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



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
> 
> 
>