Add tracing and metrics (prometheus/jaeger/...) capabilities

[zepatrik]

Is your feature request related to a problem? Please describe.

Currently there is no tracing middleware loaded.

Describe the solution you'd like

Instantiation of the servers:

• keto/internal/driver/registry_default.go

  Lines 227 to 239 in 5f25bce

  	func (r *RegistryDefault) ReadGRPCServer() *grpc.Server {
  	s := grpc.NewServer(
  	grpc.StreamInterceptor(
  	grpcMiddleware.ChainStreamServer(
  	grpc_logrus.StreamServerInterceptor(r.l.Entry),
  	),
  	),
  	grpc.UnaryInterceptor(
  	grpcMiddleware.ChainUnaryServer(
  	grpc_logrus.UnaryServerInterceptor(r.l.Entry),
  	),
  	),
  	)

• keto/internal/driver/registry_default.go

  Lines 250 to 262 in 5f25bce

  	func (r *RegistryDefault) WriteGRPCServer() *grpc.Server {
  	s := grpc.NewServer(
  	grpc.StreamInterceptor(
  	grpcMiddleware.ChainStreamServer(
  	grpc_logrus.StreamServerInterceptor(r.l.Entry),
  	),
  	),
  	grpc.UnaryInterceptor(
  	grpcMiddleware.ChainUnaryServer(
  	grpc_logrus.UnaryServerInterceptor(r.l.Entry),
  	),
  	),
  	)

• keto/internal/driver/registry_default.go

  Lines 212 to 213 in 5f25bce

  	func (r *RegistryDefault) WriteRouter() http.Handler {
  	n := negroni.New(reqlog.NewMiddlewareFromLogger(r.l, "write#Ory Keto"))

• keto/internal/driver/registry_default.go

  Lines 197 to 198 in 5f25bce

  	func (r *RegistryDefault) ReadRouter() http.Handler {
  	n := negroni.New(reqlog.NewMiddlewareFromLogger(r.l, "write#Ory Keto"))

Additional context

Kratos' prometheus endpoint implementation: https://github.com/ory/kratos/tree/master/metrics/prometheus
Other tracing options in Kratos can be found here: https://github.com/ory/kratos/blob/412af90a9cc86cb3b2fd8059b6fa51d640b23c05/driver/config/config.go

[aeneasr]

@zepatrik jaeger and prometheus are doing two separate things:

• Jaeger enables tracing - including tracing is very easy, you can check the source code (especially SQL init) from hydra/kratos and just copy paste that
• Prometheus enables metrics - including is also very easy as there are already available metricsx packages in x available (you can also refer to hydra for that!)

Enjoy :)