[hibernate-dev] Introducing a new API in Hibernate Search to "sign" HTTP requests to Elasticsearch

[Yoann Rodiere]

> There's an important difference: one exposes Apache HTTP client in
> HSEARCH's SPI, whereas the other just requires usage of Apache HTTP
> client within one specific implementation. For users it doesn't change
> much, but the latter is cleaner from HSEARCH's perspective.

RestClient is not an interface, it's an implementation. There's no
interface. So yes, we would just be exposing Apache HTTP Client on top of
RestClient.

> I'm not quite following on that. If people are in control of the
> RestClient entirely, they can do whatever they want?

As mentioned above, exposing RestClient is even worse than just exposing
the Apache HTTP client.
So I was suggesting to use a proper abstraction, namely our own interface,
org.hibernate.search.elasticsearch.client.impl.ElasticsearchClient.

I suppose your remark concerned this paragraph:

> On top of that, this solution would not allow multiple third-party
> customizations to work well together (for instance AWS authentication
> provided by us or a third party + some performance tweaking by the
user)...
> which is something the SPI we're planning in the PR could allow.

If we did allow users to re-implement ElasticsearchClient, yes, one
implementor would be able to do whatever he wants... if he re-implements
it. He wouldn't be able to re-use other extensions.
Take for example the AWS authentication. You're suggestion that we provide
an alternative client allowing to connect to AWS. Fine, we do that, and
users can use it. But what if a users wants AWS authentication *and* say,
configure a proxy? Then he can't reuse our AWS client, since this client is
just an implementation of ElasticsearchClient, and we don't want to expose
anything related to Apache HTTP Client. So he must implement AWS
authentication. Just to configure a proxy.

The thing is, there are tons of things a user may want to do with Apache
HTTP Client, and we can't possibly provide access to each and every option
through an abstraction layer. So at *some* point, if we want to allow
configuration (and in the case of an HTTP client, I'm afraid we have to),
we'll have to expose internals. We just have to make sure this is done in a
controlled way (expose as little as possible).



Yoann Rodière
Hibernate NoORM Team
yoann at hibernate.org

On 2 June 2017 at 12:26, Gunnar Morling <gunnar at hibernate.org> wrote:

