NSE Composition: Registry should be able to match labels from NSE label as from list of labels

[Bolodya1997]

Overview

Registry should be able to match labels from NSE label as from list of labels:

NSE-1:  label=one
NSE-2:  label=two
NSE-12: label=one,two

find:   label=one
result: { NSE-1, NSE-12 }

find:   label=two
result: { NSE-2, NSE-12 }

References

• select NSEs from memory registry by query -

  sdk/pkg/registry/common/memory/nse_server.go

  Line 111 in 79914fd

  if matchutils.MatchNetworkServiceEndpoints(query.NetworkServiceEndpoint, nse) {

• select NSEs from k8s registry by query - https://github.com/networkservicemesh/sdk-k8s/blob/c5dac67b50b69c78dedf559391d31ce464cd8932/pkg/registry/etcd/nse_server.go#L84
• corresponding method in matchutils -

  sdk/pkg/tools/matchutils/utils.go

  Line 37 in 79914fd

  func MatchNetworkServiceEndpoints(left, right *registry.NetworkServiceEndpoint) bool {

Tests

1. Unit tests in matchutils.
2. Sandbox test (would be nice to create for both memory, k8s registries):
   1. add endpoint with list label (label=one,two)
   2. request NS with simple label (label=one)

[d-uzlov]

@edwarnicke
If we implement this, NSE labels will effectively become arrays of labels, packed into a string. It makes sense to change the API to have labels be arrays.
Do you approve such change in the API?

[edwarnicke]

@d-uzlov I don't understand why this implies labels being an array packed as a string...

[d-uzlov]

Well, if the description in this issue is correct, then "label=one,two should match both label=one and label=two" looks pretty much like "label should be considered an array, and label=<value> should match any endpoint which label contains <value> in it".
That is: if the description in this issue is correct. If it is not, we should probably discuss it in the parent issue.

[edwarnicke]

I think there's discussion to be had in the parent issue.

[Bolodya1997]

Don't actually needed because instead of doing this:

step: 1 -> step: 2
step: 3 -> step: 4

nse-1: { step: 1,3 } 
nse-2: { step: 2 }
nse-3: { step: 4 }

we can do that:

step: 1 -> step: 2
labe: a -> labe: b

nse-1: { step: 1, labe: a } 
nse-2: { step: 3 }
nse-3: { labe: b }