Bug 275217 – sys-apps/portage: implement backtracking for slot conflicts

• Product: Portage Development
• Status: RESOLVED FIXED

[Description Sebastian Luther (few) 2009-06-23 19:56:19 UTC]

Another tale in the quest for a easier to follow portage code.

[Comment 1 Sebastian Luther (few) 2009-06-23 19:57:40 UTC]

Created attachment 195594 [details, diff]
resolve the circular dep between Scheduler and depgraph; mark all functions as local that aren't used outside of depgraph

[Comment 2 Sebastian Luther (few) 2009-06-23 20:17:06 UTC]

Created attachment 195595 [details, diff]
move changelog stuff stuff out of depgraph (needs changelog.py)

[Comment 3 Sebastian Luther (few) 2009-06-23 20:17:33 UTC]

Created attachment 195597 [details, diff]
changelog.py for part2

[Comment 4 Zac Medico 2009-06-23 20:45:14 UTC]

(In reply to comment #1)
> Created an attachment (id=195594) [edit]
> resolve the circular dep between Scheduler and depgraph; mark all functions as
> local that aren't used outside of depgraph

Thanks, this is in svn r13676.

(In reply to comment #2)
> Created an attachment (id=195595) [edit]
> move changelog stuff stuff out of depgraph (needs changelog.py)

Thanks, this is in svn r13677.

[Comment 5 Sebastian Luther (few) 2009-06-24 11:38:00 UTC]

Created attachment 195653 [details, diff]
splits depgraph.select_files into select_files and _resolve

In the long term all decision making shall be made in _resolve. select_files converts its input to args and _resolve uses the args to pull in the root nodes now.

[Comment 6 Zac Medico 2009-06-24 21:08:15 UTC]

(In reply to comment #5)
> Created an attachment (id=195653) [edit]
> splits depgraph.select_files into select_files and _resolve

Thanks, this is in svn r13685.

[Comment 7 Sebastian Luther (few) 2009-06-30 21:49:54 UTC]

Created attachment 196212 [details, diff]
Move all memeber variables of _emerge.depgraph into frozen_config or dynamic_config.

This patch creates two classes in _emerge/depgraph.py: _frozen_depgraph_config and _dynamic_depgraph_config. They are supposed to hold all member variables of _emerge.depgraph. Those that may change after initialization belong to _dynamic_depgraph_config, others to _frozen_depgraph_config. depgraph itself holds only instances of these two classes.

[Comment 8 Zac Medico 2009-06-30 22:06:46 UTC]

(In reply to comment #7)
> Created an attachment (id=196212) [edit]
> Move all memeber variables of _emerge.depgraph into frozen_config or
> dynamic_config.

Thanks, this is in svn r13747.

[Comment 9 Sebastian Luther (few) 2009-07-01 19:28:27 UTC]

Just for reference:

What is left? 
1) Write wrapper functions for _dynamic_config to track changes to it.
2) Write a function that searches the point where offending packages were selected and reverts the dynamic_config to this point.
3) Write a function that figures out what to mask if something goes wrong.
4) modify _resolve to be somehow state less, so we can simply restart from any state.

[Comment 10 Zac Medico 2009-07-03 00:04:20 UTC]

As discussed on irc, the simplest way implement backtracking (at least initially) is to try saving choices from depgraph, and then creating a whole new depgraph with slightly different choices. Right now I'm working on making the depgraph constructor take a _frozen_depgraph_config instance as a parameter, so that we can use a single instance for each depgraph we create.

[Comment 11 Zac Medico 2009-07-03 01:33:08 UTC]

(In reply to comment #10)
> Right now I'm working on making
> the depgraph constructor take a _frozen_depgraph_config instance as a
> parameter, so that we can use a single instance for each depgraph we create.

This is done in svn r13760, and it's used to optimize resume_depgraph() in r13761.

[Comment 12 Zac Medico 2009-07-03 03:35:11 UTC]

I looked at your backtracking patch with the _pref_list_lookup() function and I think that it would be better to use an approach similar to the one used to solve bug #253904, in which _dep_check_composite_db._visible() is used to influence the behavior of dep_zapdeps(). When a package is masked by _dep_check_composite_db._visible(), it appears to dep_zapdeps() that the package is unavailable, and so any choice which pulls in that package will be avoided.

[Comment 13 Sebastian Luther (few) 2009-07-03 21:32:58 UTC]

Created attachment 196543 [details, diff]
Make emerge mask the first package pulled into the tree in case of a slot conflict and restart the dependency calculation

[Comment 14 Zac Medico 2009-07-04 05:34:48 UTC]

(In reply to comment #13)
> Created an attachment (id=196543) [edit]
> Make emerge mask the first package pulled into the tree in case of a slot
> conflict and restart the dependency calculation

Thanks, that's in svn r13769. I added some additional features:

 * display message about missed updates
 * cache frozen_config instance, to optimize performance
 * disable backtracking if it fails, fall back to a normal

[Comment 15 Zac Medico 2009-08-03 23:08:53 UTC]

This is fixed in 2.2_rc34.

[Comment 16 Zac Medico 2009-08-05 20:40:20 UTC]

Reopening until this is an unmasked release.

[Comment 17 Zac Medico 2009-10-11 00:49:26 UTC]

This is fixed in 2.1.7.