[openstack-dev] [nova] Pike PTG recap - cells

Balazs Gibizer balazs.gibizer at ericsson.com
Tue Feb 28 09:46:52 UTC 2017

On Tue, Feb 28, 2017 at 3:10 AM, Zhenyu Zheng 
<zhengzhenyulixi at gmail.com> wrote:
> Matt,
> Thanks for the recap, it's a pity I cannot attend PTG due to personal 
> reason, I will be willing to take the work you mentioned, and will 
> check the details with you.
> And another thing, I don't know whether you guys discussed or not, I 
> saw in [1] we are talking about adding tags field(and others of 
> cause) to the instance notification
> payload, to be able to send during instance.create and 
> instance.update. The fact is that currently we cannot add tags during 
> boot, nor we send notifications when we
> add/update/delete tags latter(it is a direct DB change and no 
> instance.update notification has been sent out), so for tags field, 
> we have to wait for another instance.update
> action to get the latest info. And I have already tried to working on 
> the boot thing[2] and already planned to work on the tag notification 
> thing[3].
> So, are there any plans about those? Maybe it is OK to send out 
> instance.update notification in tags actions once [1] got merged?


The [1] was shortly discussed and agreed that it is high priority for 
Pike. The basic things in that bp have code up for review [4] so we 
have a good chance to merge it in early Pike. The BDM part of [1] needs 
some data modeling work still.

I did an initial review round on [3] and left some question in the spec.



> Thanks,
> Kevin Zheng
> [1] 
> https://blueprints.launchpad.net/nova/+spec/additional-notification-fields-for-searchlight
> [2] 
> https://blueprints.launchpad.net/nova/+spec/support-tag-instance-when-boot
> [3] https://blueprints.launchpad.net/nova/+spec/send-tag-notification
> On Tue, Feb 28, 2017 at 6:33 AM, Matt Riedemann <mriedemos at gmail.com> 
> wrote:
>> We talked about cells on Wednesday morning at the PTG. The full 
>> etherpad is here [1].
>> Searchlight integration
>> -----------------------
>> We talked a bit about what needs to happen for this, and it starts 
>> with getting the data into searchlight so that it can serve the REST 
>> API, which is being worked in this blueprint [2]. We want to get 
>> that done early in Pike.
>> We plan on making the use of Searchlight configurable in Nova since 
>> at first you might not even have anything in it, so listing 
>> instances wouldn't work. We're also going to attempt to merge-sort 
>> when listing instances across multiple cells but it's going to be a 
>> known issue that it will be slow.
>> For testing Nova with Searchlight, we need to start by enabling the 
>> Searchlight devstack plugin in the nova-next CI job, which I'll work 
>> on.
>> I'm going to talk to Kevin Zheng about seeing if he can spend some 
>> time on getting Nova to use Searchlight if it's (1) configured for 
>> use and (2) is available (the endpoint is in the service catalog). 
>> Kevin is a Searchlight core and familiar with the Nova API code, so 
>> he's a good candidate for working on this (assuming he's available 
>> and willing to own it).
>> Cells-aware gaps in the API
>> ---------------------------
>> Dan Smith has started a blueprint [3] for closing gaps in the API 
>> which break in a multi-cell deployment. He has a test patch [4] to 
>> expose the failures and then they can be worked on individually. The 
>> pattern of the work is in [5]. Help is welcome here, so please 
>> attend the weekly cells meeting [6] if you want to help out.
>> Auto-discovery of compute hosts
>> -------------------------------
>> The "discover_hosts_in_cells_interval" config option was introduced 
>> in Ocata which controls a periodic task in the scheduler to discover 
>> new unmapped compute hosts but it's not very efficient since it 
>> queries all cell mappings and then all compute nodes in each cell 
>> mapping and checks to see if those compute nodes are yet mapped to 
>> the cell in the nova_api database. Dan Smith has a series of changes 
>> [7] which should make that discovery process more efficient, it just 
>> needs to be cleaned up a bit.
>> Service arrangement
>> -------------------
>> Dan Smith is working on a series of changes in both Nova and 
>> devstack for testing with multiple cells [8]. The general idea is 
>> that there will still be two nodes and two nova-compute services. 
>> There will be three nova-conductor services, one per cell, and then 
>> another top-level "super conductor" which is there for building 
>> instances and sending the server create down to one of the cells. 
>> All three conductors are going to be running in the subnode just to 
>> balance the resources a bit otherwise the primary node is going to 
>> be starved. The multi-cell job won't be running migration tests 
>> since we don't currently support instance move operations between 
>> cells. We're going to work a hack into the scheduler to restrict a 
>> move operation to the same cell the instance is already in. This 
>> means the live migration job will still be a single-cell setup where 
>> both nova-computes are in the same cell.
>> Getting rid of nova-consoleauth
>> -------------------------------
>> There is an unfinished blueprint [9] from Paul Murray which melwitt 
>> is going to pick up for Pike. The idea is to move the tokens into 
>> the database so we don't care where the consoleauth service lives 
>> and then we can also kill the service.
>> [1] https://etherpad.openstack.org/p/nova-ptg-pike-cells
>> [2] 
>> https://blueprints.launchpad.net/nova/+spec/additional-notification-fields-for-searchlight
>> [3] https://blueprints.launchpad.net/nova/+spec/cells-aware-api
>> [4] https://review.openstack.org/#/c/433318/
>> [5] https://review.openstack.org/#/c/433362/
>> [6] http://eavesdrop.openstack.org/#Nova_Cellsv2_Meeting
>> [7] https://review.openstack.org/#/c/427901/
>> [8] https://review.openstack.org/#/c/436094/
>> [9] 
>> https://blueprints.launchpad.net/nova/+spec/convert-consoles-to-objects
>> --
>> Thanks,
>> Matt Riedemann
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