ApplyConfig for integrations (#486)

* dynamic metrics endpoint

* add applyconfig

* finish writing code, updating tests

* use common function for converting integration name to key

* no early returns

pkg/integrations/agent/agent.go

@@ -5,9 +5,9 @@ package agent
 
 import (
 	"context"
+	"net/http"
 
 	"github.com/go-kit/kit/log"
-	"github.com/gorilla/mux"
 	"github.com/grafana/agent/pkg/integrations"
 	"github.com/grafana/agent/pkg/integrations/config"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
@@ -48,14 +48,9 @@ func New(c *Config) *Integration {
 	return &Integration{c: c}
 }
 
-// RegisterRoutes satisfies Integration.RegisterRoutes.
-func (i *Integration) RegisterRoutes(r *mux.Router) error {
-	// Note that if the weaveworks common server is set to not register
-	// instrumentation endpoints, this lets the agent integration still be able
-	// to scrape itself, just at /integrations/agent/metrics.
-	r.Handle("/metrics", promhttp.Handler())
-
-	return nil
+// MetricsHandler satisfies Integration.RegisterRoutes.
+func (i *Integration) MetricsHandler() (http.Handler, error) {
+	return promhttp.Handler(), nil
 }
 
 // ScrapeConfigs satisfies Integration.ScrapeConfigs.

pkg/integrations/collector_integration.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"net/http"
 
-	"github.com/gorilla/mux"
 	"github.com/grafana/agent/pkg/integrations/config"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
@@ -61,20 +60,8 @@ func WithExporterMetricsIncluded(included bool) CollectorIntegrationConfig {
 	}
 }
 
-// RegisterRoutes satisfies Integration.RegisterRoutes. The mux.Router provided
-// here is expected to be a subrouter, where all registered paths will be
-// registered within that subroute.
-func (i *CollectorIntegration) RegisterRoutes(r *mux.Router) error {
-	handler, err := i.handler()
-	if err != nil {
-		return err
-	}
-
-	r.Handle("/metrics", handler)
-	return nil
-}
-
-func (i *CollectorIntegration) handler() (http.Handler, error) {
+// MetricsHandler returns the HTTP handler for the integration.
+func (i *CollectorIntegration) MetricsHandler() (http.Handler, error) {
 	r := prometheus.NewRegistry()
 	for _, c := range i.cs {
 		if err := r.Register(c); err != nil {

pkg/integrations/integration.go

@@ -2,9 +2,9 @@ package integrations
 
 import (
 	"context"
+	"net/http"
 
 	"github.com/go-kit/kit/log"
-	"github.com/gorilla/mux"
 	"github.com/grafana/agent/pkg/integrations/config"
 )
 
@@ -25,11 +25,8 @@ type Config interface {
 // An Integration is a process that integrates with some external system and
 // pulls telemetry data.
 type Integration interface {
-	// RegisterRoutes should register any HTTP handlers needed for the
-	// integrations. The mux router provided will be a subrouter for the path
-	// /integrations/<integration name>, where the integration name is retrieved
-	// by the config that created this integration.
-	RegisterRoutes(r *mux.Router) error
+	// MetricsHandler returns an http.Handler that will return metrics.
+	MetricsHandler() (http.Handler, error)
 
 	// ScrapeConfigs returns a set of scrape configs that determine where metrics
 	// can be scraped.