+++ This bug was initially created as a clone of Bug #981729 +++

--- Additional comment from Alex Jia on 2014-02-25 11:18:06 CET ---

Daniel, I can successfully start 41 containers not 40 now, is it an expected result? 

# tail -3 /etc/libvirt/libvirtd.conf 
max_clients = 20
max_workers = 20
max_queued_clients = 20

# for i in {1..50}; do virt-sandbox-service create -C -u httpd.service -N dhcp myapache$i;done

# for i in {1..50}; do virsh -c lxc:/// start myapache$i & done

# virsh -c lxc:/// -q list |wc -l
41

# rpm -q libvirt-daemon libvirt-sandbox kernel
libvirt-daemon-1.1.1-23.el7.x86_64
libvirt-sandbox-0.5.0-9.el7.x86_64
kernel-3.10.0-86.el7.x86_64

Additional info:

error: Failed to start domain myapache36
error: internal error: Failed to allocate free veth pair after 10 attempts

error: Failed to start domain myapache29
error: internal error: Failed to allocate free veth pair after 10 attempts

NOTE: Maybe, 10 attempts are too few for some users then they possibly want to change this, so I think it will be better if we have a configuration item for it, otherwise, we should document 10 attempts in libvirtd.conf or relevant guide.

--- Additional comment from Michal Privoznik on 2014-02-25 16:51:28 CET ---

(In reply to Alex Jia from comment #10)
> Daniel, I can successfully start 41 containers not 40 now, is it an expected
> result? 
> 
> # tail -3 /etc/libvirt/libvirtd.conf 
> max_clients = 20
> max_workers = 20
> max_queued_clients = 20
> 
> # for i in {1..50}; do virt-sandbox-service create -C -u httpd.service -N
> dhcp myapache$i;done
> 
> # for i in {1..50}; do virsh -c lxc:/// start myapache$i & done
> 
> # virsh -c lxc:/// -q list |wc -l
> 41

Yes and no. Kernel does some caching on sockets and some partial opening even if the server is not currently responsive too. So you may end up with more than 40 guests running. Hence I think anything above or equal to 40 is okay.

> 
> # rpm -q libvirt-daemon libvirt-sandbox kernel
> libvirt-daemon-1.1.1-23.el7.x86_64
> libvirt-sandbox-0.5.0-9.el7.x86_64
> kernel-3.10.0-86.el7.x86_64
> 
> Additional info:
> 
> error: Failed to start domain myapache36
> error: internal error: Failed to allocate free veth pair after 10 attempts
> 
> error: Failed to start domain myapache29
> error: internal error: Failed to allocate free veth pair after 10 attempts
> 

This is an internal (buggy) implementation. Let me see if I can fix this.

--- Additional comment from Michal Privoznik on 2014-02-25 17:08:22 CET ---

Patch proposed upstream:

https://www.redhat.com/archives/libvir-list/2014-February/msg01548.html

--- Additional comment from Michal Privoznik on 2014-02-26 10:07:51 CET ---

Moving to POST:

http://post-office.corp.redhat.com/archives/rhvirt-patches/2014-February/msg00829.html