osd: PeeringState: fix selection order in calc_replicated_acting_stretch

[gregsfortytwo]

We were previously mis-ordering these to deprioritize the existing acting set. That is bad!

We generate OSD candidates from the acting set and strays, and push
them into the candidates list as a tuple of <<!in_acting,pg_info.last_update>,osd_id>.

Then we sort the list. Then we go through the list from front to back and
push_back entries into the appropriate ancestor lists.

And then we pop_back() off the lists to select the acting set.
Which of course turns our nice careful order backwards! So don't do that.

Fixes: https://tracker.ceph.com/issues/53824

Signed-off-by: Greg Farnum gfarnum@redhat.com

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[gregsfortytwo]

Our lack of upstream tests around stretch mode is a problem here: I don't really see how to properly test this except giving it to the folks who have seen it (Red Hat QE; thanks guys!). So I think we just do our due diligence that it doesn't break the suite and then merge it in.

[gregsfortytwo]

No patch changes, just rebased to latest master since the doc and make check both failed on not-my-code?

[neha-ojha]

jenkins test api

[neha-ojha]

Our lack of upstream tests around stretch mode is a problem here: I don't really see how to properly test this except giving it to the folks who have seen it (Red Hat QE; thanks guys!). So I think we just do our due diligence that it doesn't break the suite and then merge it in.

what kind of test scenario uncovered this bug?

[yuriw]

jenkins test api

[yuriw]

jenkins test api

[neha-ojha]

jenkins test api

[ljflores]

The failed api test showed this line: Building remotely on 172.21.2.12+braggi12 indicating that it was running on braggi12. There was an issue with braggi12 in the past, but it was fixed by David Galloway so not entirely sure it was the same thing.

In any case, we'll see if it passes now.