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[kolla][nova][neutron] Access to VMs is slow when running on a remote compute host


On Mon, 2019-07-15 at 16:29 +0200, Giuseppe Sannino wrote:
> Hi!
> first of all, thanks for the fast replies. I do appreciate that.
> 
> I did some more test trying to figure out the issue.
> - Set UseDNS to "no" in sshd_config  => Issue persists
> - Installed and configured Telnet => Telnet login is slow as well
> 
> From the "top" or "auth.log"nothing specific popped up. I can sshd taking
> some cpu for a short while but nothing more than that.
> 
> Once logged in the VM is not too slow. CLI doesn't get stuck or similar.
> One thing worthwhile to mention, it seems like the writing throughput on
> the disk is a bit slow: 67MB/s  wrt around 318MB/s of another VM running on
> a "datacenter" Openstack installation.
unless you see iowait in the guest its likely not related to the disk speed.
you might be able to improve the disk performace by changeing the chache mode
but unless you are seeing io wait that is just an optimisation to try later.

when you are logged into the vm have you tried ssh again via localhost to
determin if the long login time is related to the network or the vm.

if its related to the network it will be fast over localhost
if its related to the vm, e.g. because of disk, cpu load, memory load or ssh server configuration
then the local ssh will be slow.

> 
> The Cinder Volume docker is running on the Compute Host and Cinder is using
> the filesystem as backend.
> 
> BR
> /Giuseppe
> 
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> On Fri, 12 Jul 2019 at 17:41, Slawek Kaplonski <skaplons at redhat.com> wrote:
> 
> > Hi,
> > 
> > I suspect some problems with names resolving. Can You check if You have
> > also such delay when doing e.g. â??sudoâ?? commands after You ssh to the
> > instance?
> > 
> > > On 12 Jul 2019, at 16:23, Brian Haley <haleyb.dev at gmail.com> wrote:
> > > 
> > > 
> > > 
> > > On 7/12/19 9:57 AM, Giuseppe Sannino wrote:
> > > > Hi community,
> > > > I need your help ,tips, advices.
> > > > *> Environment <*
> > > > I have deployed Openstack "Stein" using the latest kolla-ansible on the
> > 
> > following deployment topology:
> > > > 1) OS Controller running as VM on a "cloud" location
> > > > 2) OS Compute running on a baremetal server remotely (wrt OS
> > 
> > Controller) location
> > > > 3) Network node running on the Compute host
> > > > As per the above info, Controller and compute run on two different
> > 
> > networks.
> > > > Kolla-Ansible is not really designed for such scenario but after
> > 
> > manipulating the globals.yml and the inventory files (basically I had to
> > move node specific network settings from the globals to the inventory
> > file), eventually the deployment works fine.
> > > > *> Problem <*
> > > > I have no specific issue working with this deployment except the
> > 
> > following:
> > > > "SSH connection to the VM is quite slow".
> > > > It takes around 20 seconds for me to log into the VM (Ubuntu, CentOS,
> > 
> > whatever).
> > > 
> > > But once logged-in things are OK?  For example, an scp stalls the same
> > 
> > way, but the transfer is fast?
> > > 
> > > > *> Observations <*
> > > >  * Except for the slowness during the SSH login, I don't have any
> > > >    further specific issue working with this envirorment
> > > >  * With the Network on the Compute I can turn the OS controller off
> > > >    with no impact on the VM. Still the connection is slow
> > > >  * I tried different type of images (Ubuntu, CentOS, Windows) always
> > > >    with the same result.
> > > >  * SSH connection is slow even if I try to login into the VM within the
> > > >    IP Namespace
> > > > From the ssh -vvv, I can see that the authentication gets stuck here:
> > > > debug1: Authentication succeeded (publickey).
> > > > Authenticated to *****
> > > > debug1: channel 0: new [client-session]
> > > > debug3: ssh_session2_open: channel_new: 0
> > > > debug2: channel 0: send open
> > > > debug3: send packet: type 90
> > > > debug1: Requesting no-more-sessions at openssh.com <mailto:
> > 
> > no-more-sessions at openssh.com>
> > > > debug3: send packet: type 80
> > > > debug1: Entering interactive session.
> > > > debug1: pledge: network
> > > > > > > > > 10 to 15 seconds later
> > > 
> > > What is sshd doing at this time?  Have you tried enabling debug or
> > 
> > running tcpdump when a new connection is attempted?  At first glance I'd
> > say it's a DNS issue since it eventually succeeds, the logs would help to
> > point in a direction.
> > > 
> > > -Brian
> > > 
> > > 
> > > > debug3: receive packet: type 80
> > > > debug1: client_input_global_request: rtype hostkeys-00 at openssh.com
> > 
> > <mailto:hostkeys-00 at openssh.com> want_reply 0
> > > > debug3: receive packet: type 91
> > > > debug2: callback start
> > > > debug2: fd 3 setting TCP_NODELAY
> > > > debug3: ssh_packet_set_tos: set IP_TOS 0x10
> > > > debug2: client_session2_setup: id 0
> > > > debug2: channel 0: request pty-req confirm 1
> > > > Have you ever experienced such issue ?
> > > > Any suggestion?
> > > > Many thanks
> > > > /Giuseppe
> > 
> > â??
> > Slawek Kaplonski
> > Senior software engineer
> > Red Hat
> > 
> >