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From "Zheng, Kai" <kai.zh...@intel.com>
Subject RE: [backend] AbstractIdentityBackend interface
Date Wed, 01 Jul 2015 03:27:38 GMT
>> no, once we decouple this cache in AbstractIdentityBacken we don't need these doXXX()
anymore

You said NO, but I don't think you are clear about what I had tried to explain. Let me have
some illustration and hope it helps.

Interface IdentityBackend {
    List<String> getIdentities(int start, int limit);
}

Class abstract AbstractIdentityBackend implements IdentityBackend {

    public List<String> getIdentities(int start, int limit) throws KrbException {
      // check and validate parameters start and limit, adjust them if necessary
     // check any preconditions
    try {
        return doGetIdentities(adjustedStart, adjustedLimit);
    } catch (SomeException e) {
       // convert e and throw a KrbException
    }
   }
}

Here, I thought doGetIdentities() works nicely and I don't think we have to remove it. All
the subclasses extending AbstractIdentityBackend can share above block of codes and don’t
have to repeat the same parameter checking, exception handling and etc. 

The above pattern is a common OO pattern, and is widely used in Kerby project. If you plan
to get rid of this pattern, are you going to get rid of all of them? What's the pure benefit
for such change? 

If you don't like this pattern, I would suggest you start with the Mavibot backend from new,
instead of extending AbstractIdentityBackend that's already used by memory, json, zookeeper
and ldap backends.

Regards,
Kai

-----Original Message-----
From: Kiran Ayyagari [mailto:kayyagari@apache.org] 
Sent: Wednesday, July 01, 2015 10:58 AM
To: kerby@directory.apache.org
Subject: Re: [backend] AbstractIdentityBackend interface

On Tue, Jun 30, 2015 at 1:37 PM, Zheng, Kai <kai.zheng@intel.com> wrote:

> Thanks Kiran for the clarifying.
>
> >> no, this is a different one that stores all data in a single file 
> >> in
> binary format
> >> yes, LDAP backend needs a server, whereas mavibot backend stores
> locally on disk
> This sounds good. Which one would ApacheDS prefer to use? This one or 
> the LdapIdentityBackend?
>
when integrated with ApacheDS it initializes Kerby with LdapIdentityBackend

>
> >> ic, I see that these doXXX() are for subclasses, but we can 
> >> completely
> avoid these methods, see below
> I mentioned cache stuff just as a sample. Even if we get rid of the 
> cache facility as you suggested, I thought doXXX() methods may still 
> validate. I meant, for subclasses, they don't have to start with 
> interface

no, once we decouple this cache in AbstractIdentityBacken we don't need these doXXX() anymore

> methods directly every time, instead internal methods like doXXX(), 
> because doing the way would allow sharing template codes in the 
> abstract class.  For now, the shared codes are just cache related, 
> later we can enhance and add more, like parameter checking, exception 
> handling. Please note this pattern isn't rare, and is widely used 
> across the project. That's why I still have some concerns for the proposed change (removing
them).
>
there will not be any side effects with this change

>
> >> This AbstractIdentityBackend ia always utilizing a cache and this 
> >> is
> enforced on all backends that subclass this, instead what we should do 
> is to create a CacheableIdentityBackend which wraps an instance 
> IdentityBackend and maintains an internal cache, and calls are 
> delegated to the wrapped backend when a cache miss happens.
> >> This way implementations of IdentityBackend will be free from the 
> >> side
> effects of caching while testing and also become simple and cleaner.
> This sounds great!! I'm fine to change and support the cache in this 
> new way. I thought it's another issue to process.
>
> this is just part of the design, I will refactor them after finishing 
> the
Mavibot backend

> How do you think? Thanks.


> Regards,
> Kai
>
> -----Original Message-----
> From: Kiran Ayyagari [mailto:kayyagari@apache.org]
> Sent: Tuesday, June 30, 2015 11:49 AM
> To: kerby@directory.apache.org
> Subject: Re: [backend] AbstractIdentityBackend interface
>
> On Mon, Jun 29, 2015 at 9:10 PM, Zheng, Kai <kai.zheng@intel.com> wrote:
>
> > Thanks Kiran for the taking.
> >
> > >> I am implementing a Mavibot based backend*.
> > Would you clarify a bit about this? I'm wondering if it's the same 
> > thing, the on-going LdapIdentityBackend Yaning is working on?
> >
> no, this is a different one that stores all data in a single file in 
> binary format
>
> > Or you mean something that uses Mavibot directly instead of by the 
> > LDAP connection API?
> >
> yes, LDAP backend needs a server, whereas mavibot backend stores 
> locally on disk
>
> >
> > >> Is there any reason why the API methods start with doXXX()?
> > I would think AbstractIdentityBackend isn't the interface, and the
> > doXXX() methods are not the APIs.
> > Please see the APIs in the interface IdentityBackend/IdentityService.
> >
> ic, I see that these doXXX() are for subclasses, but we can completely 
> avoid these methods, see below
>
> > AbstractIdentityBackend is a common abstract class to implement the 
> > API interface, and provides some useful functionalities like cache.
> >
>
> This AbstractIdentityBackend ia always utilizing a cache and this is 
> enforced on all backends that subclass this, instead what we should do 
> is to create a CacheableIdentityBackend which wraps an instance 
> IdentityBackend and maintains an internal cache, and calls are 
> delegated to the wrapped backend when a cache miss happens.
>
> This way implementations of IdentityBackend will be free from the side 
> effects of caching while testing and also become simple and cleaner.
>
>
> I thought if you don't like it, you could start with totally new,
> > implementing IdentityBackend/IdentityService directly.
> >
> > I hope the above reasons make the intention behind this proposal 
> > clear
>
> > >> now is the time after today's commits in Mavibot trunk that 
> > >> address
> > these bugs.
> > Glad it's the time now. It will help a lot.
> >
> > Regards,
> > Kai
> >
> > -----Original Message-----
> > From: Kiran Ayyagari [mailto:kayyagari@apache.org]
> > Sent: Monday, June 29, 2015 5:43 PM
> > To: kerby@directory.apache.org
> > Subject: [backend] AbstractIdentityBackend interface
> >
> > I am implementing a Mavibot based backend*.
> >
> > Is there any reason why the API methods start with doXXX()?
> > This looks a bit odd and hard to read.
> >
> > I would like to strip the 'do' verb from these methods, please let 
> > me know if there are any objections.
> >
> > * this is on hold for a long time due to the free page management 
> > bugs, but now
> >    is the time after today's commits in Mavibot trunk that address 
> > these bugs.
> >
> > --
> > Kiran Ayyagari
> > http://keydap.com
> >
>
>
>
> --
> Kiran Ayyagari
> http://keydap.com
>



--
Kiran Ayyagari
http://keydap.com
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