vm cannot be created after a large number of vms are removed from the same node

[ZhouHeng]

vm cannot be created after a large number of virtual machines are removed from the same node

1、create a security group, has remote security group rule
2、create 50 vms in same node(eg: node01) and use same security group created in step 1
3、delete all vms created in step 2
4、create some vms in nodeo1
5、all vms create failed. error is: Build instance <id> aborted: Failed to allocate the network(s), ...

By observing the database when creating the vm, it is found that port's L2 block has not been removed.

[Lajos Katona (lajos-katona)]

Thanks for the bug report, could you please give some details, like:
* opsntack version
* firewall driver (ovs, hybrid....)

[Lajos Katona (lajos-katona)]

I tried to reproduce on master with firewall_driver = openvswitch, and as I used devstack I had only ~15 VMs on my compute, and for me there was no problem after deleting the VMs and creating new ones after.

By the way I created my VMs one-by-one.

[ZhouHeng (zhouhenglc)]

firewall_driver = OVSHybridIptablesFirewallDriver
15 VMs are too few.
step 1 must not be less.
The main reason for this problem is that when deleting a large number of vms, a large number of ip conntrack need to be deleted, which will occupy CPU and rpc_loop cannot execute.

[Launchpad Janitor (janitor)]

[Expired for neutron because there has been no activity for 60 days.]