[Multi-cluster] Some pages are broken when meshID is not set

[nrfox]

When the meshID is not set, the istio api does not populate the clusters field on the /config response. The frontend looks for this clusters field to determine whether or not Kiali is in "multi-cluster mode".

[jshaughn]

if meshID is not set does it have some default value or is it simply unset? IIrc it's just unset and so clusters would not be returned and I think Istio is assuming a single cluster, and I guess we should as well?

[nrfox]

if meshID is not set does it have some default value or is it simply unset?

At least in the env I tested in and where Kiali is reading this in the default config, it is unset.

kiali/business/mesh.go

Lines 173 to 181 in ecd24d3

	meshConfig := meshIdConfig{}
	err = yaml.Unmarshal([]byte(meshConfigYaml), &meshConfig)
	if err != nil {
	return false, err
	}
	if len(meshConfig.DefaultConfig.MeshId) > 0 {
	isMeshConfigured = true
	}

Yeah I think the clusters field was populated based on "best effort" but for better or worse some parts of Kiali use that field like if clusters > 1: do MC things else do single cluster things. This is used on the frontend to hide the cluster column for example and I think it's used on the backend too. When the clusters field is empty or == 1 then kiali assumes singlecluster. The cache, on the other hand, does not look at this clusters field and correctly starts talking to the remote clusters when there's a remote secret added.

[jmazzitelli]

Right - that MeshID istio config is the key to turning on the Mesh page/left-hand-menu item.

[jshaughn]

This is a little confusing, is meshID required for Istio itself to be MC? If so then it seems that we should honor what it tells us in /config. It would be a little strange that Kiali would assume MC, based on secrets, when Istio itself doesn't think it's MC.

[nrfox]

This is a little confusing, is meshID required for Istio itself to be MC? If so then it seems that we should honor what it tells us in /config. It would be a little strange that Kiali would assume MC, based on secrets, when Istio itself doesn't think it's MC.

I think it's only required if you have multiple meshes and want to distinguish between them. It also may be emitted by telemetry for these purposes. In other words, I don't think setting the meshID enables MC in istio.

[jshaughn]

I think meshID may actually be injected into the telemetry for cross-mesh traffic (I think there is a default value related to the trust domain), although Kiali does not handle cross-mesh at this time.

Anyway, it sounds like we need to trust our secrets and report the clusters that way.