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From sebb <seb...@gmail.com>
Subject Re: [DISCUSS] Deprecated code policy
Date Thu, 22 Nov 2012 18:40:45 GMT
On 22 November 2012 18:03, Gary Gregory <garydgregory@gmail.com> wrote:
> Hi all,
>
> <ot>
>   For US folks out there on the interwebs, Happy Thanksgving day to you
> all. In this context, I am thankful for this community of like and
> open-minded software gurus, tinkerers, and bit wranglers.
> </ot>
>
> I find it helpful to think about this in two parts: process and labeling
> (or what version to label code). This is my perfect version world:
>
> Process:
>
> I like to release one version N that includes @[D|d]eprecated code with a
> comment that states the EOL policy, e.g. "This class/method will be removed
> in version A.B" *AND* the doc MUST contain a pointer to what to do instead.
>
> The simplest process is to deprecate in version N and remove in the next
> (major) version N+1, e.g. 4.2 and 5.0.
>
> Labeling:
>
> Strictly, speaking I like API breakage in "major" releases only: 4.0, 5.0,
> 6.0 and so on. It's just simpler to think about even if it leads to
> "version inflation". When I pick up a new major version, I know what I am
> in for. In Commons-land, this is also an opportunity to offer co-location
> as a feature by renaming the package from o.a.project to o.a.project2,
> o.a.project3, and so on. This is what Commons Lang did for version 3. The
> POM AID should also be renamed at this time.
>
> I would only deprecate in a minor release (4.3), not a maintenance release
> (4.2.3). That's just because I don't expect surprises in maintenance
> releases, I expect a maint. release to be used in a drop and go fashion
> without deprecated warnings popping up. IOW, no new APIs in a maint release.
>
> HTTP Components
>
> How does this match up with this project? What's a good pragmatic approach?
>
> Well, now is a good time to talk about this since HttpClient will offer a
> new API.
>
> Today I can co-locate (I'm not sure what to call this feature) HttpClient 3
> and 4 because, this project is now a TLP and has a different package name.

HC4 is a completely different product from HC3, whereas what we are
discussing now is a gradual evolution.

> So my first question is: do we want to 'break' co-location for the new
> version or keep it? Do we want HC Next to live next to HC 4.2?
>
> The other way to ask this is: why would you not want to co-locate v4 and
> vNext.

Co-location - i.e. allowing both to play nicely in the same
classloader - is only necessary if there are systems that *need* both.

For example, JMeter uses both HC3 and HC4, but there's no reason for
it to use HC4 and HC4-new together.
JMeter will be amended as necessary to be able to use the updated API.

> All of this leads me to think that the new HC API should be in a version 5
> with a new package name.

Changing package name (and AID) does guarantee that the different
versions can co-exist.
However it means a lot more changes to source code.

With gradual introduction and removal of methods it's possible to phase updates.
However, if HC5 were to both introduce useful new methods and remove
deprecated ones this would make the update process slightly more
involved.

> From experience in a real world app server, I can testified that having
> Commons Lang 2 and 3 co-located is a genius feature which has avoid us
> countless headaches.

As I already wrote, Commons Lang is a very different proposition.
Headaches (jar hell) come from having multiple independent
dependencies on Lang in the same classloader and not being able to
update them all.
If there is only one dependency on Lang, that could be updated without problems.

If there are genuine use cases where multiple independent parts of a
system all depend on HC4, then yes, it might be worth striving for
strict binary compatibility.
But otherwise I think it's probably unnecessary overhead for HC4.

As to whether the next version should be 4.x or 5.0, I don't particularly mind.
A major version bump may make sense at this point.

> Gobble, Gobble,
> Gary
>
>
> On Thu, Nov 22, 2012 at 9:27 AM, sebb <sebbaz@gmail.com> wrote:
>
>> On 22 November 2012 13:46, Oleg Kalnichevski <olegk@apache.org> wrote:
>> > Folks
>> >
>> > There are lots of changes planned for the 4.3 series that will require
>> > many of the old implementation classes to be deprecated in favor of
>> > newer ones with a different API. While the amount of deprecated code
>> > will be moderate in HttpCore there will be LOTS of it in HttpClient. We
>> > should start thinking how we want to go about deprecated code in the 4.x
>> > code line.
>> >
>> > (1) We could keep deprecated functionality indefinitely to maximize
>> > compatibility. In this case we should start thinking about 5.0 and API
>> > incompatible changes soonish as we have already accumulated quite a lot
>> > of deprecated legacy code.
>> >
>> > (2) Alternatively, we could be selectively removing deprecated code
>> > after a certain number of feature releases (two feature releases) and a
>> > certain grace period (approximately two years) and keep 5.0 for some
>> > really major changes such as HTTP/2.0 or HTTP/1.1bis. By the way, this
>> > is what we have done about stuff deprecated in 4.0 GA.
>> >
>> > I am leaning more towards option 2 and therefore would like to proceed
>> > with removal of code deprecated in the 4.1 release from the 4.3 branch
>> > (both HttpCore and HttpClient).
>> >
>> > What are your thoughts? What would be your preference?
>>
>> Option 2 breaks binary compatibility, so is not suitable for all
>> libraries (e.g. it would not be suitable for Commons components, which
>> are likely to be referenced multiple times in the same classpath).
>>
>> However, in the case of HC, it seems very unlikely that a single
>> classpath will contain multiple independent dependencies on HC.
>>
>> So Option 2 seems the best way forward in this case.
>>
>> > Oleg
>> >
>> >
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>> >
>>
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>>
>
>
> --
> E-Mail: garydgregory@gmail.com | ggregory@apache.org
> JUnit in Action, 2nd Ed: <http://goog_1249600977>http://bit.ly/ECvg0
> Spring Batch in Action: <http://s.apache.org/HOq>http://bit.ly/bqpbCK
> Blog: http://garygregory.wordpress.com
> Home: http://garygregory.com/
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