yahoo-eng-team team mailing list archive

[Don Bowman <don.waterloo+ubuntu@xxxxxxxxx>]

Public bug reported:

If I use heat to create a set of networks, each with its own subnet,
sometimes I will get an error from Neutron that there is an overlap.

There is an example heat template attached. In my environment, this will
fail about 1 or 2 times in 10.

The heat template does:

for X in seq 0 10
  create network X
  assign subnet 172.16.X.0/24 to network X

One of the stacks will get an error on one of the subnets, indicating:

Requested Subnet With Cidr: 172.16.7.0/24 For Network: 73f99807-0b2a-
49d3-8d11-B7bd74d02f4d Overlaps With Another Subnet.

This is in turn coming from _validate_subnet_cidr() in db/ipam_backend_mixin.py.
What is happening is that the 'new_subnet_cidr' passed in is matching against itself.

Since I have 'allow_overlapping_ips=true', it does:
subnet_list = network.subnets

but, in the failure case, this subnet is already there. In the 'no
failure case' it is not yet there.

I have 3 heat API servers, and 72 heat workers (3 servers). The api
servers are round-robin load balanced

I just (2016-06-24) reproduced this against the master/head from github
(so midway between mitaka and newton).

I'm not sure if there is some missing locking, but for sure this is a
race condition.

I have ipam_driver unset

If i comment out the exception in _validate_subnet_cidr() then it works
OK.

** Affects: neutron
     Importance: Undecided
         Status: New

** Attachment added: "Example heat template"
   https://bugs.launchpad.net/bugs/1596075/+attachment/4689902/+files/t.yml

-- 
You received this bug notification because you are a member of Yahoo!
Engineering Team, which is subscribed to neutron.
https://bugs.launchpad.net/bugs/1596075

Title:
  Neutron confused about overlapping subnet creation

Status in neutron:
  New

Bug description:
  If I use heat to create a set of networks, each with its own subnet,
  sometimes I will get an error from Neutron that there is an overlap.

  There is an example heat template attached. In my environment, this
  will fail about 1 or 2 times in 10.

  The heat template does:

  for X in seq 0 10
    create network X
    assign subnet 172.16.X.0/24 to network X

  One of the stacks will get an error on one of the subnets, indicating:

  Requested Subnet With Cidr: 172.16.7.0/24 For Network: 73f99807-0b2a-
  49d3-8d11-B7bd74d02f4d Overlaps With Another Subnet.

  This is in turn coming from _validate_subnet_cidr() in db/ipam_backend_mixin.py.
  What is happening is that the 'new_subnet_cidr' passed in is matching against itself.

  Since I have 'allow_overlapping_ips=true', it does:
  subnet_list = network.subnets

  but, in the failure case, this subnet is already there. In the 'no
  failure case' it is not yet there.

  I have 3 heat API servers, and 72 heat workers (3 servers). The api
  servers are round-robin load balanced

  I just (2016-06-24) reproduced this against the master/head from
  github (so midway between mitaka and newton).

  I'm not sure if there is some missing locking, but for sure this is a
  race condition.

  I have ipam_driver unset

  If i comment out the exception in _validate_subnet_cidr() then it
  works OK.

To manage notifications about this bug go to:
https://bugs.launchpad.net/neutron/+bug/1596075/+subscriptions