xds: v3 support: client bootstrap

[easwars]

This PR adds support in the client bootstrap code to support xDS v3 API.

• Server support for v3 is indicated in the bootstrap file by a new field server_features.
• On the client side, v3 API is enabled when the GRPC_XDS_EXPERIMENTAL_V3_SUPPORT environment variable is set to true.

Rest of the client side v3 support will be added in follow up PRs.

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This change is 

[easwars]

I don't understand the travis test failures. I have locally been able to run the tests with -race and -count=1000 and they pass all the time.

[menghanl]

Reviewed 8 of 9 files at r1.
Reviewable status: 8 of 9 files reviewed, 5 unresolved discussions (waiting on @easwars and @menghanl)

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xds/internal/client/client.go, line 137 at r1 (raw file):

	if opts.Config.TransportAPI == version.TransportV2 {
		c.v2c = newXDSV2Client(c, cc, opts.Config.NodeProto.(*corepb.Node), backoff.DefaultExponential.Backoff, c.logger)
	}

else? Return error? Or this will cause nil panic?

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xds/internal/client/bootstrap/bootstrap.go, line 145 at r1 (raw file):

			// does not contain the deprecated field "build_version" from the
			// v2.Node proto. We expect this to succeed because we do not expect
			// the bootstrap file to contain the "build_version" field.

Even if it does, unmarshal won't fail, because of AllowUnknownFields

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xds/internal/client/bootstrap/bootstrap.go, line 226 at r1 (raw file):

Quoted 4 lines of code…

		v3 := &v3corepb.Node{}
		if c.NodeProto != nil {
			v3 = c.NodeProto.(*v3corepb.Node)
		}

Does this save an allocation?

v3, _ := c.NodeProto.(*v3corepb.Node)
if v3 == nil {
  v3 = &v3corepb.Node{}
}

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xds/internal/client/bootstrap/bootstrap.go, line 249 at r1 (raw file):

	// user_agent_version. But the management servers are still using the old
	// field, so we will keep both set.
	// API version for xDS transport protocol. This describes the xDS gRPC/REST

Is this comment right?

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xds/internal/version/version.go, line 20 at r1 (raw file):

// Package version defines supported xDS API versions.
package version

Move to client/?
This is only used by clients, not by the balancers/resolvers, right?

[menghanl]

Travis failure could be googleapis/google-cloud-go#2417
Fixed by their 0.59.0 release (though there's a newer 0.60.0)

But we don't explicitly depend on them. Try to update golang.org/x/oauth2 maybe

[easwars]

Reviewable status: 8 of 9 files reviewed, 5 unresolved discussions (waiting on @menghanl)

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xds/internal/client/client.go, line 137 at r1 (raw file):

Previously, menghanl (Menghan Li) wrote…

else? Return error? Or this will cause nil panic?

Done.

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xds/internal/client/bootstrap/bootstrap.go, line 145 at r1 (raw file):

Previously, menghanl (Menghan Li) wrote…

Even if it does, unmarshal won't fail, because of AllowUnknownFields

Updated the comment.

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xds/internal/client/bootstrap/bootstrap.go, line 226 at r1 (raw file):

Previously, menghanl (Menghan Li) wrote…

		v3 := &v3corepb.Node{}
		if c.NodeProto != nil {
			v3 = c.NodeProto.(*v3corepb.Node)
		}

Does this save an allocation?

v3, _ := c.NodeProto.(*v3corepb.Node)
if v3 == nil {
  v3 = &v3corepb.Node{}
}

Done. Thanks.

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xds/internal/client/bootstrap/bootstrap.go, line 249 at r1 (raw file):

Previously, menghanl (Menghan Li) wrote…

Is this comment right?

The comment by itself is correct :), but I don't remember why I put it here. Removed it.

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xds/internal/version/version.go, line 20 at r1 (raw file):

Previously, menghanl (Menghan Li) wrote…

Move to client/?
This is only used by clients, not by the balancers/resolvers, right?

Will probably be used on the server side as well.

[easwars]

Travis failure could be googleapis/google-cloud-go#2417
Fixed by their 0.59.0 release (though there's a newer 0.60.0)

But we don't explicitly depend on them. Try to update golang.org/x/oauth2 maybe

Updating didn't help. Although that issue is marked as closed, it does look like the problem is not completely fixed. I reverted the change to enable the leak check. Let's see if travis becomes happy.

[menghanl]

Try to explicitly ping cloud libraries to 0.60.0?
If the leak still happens, we should ping the issue.

[easwars]

Travis is happy.

[menghanl]

Reviewed 1 of 9 files at r1, 3 of 5 files at r2, 1 of 2 files at r3.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @easwars)

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go.sum, line 69 at r3 (raw file):

honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc h1:/hemPrYIhOhy8zYrNj+069zDB68us2sMGsfkFJO0iZs=
honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

Revert?