Comment 3 for bug 1452468

Reviewed: https://review.openstack.org/180795
Committed: https://git.openstack.org/cgit/openstack/swift/commit/?id=666bf06c26bc9e0d6256d054835386e50e67b8a2
Submitter: Jenkins
Branch: master

commit 666bf06c26bc9e0d6256d054835386e50e67b8a2
Author: Samuel Merritt <email address hidden>
Date: Wed May 6 16:29:06 2015 -0700

    EC: don't 503 on marginally-successful PUT

    On EC PUT in an M+K scheme, we require M+1 fragment archives to
    durably land on disk. If we get that, then we go ahead and ask the
    object servers to "commit" the object by writing out .durable
    files. We only require 2 of those.

    When we got exactly M+1 fragment archives on disk, and then one
    connection timed out while writing .durable files, we should still be
    okay (provided M is at least 3). However, we'd take our M > 2
    remaining successful responses and pass that off to best_response()
    with a quorum size of M+1, thus getting a 503 even though everything
    worked well enough.

    Now we pass 2 to best_response() to avoid that false negative.

    There was also a spot where we were getting the quorum size wrong. If
    we wrote out 3 fragment archives for a 2+1 policy, we were only
    requiring 2 successful backend PUTs. That's wrong; the right number is
    3, which is what the policy's .quorum() method says. There was a spot
    where the right number wasn't getting plumbed through, but it is now.

    Change-Id: Ic658a199e952558db329268f4d7b4009f47c6d03
    Co-Authored-By: Clay Gerrard <email address hidden>
    Closes-Bug: 1452468