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From: Carsten Ziegeler <cziegeler@apache.org>
Subject: Re: [RT] Context-Aware Services - Multitenancy for SPI
 implementations
To: dev@sling.apache.org, Stefan Seifert <sseifert@pro-vision.de>
References: <0f1512a2205a44d79a594fc299d9c070@mailx01.intern.pro-vision.de>
Message-ID: <8ccb5e9c-6d19-10b2-69d9-1817ea192592@apache.org>
Date: Tue, 12 Sep 2017 10:41:02 -0700
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archived-at: Tue, 12 Sep 2017 17:41:07 -0000

Hi Stefan

this is definitely an interesting approach. I can see the potential, but
so far I haven't really seen use cases (which doesn't mean there are non).

If I understand correctly, you do the matching based on the path which
avoids the need of introducing an explicit concept of a tenant. On the
other it requires you to have a corresponding resource or request. I
assume for most of the use cases this works as they are request bound
anyway. And even for background tasks you should have at least some
resource. I guess this should be sufficient.

I'm a little bit worried about the reliability, for example if a bundle
providing a specifc SPI interface is currently not active, you get
(temporarily) a different result. This might be fine as well.

In general, I'm unsure :) this sounds useful, but of course complicates
things and the general execution.

Regards
Carsten

Stefan Seifert wrote
> consider the following use case:
> - an OSGi/Sling-based library provides a SPI interface
> - applications of multiple tenants are deployed on the same instance
> - each tenant uses a different content tree, e.g. /content/tenant1 and /content/tenant2
> - each tenant's application wants to register a different implementation of the SPI, to be applied on resource requests on the tenant's content subtree
> - this affects not only one SPI but multiple SPIs
> - we do not want to implement a detect-the-matching-SPI-implementation-for-a-given resource for each library again
> - we want to have a configuration of the mapping tenant's resource path -> SPI implementation in a central place and to be applied to all SPI implementation of a tenant's application
> 
> i've implemented a solution for this some months ago, it's currently part of a wcm.io library.
> documentation [1], source code [2]
> 
> questions:
> 1. do you have these use cases as well? (we had a lot of enterprise projects where we needed exactly this in the last years)
> 2. does it make sense to contribute it to sling?
> 3. do you have better ideas for configuring the mapping or the implementation?
> 
> stefan
> 
> [1] http://wcm.io/sling/commons/context-aware-services.html
> [2] https://github.com/wcm-io/wcm-io-sling/tree/develop/commons/src/main/java/io/wcm/sling/commons/caservice
> 
> 
> 


-- 
Carsten Ziegeler
Adobe Research Switzerland
cziegeler@apache.org