Hi David,
For the meta-data, order doesn't matter since that would break the
whole idea of using a SAT algorithm to come up with a resolution. p2
will build a set of all UI's in the repository (composite or not),
and then feed that to the SAT solver. The solver then comes up with
a plan. The order of children doesn't affect the content of the set.
For the artifacts, I know that url's with 'file:' are consulted
first so that unnecessary download traffic is avoided. I'm almost
certain that with the 'file' priority out of the way, the artifact
repositories are consulted in the order they are listed.
Regards,
Thomas Hallgren
On 2011-02-19 08:01, David M Williams wrote:
In particular, is it
part of the "spec"
or API? (That is, I'm not just asking about current
implementation).
I think this issue will become
more
relevant, especially for eclipse.org, now that p2 is getting
"old"
:) because some repos that were on 'downloads' should at some
point
move to 'archives'.
Let me elaborate. In a composite
repo,
many of us might have child repos that might be similar to the
following
fictional URLs ...
<children size='3'>
<child
location='http://archive.eclipse.org/webtools/R3.2.0/'
/>
<child
location='http://archive.eclipse.org/webtools/R3.2.1/'
/>
<child
location='http://download.eclipse.org/webtools/R3.2.2/'
/>
</children>
Is that order, above, treated differently
than the
order, below? Which repo is searched (or matched) first for
artifacts?
<children size='3'>
<child
location='http://download.eclipse.org/webtools/R3.2.2/'
/>
<child
location='http://archive.eclipse.org/webtools/R3.2.1/'
/>
<child
location='http://archive.eclipse.org/webtools/R3.2.0/'
/>
</children>
This can become important, for
example,
if some artifact is the same in all three repositories ....
that is, the
version/qualifier is unchanged. If the "archive" repos are
tried
first, then the result would not be mirrored, and always come
from eclipse.org
directly, it seems. The opposite would be desired, that
'downloads' repos
would be "searched/matched" first, and if found there, then,
via the magic of the mirrors URL, would have a chance of
coming from a
mirror, thus being faster for many users (and off-loading some
bandwidth
from eclipse.org).
So, is there a way to make sure
'download'
URLs are matched first? Should they come first in list, or
last ... or
is the outcome indeterminable?
Any advice?
Feel free to comment in bug
330134 ...
which was opened some time ago to "investigate" this issue ...
but, I'm hoping some p2 expert knows the answer, and I won't
have to investigate
:)
https://bugs.eclipse.org/bugs/show_bug.cgi?id=330134
Thanks,
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