Re: [PATCH v4 0/4] Basic binary cache implementation

[Alexander Smirnov <asmirnov@ilbers.de>]

On 10/04/2017 02:57 PM, Jan Kiszka wrote:
> On 2017-10-04 10:32, [ext] Claudius Heine wrote:
>> Hi,
>>
>> On 10/0    '2/2017 05:45 PM, Alexander Smirnov wrote:
>>> Hello everybody,
>>>
>>> this series introduces basic binary caching for Isar.
>>>
>>> There is a new layer: meta-isar-bin which is intended to be the binary
>>> cache. All the packages that are built in Isar are stored in this
>>> cache using reprepro.
>>>
>>> Having the separate layer makes possible to manage this cache separately
>>> from the Isar build tree. So once you have built your packages, you could
>>> re-use this cache for further builds.
>>
>> We still have to talk about your requirement for the cache to be
>> sharable and your resulting implementation of it as a meta layer.
>>
>> Since I still don't see the benefit of a sharable cache and think that
>> putting binary packages into some kind of strange meta layer is not the
>> right solution and could potentially create more problems that is solves
>> because its very much in conflict with the fundamental idea of a meta
>> layer.

The last statement is a bit strange for me. The idea of meta layers is 
to split software stack into logical layers that could be 
enabled/disabled on demand. Having binaries or recipes doesn't matter 
here, it's just the way how software is provided to build.

> 
> Indeed, state like this (disclaimer: i didn't look into all details), it
> sounds like a weird architecture to me as well. Thinking of an artifact
> cache, I would rather expect something like OE's sstate that one may
> preserve across builds, share between devs, or whatever. If it's there,
> the build system consults it, if not, it rebuilds. But sstate is not a
> layer, for some good reasons.
> 

Let me again summarize major points here. Isar is the build system 
designed to work with binary packages. That's the key feature of this 
product and main difference from OE-like systems. The Isar architecture 
assumes to be designed around binary packages, what provides absolutely 
different approach how binary images could be generated using bitbake.

According to the Claudius's vision, that everything should always be 
built from sources - Isar is not the best option here, Yocto and OE are 
much better, because they were initially designed for this work. 
Attempts to apply OE design and philosophy to Isar could have negative 
impact and limit possible ways to implement custom features, because OE 
wasn't designed for this features.
Also I wonder why we are able to use binary Debian packages, while the 
rest of software should be built from sources.

This series introduces support for binary apt repositories in Isar. This 
feature is response to the following cases:

1. Publish custom apt layer in web. When I need to install some custom 
software to my Debian system, I frequently see instructions like:
  - Add 'blablabla' to your /etc/apt/source.list
  - Run apt-get update
  - Run apt-get install

That's for example how Jenkins and GitLab are distributed:

   https://pkg.jenkins.io/debian/

The management of this public apt could require some manual effort, 
while Isar (in plans) could update it automatically, so you update 
source code for your product, run Isar and it provides complete apt that 
you could upload to your server.

2. Implement easy software update. On our host systems we usually do not 
flash whole image if we need to update some packages. The update is 
performed using 'apt-get install' (or by similar tool). But in this case 
  binary repo is needed, what could be again provided by Isar.

Please do not limit Isar by deep embedded application, host systems also 
could be managed by Isar.

3. In long term, help Debian community to manage Debian infrastructure, 
what includes publishing apt updates.

-- 
With best regards,
Alexander Smirnov

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