Use dns target for urls in interdomain and floating interdomain scenarious

[denis-tingaikin]

Overview

Currently, we're using '@' to determine is the network service or network service endpoint related to the some another (external) domain.

For example,

my-service@my-domain means that my-service is located in the remote domain my-domain.

This is working fine, but we could try to support dns target pattern from the grpc.

dns:[//authority/]host[:port] – DNS (default)

1. host is the host to resolve via DNS.
2. port is the port to return for each address. If not specified, 443 is used (but some implementations default to 80 for insecure channels).
3. authority indicates the DNS server to use, although this is only supported by some implementations. (In C-core, the default DNS resolver does not support this, but the c-ares based resolver supports specifying this in the form "IP:port".)

Source: https://grpc.github.io/grpc/core/md_doc_naming.html

Example

At this moment endpoint entries in the registry are

name: nse-1
url: "tcp://${nsmgr-proxy-ip-address}"

With this feature we'll able to use this

name: nse-1
url: "dns://${my-own-dns-server}/${nsmgr-proxy-service-name}"

Pros/cons

Pors:

1. Use tested standard from the grpc
2. Add an option to use custom DNS servers in the interdomain tests.
3. Simplify the system (we dont need extra mapping or registry-proxy component)
4. Do not need to add dns proxying in interdomain examples (in other words we could super simplify this https://github.com/networkservicemesh/deployments-k8s/tree/main/examples/multicluster/usecases/interdomain_dns

Cons:

1. Backward compatibility

References

https://networkservicemesh.io/docs/concepts/k8s/

Decomposition

• Rework swapIP chain element and its tests ~ 4h
• Rework dnsdiscover chain element and its tests ~ 4h
• Reowork sandbox testing ~ 4h
• Stabilize interdomain sandbox test~ 4h
• Stabilize floating interdomain sandbox test~ 4h
• Rework interdomain dns example~ 4h
• Rework floating interdomain dns example~ 4h
• Rework monolith dns example~ 4h
• Risks

[denis-tingaikin]

@edwarnicke What do you think?

[denis-tingaikin]

@edwarnicke

FYI: I've added diagrams for clarificaitons https://drive.google.com/file/d/1dYbECvp6Et8W2kIbQzc8RjJSpI7g5qCX/view?usp=sharing

Also this ticket allows to do not go ahead with registry proxy

Closes: networkservicemesh/cmd-registry-proxy#1
Closes networkservicemesh/deployments-k8s#9318
Closes networkservicemesh/deployments-k8s#8343
Closes networkservicemesh/deployments-k8s#10221

[edwarnicke]

@denis-tingaikin Could you point me to the current URI standard we are using that you are proposing replacing? I'd like to make sure we are covering all the cases reasonably.

[denis-tingaikin]

@edwarnicke I've implemented this based on https://grpc.github.io/grpc/core/md_doc_naming.html without any modifications. Now, NSM, built on this PR #1571 is  able to work with the DNS grpc target.