> 2017-06-02 11:58 GMT+02:00 Yoann Rodiere <yoann at hibernate.org>:
> >> Did you instead consider to just let users provide their custom
> >> instance of org.elasticsearch.client.RestClient? It's still leaking an
> >> implementation detail of Hibernate Search, but at least it's one
> >> indirection less.
> >
> >
> > The only way to add AWS authentication to the RestClient is to use Apache
> > HTTP Client classes, so this solution would still bind users to the
> > implementation details. We'd just shove it under the carpet :)
>
> There's an important difference: one exposes Apache HTTP client in
> HSEARCH's SPI, whereas the other just requires usage of Apache HTTP
> client within one specific implementation. For users it doesn't change
> much, but the latter is cleaner from HSEARCH's perspective.
> >
> > Also, I'd argue this would be an even bigger implementation leak: at
> least
> > with the current solution with can switch to an alternative Elasticsearch
> > client, as long as we still use Apache HTTP Client. If we expose
> RestClient,
> > we're stuck with it and whatever underlying technologies it uses.
> >
> > On the other hand, we could ask them to re-implement
> > org.hibernate.search.elasticsearch.client.impl.ElasticsearchClient,
> which is
> > our own façade over the Elasticsearch client. But I find it a bit much
> just
> > to tweak some settings or to add a new authentication scheme...
> > On top of that, this solution would not allow multiple third-party
> > customizations to work well together (for instance AWS authentication
> > provided by us or a third party + some performance tweaking by the
> user)...
> > which is something the SPI we're planning in the PR could allow.
>
> I'm not quite following on that. If people are in control of the
> RestClient entirely, they can do whatever they want?
>
> >
> > Yoann Rodière
> > Hibernate NoORM Team
> > yoann at hibernate.org
> >
> > On 2 June 2017 at 10:30, Sanne Grinovero <sanne at hibernate.org> wrote:
> >>
> >> On Fri, 2 Jun 2017, 08:56 Gunnar Morling, <gunnar at hibernate.org> wrote:
> >>
> >> > Hi,
> >> >
> >> > I find the exposure of an implementation detail (usage of Apache HTTP
> >> > client) of the Elasticsearch client a bit problematic. If they change
> >> > this to another HTTP client, our SPI would break.
> >> >
> >>
> >> Yes the very point of exposing that detail is the reason for this
> thread.
> >>
> >> Still, our SPI being guaranteed only for a minor, that gives a lot of
> >> flexibility?
> >>
> >> The Elasticsearch client exposing this itself, I don't expect them to
> >> switch implementation in a micro release to make some bugfix. If they
> >> change it in a major or even minor version, we're ok to not support that
> >> version until our next minor.
> >>
> >>
> >>
> >> > Did you instead consider to just let users provide their custom
> >> > instance of org.elasticsearch.client.RestClient? It's still leaking
> an
> >> > implementation detail of Hibernate Search, but at least it's one
> >> > indirection less.
> >> >
> >> > People wishing to have a custom RestClient would have to implement a
> >> > few more bits themselves (the logic from
> >> > DefaultElasticsearchClientFactory#customizeHttpClientConfig()), but
> >> > I'd find that acceptable for the sake of a less detail-exposing SPI,
> >> > plus it grants more flexibility in terms of configuring the
> >> > RestClient.
> >> >
> >>
> >>
> >> N.B. The client factory already is a Service so any advanced user
> already
> >> can override it.
> >>
> >> We want to make it easier for cloud users. Focusing on AWS now as we've
> >> had
> >> user requests for this - not least our own CI - but I'd expect other
> >> clouds
> >> to have similar features (today or tomorrow). I just don't expect other
> >> use
> >> cases to need this so we might provide them all eventually, but at this
> >> point my goal is to leave an appealing SPI for contributors to join on
> >> that.
> >>
> >> With that I mean:
> >> 1# this might evolve but we need something simple to use for people to
> not
> >> get stuck.
> >> 2# I expect integrator implementors to contribute them back
> >> 3# People won't have this low level dependency in their projects for
> long
> >>
> >> Having them re-implement the client wouldn't encourage this ;)
> >>
> >> Thanks!
> >> Sanne
> >>
> >>
> >> > --Gunnar
> >> >
> >> >
> >> > 2017-06-01 19:11 GMT+02:00 Sanne Grinovero <sanne at hibernate.org>:
> >> > > Yoann has been working on allowing Hibernate Search users to use
> >> > > Elasticsearch on AWS.
> >> > >
> >> > > Specifically on AWS the Elasticsearch security can be configured to
> >> > > use application identities, which implies the requests need to be
> >> > > signed.
> >> > >
> >> > > A good background read can be found here [1].
> >> > >
> >> > > We planned to allow people to use this but were not planning to
> >> > > include AWS specific libraries as dependencies - but since Yoann
> >> > > implemented an actual AWS signer in the tests I suppose it would be
> >> > > selfish to not ship it..
> >> > >
> >> > > Please see the API proposal on github (with the PR):
> >> > >  - https://github.com/hibernate/hibernate-search/pull/1426
> >> > >
> >> > > Thanks,
> >> > > Sanne
> >> > >
> >> > > [1] -
> >> >
> >> > https://aws.amazon.com/blogs/security/how-to-control-
> access-to-your-amazon-elasticsearch-service-domain/
> >> > > _______________________________________________
> >> > > hibernate-dev mailing list
> >> > > hibernate-dev at lists.jboss.org
> >> > > https://lists.jboss.org/mailman/listinfo/hibernate-dev
> >> >
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