Re: [cross-project-issues-dev] Producing downloadable p2 repositories

[John Arthorne <John_Arthorne@xxxxxxxxxx>]

Hi Anthony,

We're unfortunately not in a position
to be able to tell people what they must do ;). We were hoping to provide
sufficiently convincing arguments that you would *want* to provide zips
of your repositories, since this makes it much easier for downstream components
and products to consume your project's binaries and metadata (and a happier
Eclipse Foundation due to reduced disk footprint and bandwidth use). And
making life easier for your consumers is typically in projects' best interests...

John

Anthony Hunter/Ottawa/IBM@IBMCA
Sent by: cross-project-issues-dev-bounces@xxxxxxxxxxx

02/10/2009 12:16 PM

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Subject	Re: [cross-project-issues-dev] Producing downloadable p2 repositories

Hi John,

Your email says "The p2 team is now recommending". It is not
clear to me what you are asking of projects for Galileo, if anything. 

Cheers...
Anthony
--
Anthony Hunter mailto:anthonyh@xxxxxxxxxx
Software Development Manager: Eclipse Open Source Components
IBM Rational Software: Aurora / GEF / GMF / Modeling Tools 
Phone: 613-270-4613

John
Arthorne---02/10/2009 09:49:48 AM---If you are responsible for your project's
builds and packaging, please read on!

From:	John Arthorne/Ottawa/IBM@IBMCA
To:	cross-project-issues-dev@xxxxxxxxxxx
Date:	02/10/2009 09:49 AM
Subject:	[cross-project-issues-dev] Producing downloadable p2 repositories

---

If you are responsible for your project's builds and packaging, please
read on! 

As you all know, providing update sites that include p2 metadata is a "must
do" for the Galileo release. Now that everyone is producing this metadata,
the obvious question that arises is how do people building products and
packages consume this metadata? Everyone is accustomed to consuming Eclipse
project output in the convenient form of zip files:

* zips are easily replicated to company mirrors, which reduces bandwidth
costs for both producers and consumers 
* zips are a reliable and consistent input for builds. If you keep the
input zips around, you can reproduce an old build easily and reliably
* power users can hack together applications by unzipping various zips
into the Eclipse dropins folder 

However, there are also numerous advantages to consuming project output
in the form of p2 repositories: 

* Repositories can use pack200 to drastically reduce transfer costs and
disk footprint 
* Repositories contain p2 metadata that would otherwise need to be generated
on the fly by p2 on first startup 
* As projects start to produce and exploit more advanced p2 metadata, it
can no longer be generated on the fly (think chmod and sym-link metadata
for example) 
* A project can produce a single repository containing all of their project's
output. Consumers then have the flexibility to install only the portions
they need. In the past this consumer flexibility was only possible by having
the producer provide numerous zip files containing the different permutations
of their project output. These large collections of zips are a maintenance
nightmare for producers, and lead to slower builds and higher disk usage.

On the other hand, remote repositories don't make for a reliable build
input. They expose builds to transient communication failures, they may
change or be deleted, they are difficult to mirror, they add to bandwidth
costs if they are consumed remotely on every build, etc.

So, how do projects offer all of the advantages of both zips and p2 repositories?
The answer: zipped p2 repositories. Simply take the p2 repositories you
are producing today, zip them up, and make them available on your project
download page. Consumers can then download these repositories, and use
them offline in all the same ways they use either zips or remote repositories
today. The p2 team is now recommending this zipped repository format as
the downloadable format of the future. For more details, see this wiki
page: 

http://wiki.eclipse.org/Equinox/p2/Metadata_Consumption

Thanks, 
The p2 team_______________________________________________
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