Bug 2043119

Summary: [OVN SCALE][ovn-northd] Incrementally process switch related load balancer changes
Product: Red Hat Enterprise Linux Fast Datapath Reporter: Dumitru Ceara <dceara>
Component: OVNAssignee: OVN Team <ovnteam>
Status: CLOSED WONTFIX QA Contact: Jianlin Shi <jishi>
Severity: unspecified Docs Contact:
Priority: high    
Version: FDP 21.KCC: ctrautma, jiji, mmichels
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Last Closed: 2023-07-28 17:21:57 UTC Type: Bug
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Bug Depends On: 2043116    
Bug Blocks: 2043128    
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Description Flags
Scale test NB database. none

Description Dumitru Ceara 2022-01-20 16:40:09 UTC 
Created attachment 1852238 [details]
Scale test NB database.

Description of problem:

In ovn-northd, the build_ovn_lbs() function does a few things
a. builds the map of load balancers, parsing the contents of the NB.Load_Balancer table
b. associates the resulting load balancers to all datapaths corresponding to the logical switches that refer to the NB.Load_Balancer (either directly or via the NB.Load_Balancer_Group) table.
c. reconciles the SB.Load_Balancer table.

For example, with the attached NB database (from a scale test run), build_ovn_lbs() takes ~650msec on the test machine, each and every time northd runs to process a change in the NB/SB.

We could try to extract this functionality in a separate I-P node with the following inputs:
- NB.Load_Balancer
- NB.Load_Balancer_Group
- SB.Load_Balancer
- Datapaths (depending on bug 2043116)

This node's data could serve as input to a flow-generation node, and would be used to generate all switch load balancer related logical flows.
Comment 1 Dumitru Ceara 2022-01-20 16:45:55 UTC 
> 
> We could try to extract this functionality in a separate I-P node with the
> following inputs:
> - NB.Load_Balancer
> - NB.Load_Balancer_Group
> - SB.Load_Balancer
> - Datapaths (depending on bug 2043116)
> 
> This node's data could serve as input to a flow-generation node, and would
> be used to generate all switch load balancer related logical flows.

On second thought, we probably need to split this in two different I-P nodes:

- one that computes ovn_northd_lb objects in general (new/updated/deleted)
- another one (that has as inputs: Datapaths, SB.Load_Balancer, NB.Load_Balancer_Group) and computes set of load balancers attached to each switch Datapath.
Comment 2 Mark Michelson 2022-01-20 18:06:10 UTC 
I think separating this into two nodes is a good idea, since there is the possibility that the output of both nodes could be useful separately.

Since there is a separate BZ for router-related LB changes (2043128), would it make sense to divide this BZ in two? This way, the first node that computes sets of general ovn_northd_lb can be done first, and then the switch- and router-related LB tasks could be done in parallel.
Comment 3 Mark Michelson 2023-07-28 17:21:57 UTC 
I'm closing this since northd load balancer I-P is being tracked in a different issue (and will be merged into OVN soon).