feat(microservices): add keepalive support for server side

[OlegStrokan]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

No needed to change documentation. I didn't update any interface i just add missing code for
grpc-server implementation (made as gprc-client)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

Currently, when I establish a connection between the gRPC client (running on one laptop) and the gRPC server (running on another laptop) and start a bidirectional stream with keepalive enabled, we can successfully detect a disconnection if I turn off the internet on either machine.
The problem is that the detection happens only on the client side—nothing happens on the server side.
It works if I bypass the keepalive settings and use the bare channelOptions like this:

      channelOptions: {
        'grpc.keepalive_time_ms': 30000,
        'grpc.keepalive_timeout_ms': 5000,
        'grpc.keepalive_permit_without_calls': true,
        'grpc.http2.min_ping_interval_without_data_ms': 25000,
        'grpc.http2.max_pings_without_data': 0,
        'grpc.http2.min_time_between_pings_ms': 10000,
      },

reason: We didn't map this values to keepalive object as we do with gprc-client

And this approach works on the server too, but it’s not a convenient solution for users of the library. It should be consistent with what we have for the gRPC client (when we can use keepalive)

Issue Number: N/A

What is the new behavior?

Successfully detection on both of side after time what we defined in keepalive settings:

  keepalive: {
         keepaliveTimeMs: 30000, 
         keepaliveTimeoutMs: 5000, 
         keepalivePermitWithoutCalls: 1, 
         http2MaxPingsWithoutData: 0, 
         http2MinTimeBetweenPingsMs: 10000, 
         http2MinPingIntervalWithoutDataMs: 25000,
   },

Now we have same approach on client and server side

Does this PR introduce a breaking change?

• Yes
• No

Other information

FYI: I can push repo which have client + server application and provide info about testing with different machines or using containers with iptables

I tested it locally using both a two-machine setup and a multi-container setup. I updated everything locally, built the library, and injected the server files into my project to make the test 100% accurate.

I can provide additional proof if needed.
Thanks

[coveralls]

Pull Request Test Coverage Report for Build d8f120f2-38ca-4d61-af98-39b2ad153111

Details

• 5 of 13 (38.46%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.08%) to 88.858%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/microservices/server/server-grpc.ts	5	13	38.46%

Totals
Change from base Build 378a669f-c115-4f29-a313-f5a0e54f01da:	-0.08%
Covered Lines:	7329
Relevant Lines:	8248

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💛 - Coveralls