[hibernate-dev] [Hibernate Search] Donating some of our source code to Infinispan

[Sanne Grinovero]

On 26 January 2015 at 15:05, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
> One angle that is a bit unclear to me is how easy is this consumable and discoverable by our users.

Discovery would be the same as today, same configuration property.
We have your "resolution strategy" which translates from short name to
fully qualified name, which is already "pluggable" in the case of the
IndexManager lookup. So we have plenty of options A) look for the new
FQCN B) plug a custom resolver strategy for the DirectoryProvider
names C)use the custom IndexManager: we had already decided at our f2f
meeting that it would be far easier for people to only have to choose
the IndexManager implementation, which would be in charge of setting
up the right backend/directory couples as a "profile".

WildFly users don't even need to know about changes in the module
names / jar names / maven coordinates as the instructions would still
be: download both modules, drop them in your AS -> works.

In short, we can keep user changes to minimal.

> Some in this thread mentioned creating a separate repository. I see this as a massive ease of use problem if the user is exposed to finding the right version of each of these three libs. Likewise for documentation, project identity, etc.

+1 not my preferred choice either. I think we'll stick to my plan, at
least until I'm proven this proposal is utterly broken.

> I think the merge of this piece of code into Infinispan does not create too much of a problem in that regard. The main issue is that as an Hibernate Search user, I don’t know which Infinispan to target. And an Infinispan user does not really care for the most part about an explicit HSearch usage outside Infinispan query.

We'll have to document that. Indeed quite tricky, as there might be
cases in which there is no compatible version of Infinispan whatsoever
(for example each time we migrate to a new Lucene there would be a
gap).. but my hope is that would be some Alpha/Beta, and by the time
of a Final release we'd have a viable suggestion, with more options
while the branch matures in maintenance mode.

> BTW will the documentation on HSearch integration with Infinispan Lucene Directory remain in HSearch’s doc or be copied in Infinispan’s?

I'd prefer to have a single consistent document for our users to read:
we'd have the high level description from the point of view of an
Hibernate user, and exposing to the subset of tuning options which
make sense to him.
Infinispan should have a different copy, especially as it's becoming
clear that tuning and configuration for this specific component is
quite different in the two different use cases. Ultimately both
"engines" should be able to guess and auto-configure several options
which are manual today, and these guessing and custom backends are
different.
The low level details of the Directory tuning should probably live in
Infinispan only, in close coupling to the code changes, to make sure
there is a document set kept in synch with the specific version. From
experience we know the new configuration options needed by Infinispan
are rarely in the "need to know" for Hibernate users.

