[ovs-dev] OVN: proposal of introducing nlog engine to ovn-northd

[Yusheng Wang]

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We are trying to propose a new computation model for the ovn-northd application. Currently, ovn-northd computes all logical data path flows for every change. This full computation model is simple and helped verifying the concept of logical data path design, but it also suffers performance drawback.

?In order to move from full computation to incremental computation, more sophisticated tool is needed to manage the complexity associated with both generating more and more complex logical data path flows and dealing with irrelevant sequence of incremental changes.

Now we think it is good time to introduce the new computation model - nlog. Nlog is a specialized declarative programming language based on datalog.

The nlog computation model has been proved to work well for quite a few systems. We have done a POC in which a brand new nlog compiler and nlog run-time engine are implemented. Nlog program has been written to implement basic ovn features to verify its capabilities.

?We see a good match of the ovn data schema with nlog computation model. Both ovn-northd and ovn-controller use ovsdb and the data to be processed are tuples. This is also true for nlog programs and minimum data transformation is needed to adapt to the new computation model.

?This move will take multiple phases and current ovn-northd functionality will not be impacted. The north and south side database schema will not be changed during and after this move.

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