[openstack-dev] Fwd: Chalenges with highly available service VMs

Aaron Rosen arosen at nicira.com
Thu Jul 4 21:33:11 UTC 2013

[Moving to list]

Hi Sam,

responses inline

---------- Forwarded message ----------
From: Samuel Bercovici <SamuelB at radware.com>
Date: Thu, Jun 27, 2013 at 1:43 PM
Subject: Chalenges with highly available service VMs
To: "Mark McClain (mark.mcclain at dreamhost.com)" <mark.mcclain at dreamhost.com>,
"arosen at nicira.com" <arosen at nicira.com>
Cc: Samuel Bercovici <SamuelB at radware.com>, Avishay Balderman <
AvishayB at radware.com>, "gary.kotton at gmail.com" <gary.kotton at gmail.com>, "
gkotton at redhat.com" <gkotton at redhat.com>


** **

As part of provisioning load balancer service VMs we have encountered the
following changes.****

Our planned HA model for this release is going to use a strategy in which
IP addresses are configured on the HA VM pair in the same way but only the
active box is “connected” to the network and answers ARP request.****

When the 1st VM fails and after the 2nd VM detects this, it will do a GARP
and will take ownership on the IP addresses.****

The assumption is the underlying L2 network can support IP to MAC discovery.


*[arosen] - yup makes sense. *

The challenge that we are facing is that currently each Neutron port,
automatically gets “security” protection via IP tables which is intended to
prevent IP spoofing. ****

If the load balancer service VM gets configured with an IP (ex: VIP) this
security blocks traffic to the IP until the Neutron port gets updated with
this addition IP.****

In addition the IP should be allocated/marked as used in a Neutron subnet
and currency AFAIK there is no means to allocate an IP address without
attaching it to a Neutron port.****

I do not know how a network based on Nicira behaves as AFAIK it does not
use IP tables.****

** **

In the case of 2 machines acting as an HA pair the same IP address needs to
be assigned to two Neutron ports so that the IP tables rules will be update
correctly for bot. AFAIK this (IP attached to two Neutron Pots) is
currently not supported.****

As I expect that get 10s-100s VIPs mapped to the same Neutron port, I am
worried that having many rules in a chain will have an impact.****

** **

Follows a few options to solve this:****

**1.     **Define a Neutron port as a Neutron service port. In this case
the assumption is that the VM/Port belongs to the cloud infrastructure and
hence no need to specify the IP tables rules that prevents “MAC” spoofing
or “IP” spoofing (which are some of the different strategies to achieve
HA). Potentially add support in Nova so that when a VM marked as service VM
in nova is provisioned, than the Neutron ports of this VM will be defines
as Neutron service ports.****

*[arosen] - there is already an extension that does this though only the
nvp plugin implements it at the time though it shouldn't be very hard to
add support for it in other plugins. *

**2.     **Add support for assigning the same IP address to two Neutron

[arosen] - there is a blueprint for pluggable ipam which might work for
this.  That said. it seems like it might also be worth while to add an
extension that allows you to add/remove ip/mac address pairs to a port.


What do you think?****

** **



** **
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