Sanne

>
> Emmanuel
>
>> On 25 Jan 2015, at 22:19, Sanne Grinovero <sanne at hibernate.org> wrote:
>>
>> All,
>> we've discussed several times the issues we have because of the
>> circular dependency between Hibernate Search and Infinispan.
>> Normally the pain point we aim to address with such discussions is the
>> need to carefully coordinate between releases [of Search and
>> Infinispan] in our quest for a final stable release, and brings some
>> release pressure.
>>
>> More recently it has also become a compatibility problem, as the two
>> projects target different platforms/environments, and have different
>> life-cycle expectations - creating more maintenance work such as lots
>> of back-porting of patches.. distracting from our goals.
>>
>> We already discussed some solutions, but none too convincing. I have a
>> new fresh proposal which I feel is more interesting:
>>
>> # New plan
>>
>> 1) the module "/infinispan" from the Hibernate Search source tree is
>> moved to the Infinispan project into some "hibernate-search-directory"
>> Maven module.
>>
>> 2) Hibernate Search drops any dependency to Infinispan
>>
>> Reminder: this "/infinispan" module we have contains just a couple of
>> classes, and represents the "DirectoryProvider" implementation which
>> integrates with the Hibernate Search autodiscovery and creates a
>> Directory instance (whose implementation always lived in Infinispan).
>> Most of the code is about applying configuration properties,
>> integration tests.
>>
>> It's a very simple plan, but has some valuable consequences:
>> - Search can move on without ever needing to wait for Infinispan -
>> and vice versa.
>> - There is no longer a circular dependency
>> - Search would be in control of its Lucene dependency, and can
>> upgrade as needed. We could experiment with different Lucene versions
>> without necessarily wait for Infinispan to solve compatiblity issues
>> first - and often more complex as that means then for Infinispan to be
>> able to guarantee a compatibility with a *range* of Lucene versions,
>> to include both the target Lucene and the version currently consumed
>> via Infinispan Query / Hibernate Search Engine.
>> - Infinispan can *opt* to stick with an older version of Search - or
>> update - provided it can satisfy both a) integration with possible
>> changes to the Search SPI b) an update for possible new requirements
>> of the new Lucene version (the Lucene Directory might need
>> compatibility fixes)
>> - The dependency structure would better match the one as provided by
>> our Enterprise Products. For example, it's the JDG distribution - not
>> Hibernate Search - to provide these integration bits, so it makes more
>> sense to build the Directory against the specific version of
>> Infinispan than against the specific version of Search.
>> - It will be easier to have new Infinispan code take advantage of
>> features exposed on the Infinispan Lucene Directory - if all changed
>> parts are in the same [Infinispan] repository. This is actually being
>> a problem right now, as it's holding back a POC meant to deliver great
>> improvements with the Directory implementation.
>>
>> And not least we'll have faster builds ;-)
>>
>> # Drawbacks
>>
>> First one is we'll probably have our users need to change some details
>> of how they build.
>> Infinispan might need to fix some SPI related code before being able
>> to upgrade, but historically our SPI has been extremely stable.
>> The real problem is that when such a thing happens, after we've
>> released a version of Search there might be some time before a
>> compatible version of Infinispan is made available as well.
>>
>> In practice this means the gap of time in which we have to catch up on
>> API changes is "exposed" to end users wanting to use our latest and
>> possibly blocked - but while they would then see the tip of the
>> iceberg of our integration, I believe it would still take the same
>> amount of waiting time in terms of calendar dates in which the working
>> duo is available to them - as with the current model in such a
>> situation we need to wait for the same Infinispan release to happen
>> before we can release ours.
>> So: same time, but we'd have a leaner process, and possibly quicker
>> releases for all users not interested in that - or just benefits in
>> all those scenarios in which we don't break APIs which is very common.
>> I've not identified other problems, so my opinion is that these are
>> well worth the benefits.
>>
>> # Consequences for our users
>>
>> Not much. Even today we expect our users to depend on several jar
>> files provided by the Infinispan team; this would be just one more.
>> Opens some questions though:
>>
>> A) Should the Maven group id be changed? I'd expect it to be
>> transferred to "org.infinispan" group at least, and probably need a
>> better artifact id too.
>>
>> B) License. Our code is LGPL, most of Infinispan is ASL - but not all
>> of it. So I expect it would be possible to keep the existing license
>> at least for now, and defer eventual license changes as a separate
>> step (if people feel need for any change at all).
>>
>> C) Documentation. Besides the needed updates in Maven coordinates /
>> download sources, I don't expect much of a difference: we'd still
>> explain how to set this integration up.
>>
>> D) Distribution. Today we distribute this module, and its
>> dependencies, in our release bundles. Which implies we distribute a
>> copy of various Infinispan jars.
>> I think we should drop these from our distribution - even though it
>> might seem counter-intuitive:
>> while it might seem convenient to have these included, the whole point
>> of the change would be that there would be more flexibility in which
>> versions of Infinispan would work with Search. And actually the
>> integration tests and this specific knowledge would be responsibility
>> of Infinispan.
>>
>> Am I failing to see a more critical issue?
>> How would you all feel about our code being transferred to the
>> different project?
>>
>> Sanne
>> _______________________________________________
>> hibernate-dev mailing list
>> hibernate-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>