[Bug 1642538] Re: swift-ring-builder rebalance - endless loop

[Corey Bryant]

This has been uploaded to zesty, as well as the yakkety and xenial
review queues where packages are  awaiting SRU team review.

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https://bugs.launchpad.net/bugs/1642538

Title:
  swift-ring-builder rebalance - endless loop

Status in Ubuntu Cloud Archive:
  Triaged
Status in Ubuntu Cloud Archive mitaka series:
  Fix Committed
Status in Ubuntu Cloud Archive newton series:
  Triaged
Status in Ubuntu Cloud Archive ocata series:
  Triaged
Status in OpenStack Object Storage (swift):
  Fix Released
Status in swift package in Ubuntu:
  Triaged
Status in swift source package in Xenial:
  Triaged
Status in swift source package in Yakkety:
  Triaged
Status in swift source package in Zesty:
  Triaged

Bug description:
  There is an issue with swift-ring-builder and rebalancing under
  certain conditions beginning in Mitaka.

  Steps to reproduce:
  Create a ring with part power of 12. 3 servers with 11 devices each, BUT 2 servers in zone 1 and one server in zone 2. After adding all devices as described above, swift-ring-builder <ring>.builder rebalance does not return and seems to run into an endless loop.

  The weirdness starts with the 11th device, 10 devices still work. It
  does not matter whether you add each 10 devices from the 3 servers and
  rebalance, and than add the 11th device from each server afterwards or
  do it all at once.

  This behaviour does not exists in Liberty and starts with Mitaka.

  For connivence I am adding the statements to reproduce:


  swift-ring-builder account.builder create 12 3 1

  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-01 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-02 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-03 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-04 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-05 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-06 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-07 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-08 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-09 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-10 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.60 --port 6002 --replication-ip 10.46.15.60 --replication-port 6002 --device swift-11 --weight 100.00

  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-01 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-02 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-03 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-04 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-05 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-06 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-07 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-08 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-09 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-10 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 1 --ip 10.46.15.61 --port 6002 --replication-ip 10.46.15.61 --replication-port 6002 --device swift-11 --weight 100.00

  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-01 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-02 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-03 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-04 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-05 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-06 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-07 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-08 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-09 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-10 --weight 100.00
  swift-ring-builder account.builder add --region 1 --zone 2 --ip 10.46.15.62 --port 6002 --replication-ip 10.46.15.62 --replication-port 6002 --device swift-11 --weight 100.00

  swift-ring-builder account.builder rebalance

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