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

[Gunnar Morling]

2017-06-02 12:49 GMT+02:00 Yoann Rodiere <yoann at hibernate.org>:
>> 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.
>

Here's what I'd have done:

    package org.hibernate.search.elasticsearch.client.spi;

    public interface RestClientFactory  {
        RestClient buildRestClient(SomeContext ctx);
    }

There's no exposure of HTTP Client in this SPI. Yes, if people need to
customize the HTTP client to be used by the returned RestClient
instance, they'll naturally depend on that. But this SPI isn't tied to
such detail of how RestClient works - if ES folks decided to use
OkHttp instead, our SPI contract won't be affected (of course user's
implementations will need to change if they were customizing the HTTP
client before).

>> 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.

I don't think it's worse, it's better actually. It just exposes our
direct dependency in the SPI and not any of its details.

> 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.

Right, hence I wouldn't bother to do that in the first place. Just let
users customize how RestClient is instantiated. Let's them do all they
want. We can provide examples which show how to do the AWS signing
etc.

> 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/
>> >> > > _______________________________________________
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>> >> > > hibernate-dev at lists.jboss.org
>> >> > > https://lists.jboss.org/mailman/listinfo/hibernate-dev
>> >> >
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>> >
>
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