On 11/16/2016 10:49 AM, Todor Boev wrote:
- Regarding resolver behavior:
The goal is actually to replace the behavior of the objective
function with the behavior of the resolver. This is the best way to
guarantee that both p2 and the OSGi runtime agree on what is a
consistent set of bundles. For example p2 does not take into account
package uses constraints which leads to p2 selecting bundles that
later fail to resolve at runtime. It does not matter which way to
resolve is better, so long as they agree. Since the OSGi resolver is
very unlikely to change it falls on p2 to match it's behavior. My
current company (software ag) has had quite a number of issues where
essentially p2 sets up the resolver to fail.
- Regarding resolver scalability:
The resolution is split between the resolver which processes the
current set of resources and the resolver context which selects
candidates when asked. If the goal is to support a very high number of
candidates - a resolver context impl optimized for searches in a large
candidate space can be provided. If the goal is to produce a solution
that includes a very high number of resources - more research is
required. Even if the initial set is 10,000 the resolver can be asked
to process them not all at once, but incrementally in batches or even
one by one. Which is in fact what equinox does today.
The thing is that if you look at a subset of the available bundles,
you may find a solution that is not the optimal one. p2 will consider
all the possible candidates in one resolution invocation.
I am trying to determine if it makes sense to invest effort in
prototyping this given that subtle changes in behavior are in fact a
goal, rather than an issue.
Even though on the surface p2 resolver looks similar to what the
OSGi resolver does, p2 has at least 2 additional concepts:
1) the expression of strict negation
2) the concept of patch
I'm tempted to think that it is probably simpler to add support for the
uses-clause in p2 (this has been a known issue for years, but I can't
seem to find the bug tonight) than it is to replace the resolver
completely and get all the tests to pass. The encoding of dependencies
to a SAT formula is well documented and so are the optimization functions.
On Wed, Nov 16, 2016 at 4:44 AM, Pascal Rapicault
<[email protected] <mailto:[email protected]>> wrote:
On 11/15/2016 12:52 PM, Todor Boev wrote:
Hello,
Are there any plans to bring together p2 and OSGi
resolver+repository standards?
There is no immediate plan for this.
It should be beneficial to have similar (maybe identical?)
dependency resolution at provisioning time and later at runtime.
The install time and runtime resolvers resolve a slightly
different problem because the install time resolver has to look
for candidates in a large space, whereas the runtime one has to
connect as many components together.
I have not tried replacing the p2 resolver with the new OSGi
resolver so I can't tell how it would perform.
Specifically:
- Is it possible to publish the bundle generic
capabilities/requirements to the p2 repository?
Yes this should be possible. The underlying p2 capability /
requirement model is really extensible and the current limitation
is only the serialized format.
- Is it possible to use the equinox Resolver inside the p2 Planner?
It is possible to get something going but I'm not sure if this
will scale (p2 resolver is able to perform seamlessly on 10's of
thousands of IUs), nor if you will be able to replicate the
subtleties that result from having an objective function.
- Even if the equinox Resolver can not be used is it possible
for p2 to handle generic requirements/capabilities?
Yes. This should not be too much work.
Regards,
Todor Boev
_______________________________________________
equinox-dev mailing list
[email protected] <mailto:[email protected]>
To change your delivery options, retrieve your password, or unsubscribe
from this list, visit
https://dev.eclipse.org/mailman/listinfo/equinox-dev
<https://dev.eclipse.org/mailman/listinfo/equinox-dev>
_______________________________________________ equinox-dev
mailing list [email protected]
<mailto:[email protected]> To change your delivery options,
retrieve your password, or unsubscribe from this list, visit
https://dev.eclipse.org/mailman/listinfo/equinox-dev
<https://dev.eclipse.org/mailman/listinfo/equinox-dev>
_______________________________________________
equinox-dev mailing list
[email protected]
To change your delivery options, retrieve your password, or unsubscribe from
this list, visit
https://dev.eclipse.org/mailman/listinfo/equinox-dev
_______________________________________________
equinox-dev mailing list
[email protected]
To change your delivery options, retrieve your password, or unsubscribe from
this list, visit
https://dev.eclipse.org/mailman/listinfo/equinox-dev
