chore: address PR comments

Signed-off-by: Jacob Lisi <[email protected]>

Author: jtlisi

pkg/api/handlers.go

@@ -204,7 +204,7 @@ func NewQuerierHandler(
 		InflightRequests: inflightRequests,
 	}
 	cacheGenHeaderMiddleware := getHTTPCacheGenNumberHeaderSetterMiddleware(tombstonesLoader)
-	middlewares := middleware.Merge(fakeRemoteAddr(), inst, cacheGenHeaderMiddleware)
+	middlewares := middleware.Merge(inst, cacheGenHeaderMiddleware)
 	router.Use(middlewares.Wrap)
 
 	promRouter := route.New().WithPrefix(cfg.ServerPrefix + cfg.PrometheusHTTPPrefix + "/api/v1")
@@ -227,9 +227,7 @@ func NewQuerierHandler(
 	// A prefix is fine because external routes will be registered explicitly
 	router.PathPrefix(cfg.LegacyHTTPPrefix + "/api/v1/").Handler(legacyPromRouter)
 
-	// Since we have a new router and the request will not go trough the default server
-	// HTTP middleware stack, we need to add a middleware to extract the trace context
-	// from the HTTP headers and inject it into the Go context.
+	// Add a middleware to extract the trace context and add a header.
 	return nethttp.MiddlewareFunc(opentracing.GlobalTracer(), router.ServeHTTP, nethttp.OperationNameFunc(func(r *http.Request) string {
 		return "internalQuerier"
 	}))

pkg/api/middlewares.go

@@ -10,22 +10,6 @@ import (
 	"github.com/cortexproject/cortex/pkg/querier/queryrange"
 )
 
-// Latest Prometheus requires r.RemoteAddr to be set to addr:port, otherwise it reject the request.
-// Requests to Querier sometimes doesn't have that (if they are fetched from Query-Frontend).
-// Prometheus uses this when logging queries to QueryLogger, but Cortex doesn't call engine.SetQueryLogger to set one.
-//
-// Can be removed when (if) https://github.com/prometheus/prometheus/pull/6840 is merged.
-func fakeRemoteAddr() middleware.Interface {
-	return middleware.Func(func(next http.Handler) http.Handler {
-		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			if r.RemoteAddr == "" {
-				r.RemoteAddr = "127.0.0.1:8888"
-			}
-			next.ServeHTTP(w, r)
-		})
-	})
-}
-
 // middleware for setting cache gen header to let consumer of response know all previous responses could be invalid due to delete operation
 func getHTTPCacheGenNumberHeaderSetterMiddleware(cacheGenNumbersLoader *purger.TombstonesLoader) middleware.Interface {
 	return middleware.Func(func(next http.Handler) http.Handler {

pkg/cortex/modules.go

@@ -206,13 +206,17 @@ func (t *Cortex) initQueryable() (serv services.Service, err error) {
 
 // initQuerier registers an internal HTTP router with a Prometheus API backed by the
 // Cortex Queryable. Then it does one of the following:
+//
 // 1. Query-Frontend Enabled: If Cortex has an All or QueryFrontend target, the internal
 //    HTTP router is wrapped with Tenant ID parsing middleware and passed to the frontend
 //    worker.
+//
 // 2. Querier Standalone: The querier will register the internal HTTP router with the external
 //    HTTP router for the Prometheus API routes. Then the external HTTP server will be passed
 //    as a http.Handler to the frontend worker.
+//
 // Route Diagram:
+//
 //                        │  query
 //                        │ request
 //                        │
@@ -249,6 +253,7 @@ func (t *Cortex) initQueryable() (serv services.Service, err error) {
 //                     └──────────────────────│  Prometheus API  │
 //                                            │                  │
 //                                            └──────────────────┘
+//
 func (t *Cortex) initQuerier() (serv services.Service, err error) {
 	// Create a internal HTTP handler that is configured with the Prometheus API routes and points
 	// to a Prometheus API struct instantiated with the Cortex Queryable.