[connector/servicegraph] Update virtual node defaults and change feature gate to beta

[ogxd]

Description:

• Change default values to peer.service, db.name and db.system (in this order). These are compliant with conventions, and the same as the tempo service graph uses.
• Switch the feature from "alpha" to "beta". Virtual nodes are working well on the tempo side, and feature could be disabled anyway by using an empty list if needed.
• Reword documentation for improved clarity
• Fix "processor" that should be "connector" instead since recent commit

Link to tracking Issue: #31734

Testing: No functional change requiring additional tests

Documentation: Updated documentation

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ogxd / name: Olivier Giniaux (31640e0, a977ee5, 69d2ab0, 626046f, 71cb827, 3b376e4, 1ada7e4, b32c07f, 201df8d, 6ff0c07, c2e32c1, b2723fa, ebe3545, 118129d, e3909bb)

[mapno]

This a breaking change, but since the feature was in alpha I think it's still ok to change the attribute list. It now matches the Tempo defaults, so I'm good with the change. Thanks!

[ogxd]

I have rebased + updated the defaults in the feature gate description as well

[JaredTan95]

LGTM

[ogxd]

@jpkrohling can this be merged?

[Frapschen]

@ogxd Sorry for the delay, I think we should add a changelog to notify users

[Frapschen]

feature could be disabled anyway by using an empty list if needed.

I doubt that not work.

opentelemetry-collector-contrib/connector/servicegraphconnector/connector.go

Lines 383 to 394 in 626046f

	if virtualNodeFeatureGate.IsEnabled() {
	e.ConnectionType = store.VirtualNode
	if len(e.ClientService) == 0 && e.Key.SpanIDIsEmpty() {
	e.ClientService = "user"
	p.onComplete(e)
	}
	if len(e.ServerService) == 0 {
	e.ServerService = p.getPeerHost(p.config.VirtualNodePeerAttributes, e.Peer)
	p.onComplete(e)
	}
	}

opentelemetry-collector-contrib/connector/servicegraphconnector/connector.go

Lines 633 to 642 in 626046f

	func (p *serviceGraphConnector) getPeerHost(m []string, peers map[string]string) string {
	peerStr := "unknown"
	for _, s := range m {
	if peer, ok := peers[s]; ok {
	peerStr = peer
	break
	}
	}
	return peerStr
	}

Even when the VirtualNodePeerAttributes is empty, a virtual node service named unknown will exist when this feature gate is enabled by default.

[ogxd]

Indeed, I just added a check to disable the feature if virtual_node_peer_attributes is empty. I also updated the documentation and included a changelog entry.

[Frapschen]

LGTM

[ogxd]

Please excuse me for the bothering 😅
Can this PR be merged? @Frapschen @jpkrohling