[Bug 1782300] Re: COLO unable to failover to secondary VM

[Thomas Huth]

The QEMU project is currently considering to move its bug tracking to another 
system. For this we need to know which bugs are still valid and which could be 
closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state 
back to "New" within the next 60 days, otherwise this report will be marked as 
"Expired". Or mark it as "Fix Released" if the problem has been solved with a 
newer version of QEMU already. Thank you and sorry for the inconvenience.

** Changed in: qemu
       Status: New => Incomplete

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Title:
  COLO unable to failover to secondary VM

Status in QEMU:
  Incomplete

Bug description:
  I test COLO feature on my host following docs/COLO-FT.txt in qemu folder, but 
fail to failover to secondary VM. 
  Is there any mistake in my execution steps?

  Execution environment:
  QEMU v2.12.0-rc4
  OS:     Ubuntu 16.04.3 LTS
  Kernel: Linux 4.4.35
  Secondary VM IP: noted as "a.b.c.d"

  Execution steps:
  # Primary
  ${COLO_PATH}/x86_64-softmmu/qemu-system-x86_64 \
      -enable-kvm \
      -m 512M \
      -smp 2 \
      -qmp stdio \
      -vnc :7 \
      -name primary \
      -device piix3-usb-uhci \
      -device usb-tablet \
      -netdev tap,id=tap0,vhost=off \
      -device virtio-net-pci,id=net-pci0,netdev=tap0 \
      -drive 
if=virtio,id=primary-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,\
          children.0.file.filename=${IMG_PATH},\
          children.0.driver=raw -S

  # Secondary
  ${COLO_PATH}/x86_64-softmmu/qemu-system-x86_64 \
      -enable-kvm \
      -m 512M \
      -smp 2 \
      -qmp stdio \
      -vnc :8 \
      -name secondary \
      -device piix3-usb-uhci \
      -device usb-tablet \
      -netdev tap,id=tap1,vhost=off \
      -device virtio-net-pci,id=net-pci0,netdev=tap1 \
      -drive 
if=none,id=secondary-disk0,file.filename=${IMG_PATH},driver=raw,node-name=node0 
\
      -drive if=virtio,id=active-disk0,driver=replication,mode=secondary,\
          file.driver=qcow2,top-id=active-disk0,\
          file.file.filename=$ACTIVE_DISK,\
          file.backing.driver=qcow2,\
          file.backing.file.filename=$HIDDEN_DISK,\
          file.backing.backing=secondary-disk0 \
      -incoming tcp:0:8888

  # Enter into Secondary:
  {'execute':'qmp_capabilities'}
  { 'execute': 'nbd-server-start',
      'arguments': {'addr': {'type': 'inet', 'data': {'host': 'a.b.c.d', 
'port': '8889'} } }
  }
  {'execute': 'nbd-server-add', 'arguments': {'device': 'secondary-disk0', 
'writable': true } }

  # Enter into Primary:
  {'execute':'qmp_capabilities'}
  {'execute': 'human-monitor-command',
      'arguments': {
          'command-line': 'drive_add -n buddy 
driver=replication,mode=primary,file.driver=nbd,file.host=a.b.c.d,file.port=8889,file.export=secondary-disk0,node-name=nbd_client0'
      }
  }
  { 'execute':'x-blockdev-change', 'arguments':{'parent': 'primary-disk0', 
'node': 'nbd_client0' } }
  { 'execute': 'migrate-set-capabilities',
      'arguments': {'capabilities': [ {'capability': 'x-colo', 'state': true } 
] } }
  { 'execute': 'migrate', 'arguments': {'uri': 'tcp:a.b.c.d:8888' } }

  # To test failover
  Primary
  { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'primary-disk0', 
'child': 'children.1'}}
  { 'execute': 'human-monitor-command','arguments': {'command-line': 'drive_del 
nbd_client0'}}

  Secondary
  { 'execute': 'nbd-server-stop' }

  Stop Primary
  Send ^C signal to terminate PVM.

  Secondary
  { "execute": "x-colo-lost-heartbeat" }

  
  # Result:
  Primary (Use ^C to terminate)
  qemu-system-x86_64: Can't receive COLO message: Input/output error
  qemu-system-x86_64: terminating on signal 2
  {"timestamp": {"seconds": 1531815575, "microseconds": 997696}, "event": 
"SHUTDOWN", "data": {"guest":false}}

  Secondary
  { 'execute': 'nbd-server-stop' }
  {"return": {}}
  { "execute": "x-colo-lost-heartbeat" }
  {"return": {}}
  qemu-system-x86_64: Can't receive COLO message: Input/output error
  Segmentation fault

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