the API refactoring is aiming to tackle these
>> >> problems:
>> >>
>> >> 1.	We would pull security checks, DB access checks, any related
>> >> checks up from service layer/orchestration engine to the API layer
>> as
>> >> much as possible. This makes the necessary checking done more
>> >> centralized and easy to follow. Conceptually the cloud orchestration
>> >> engine layer handles the orchestration, the security check and the
>> >> access check should have done before reaching this layer. This has
>> >> performance benefits, since checks are done earlier instead of
>> reaching
>> >> deep in the code path; this also has the benefits of a clear
>> >> architecture. The API layer does the necessary access check and role
>> >> based authentication, makes it easier and dynamic for future policy
>> >> change. New policy can be added easily and dynamically as a plugin
>> to
>> >> the system.
>> >>
>> >> 2.	The ACL and security checks also are written as adapter plugins,
>> >> hence make them dynamic. Users and developers and easily adapt new
>> >> policy if needed. This made the code more modular and more adaptive.
>> >>
>> >> 3.	Help improves performance: Instead of finding access error layer
>> >> into the service layer, by doing 1, we would do possible checks
>> early
>> >> in the code path, which helps stop the wrong access earlier in the
>> code
>> >> path.
>> >>
>> >> 4.	API layer is more tightly coupled with Doc generation, and CLI.
>> >> Related commands are grouped together, and the new @Doc annotation
>> will
>> >> help show the related commands in document.
>> >>
>> >> 5.	We define new view objects as response objects, avoiding big DB
>> >> joins at run time.
>> >>
>> >> 6.	Separate the admin and user APIs. This is for developers to
>> >> understand the code, which should be accessible by users, which
>> should
>> >> only be handled by Admin.  Hence developers will have better grasp
>> of
>> >> the role and pay attention to the new code added. It also helps the
>> >> document generated.
>> >>
>> >>        Notes:
>> >> 1.	For end users, the new APIs after refactoring looks pretty much
>> >> the same. One big change is the ID, we will always use UUID in the
>> over
>> >> the wire APIs. The UUID can be created by Cloudstack, or can be
>> >> provided by users (we call it Xid - external ID). Every UUID should
>> be
>> >> unique in the cloudstack system.
>> >>
>> >> 2.	The API layer provides a translation from the UUID to the
>> >> internal DB_ID to the DB entity, but this translation is done
>> >> internally. Outside users will never see DB_ID. Before the response
>> is
>> >> sending back by CS,  API layer replaces the internal DB_ID with the
>> >> UUID.
>> >>
>> >> 3.	In original FS document, the annotation of entityType in
>> >> @Parameter points to a resource class, this is replaced by a
>> response
>> >> class. So entityType points to a response object, and the response
>> >> class has a one-to-one mapping from the response to the physical
>> entity
>> >> itself. This translation work is done by the API layer and the
>> >> entityManagerImpl.
>> >>
>> >> 4.	The packages for the new API commands are all moved from the
>> >> current com.cloud.api.commands to new location:
>> >> org.apache.cloudstack.api.commands.user.[group name]
>> >> org.apache.cloudstack.api.commands.admin.[group_name]
>> >>
>> >> The responses are also moved to new location at
>> >> org.apache.cloudstack.api.response
>> >>
>> >> More implementation details can refer to the FS document. We will
>> also
>> >> update the document along the way. The code is branch from master at
>> >> api_refactoring.  Since the change is not minimum, we would like the
>> >> community to know and give feedback.
>> >>
>> >> Thanks,
>> >> -Fang
>> >>
>> >>
>


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