Feature #630 basic service mesh support for Consul

[evisong]

This PR is trying to implement #630.

Consul ServiceMesh Support

Consul can support ServiceMesh by integrating with proxies like Envoy, the most convenient way to enable this capability is creating a Service like this:

{
 "service": {
   "name": "web",
   "port": 8080,
   "connect": { "sidecar_service": {} }
 }
}

Then Consul will automatically generate a corresponding SidecarService with default configurations.

In Registrator, you may add the "connect": { "sidecar_service": {} } configuration by the -service-mesh flag. It's also overridable by SERVICE_MESH.

Your feedbacks are appreciated.

[vilva42]

@evisong if I understand correctly, -service-mesh and SERVICE_MESH are both representing the same boolean? also is the SERVICE_MESH variable specific to registrator or the container? If it is specific to containers, it would be nice to have a default value of connect": { "sidecar_service": {} } but can be overridden to add upstreams. Most of our containers do not need a sidecar and if they do, they may or may not have upstreams. If there's another way to add upstreams, let us know. Appreciate your work.

[evisong]

if I understand correctly, -service-mesh and SERVICE_MESH are both representing the same boolean? also is the SERVICE_MESH variable specific to registrator or the container? If it is specific to containers, it would be nice to have a default value of connect": { "sidecar_service": {} } but can be overridden to add upstreams. Most of our containers do not need a sidecar and if they do, they may or may not have upstreams. If there's another way to add upstreams, let us know. Appreciate your work.

@vilva42 Sorry for the super-late response. Could you please elaborate on the expected format of upstream configurations? Btw, my dev environment is not available right now, please expect another late response 😢

[vilva42]

hey @evisong Thanks for the response. We decided not to use registrator for this use case.