From 94d6b1dd0ffe141b01135218e6e3cfebd5e51eb4 Mon Sep 17 00:00:00 2001
From: Marko <marko@baricevic.me>
Date: Wed, 20 Nov 2024 18:39:09 +0100
Subject: [PATCH] fix(server/v2/api/telemetry): enable global metrics  (#22571)

(cherry picked from commit b45cf753a7a344a275e0489c03360fc91663c220)

# Conflicts:
#	server/v2/api/telemetry/server.go
---
 server/v2/api/telemetry/server.go | 130 ++++++++++++++++++++++++++++++
 simapp/v2/simdv2/cmd/commands.go  |   3 +-
 telemetry/metrics.go              |   5 ++
 3 files changed, 137 insertions(+), 1 deletion(-)
 create mode 100644 server/v2/api/telemetry/server.go

diff --git a/server/v2/api/telemetry/server.go b/server/v2/api/telemetry/server.go
new file mode 100644
index 000000000000..f612964a8476
--- /dev/null
+++ b/server/v2/api/telemetry/server.go
@@ -0,0 +1,130 @@
+package telemetry
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"cosmossdk.io/core/server"
+	"cosmossdk.io/core/transaction"
+	"cosmossdk.io/log"
+	serverv2 "cosmossdk.io/server/v2"
+)
+
+var (
+	_ serverv2.ServerComponent[transaction.Tx] = (*Server[transaction.Tx])(nil)
+	_ serverv2.HasConfig                       = (*Server[transaction.Tx])(nil)
+)
+
+const ServerName = "telemetry"
+
+type Server[T transaction.Tx] struct {
+	logger  log.Logger
+	config  *Config
+	server  *http.Server
+	metrics *Metrics
+}
+
+// New creates a new telemetry server.
+func New[T transaction.Tx](cfg server.ConfigMap, logger log.Logger, enableTelemetry func()) (*Server[T], error) {
+	srv := &Server[T]{}
+	serverCfg := srv.Config().(*Config)
+	if len(cfg) > 0 {
+		if err := serverv2.UnmarshalSubConfig(cfg, srv.Name(), &serverCfg); err != nil {
+			return nil, fmt.Errorf("failed to unmarshal config: %w", err)
+		}
+	}
+	srv.config = serverCfg
+	srv.logger = logger.With(log.ModuleKey, srv.Name())
+
+	if enableTelemetry == nil {
+		panic("enableTelemetry must be provided")
+	}
+
+	if srv.config.Enable {
+		enableTelemetry()
+	}
+
+	metrics, err := NewMetrics(srv.config)
+	if err != nil {
+		return nil, fmt.Errorf("failed to initialize metrics: %w", err)
+	}
+	srv.metrics = metrics
+	return srv, nil
+}
+
+// Name returns the server name.
+func (s *Server[T]) Name() string {
+	return ServerName
+}
+
+func (s *Server[T]) Config() any {
+	if s.config == nil || s.config.Address == "" {
+		return DefaultConfig()
+	}
+
+	return s.config
+}
+
+func (s *Server[T]) Start(ctx context.Context) error {
+	if !s.config.Enable {
+		s.logger.Info(fmt.Sprintf("%s server is disabled via config", s.Name()))
+		return nil
+	}
+
+	mux := http.NewServeMux()
+	// /metrics is the default standard path for Prometheus metrics.
+	mux.HandleFunc("/metrics", s.metricsHandler)
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, "/metrics", http.StatusMovedPermanently)
+	})
+
+	s.server = &http.Server{
+		Addr:    s.config.Address,
+		Handler: mux,
+	}
+
+	s.logger.Info("starting telemetry server...", "address", s.config.Address)
+	if err := s.server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+		return fmt.Errorf("failed to start telemetry server: %w", err)
+	}
+
+	return nil
+}
+
+func (s *Server[T]) Stop(ctx context.Context) error {
+	if !s.config.Enable || s.server == nil {
+		return nil
+	}
+
+	s.logger.Info("stopping telemetry server...", "address", s.config.Address)
+	return s.server.Shutdown(ctx)
+}
+
+func (s *Server[T]) metricsHandler(w http.ResponseWriter, r *http.Request) {
+	format := strings.TrimSpace(r.FormValue("format"))
+
+	// errorResponse defines the attributes of a JSON error response.
+	type errorResponse struct {
+		Code  int    `json:"code,omitempty"`
+		Error string `json:"error"`
+	}
+
+	gr, err := s.metrics.Gather(format)
+	if err != nil {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		bz, err := json.Marshal(errorResponse{Code: 400, Error: fmt.Sprintf("failed to gather metrics: %s", err)})
+		if err != nil {
+			return
+		}
+		_, _ = w.Write(bz)
+
+		return
+	}
+
+	w.Header().Set("Content-Type", gr.ContentType)
+	_, _ = w.Write(gr.Metrics)
+}
diff --git a/simapp/v2/simdv2/cmd/commands.go b/simapp/v2/simdv2/cmd/commands.go
index 24fad3eaa538..9fb41250ec8e 100644
--- a/simapp/v2/simdv2/cmd/commands.go
+++ b/simapp/v2/simdv2/cmd/commands.go
@@ -25,6 +25,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/client/debug"
 	"github.com/cosmos/cosmos-sdk/client/keys"
 	"github.com/cosmos/cosmos-sdk/client/rpc"
+	sdktelemetry "github.com/cosmos/cosmos-sdk/telemetry"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	authcmd "github.com/cosmos/cosmos-sdk/x/auth/client/cli"
 	"github.com/cosmos/cosmos-sdk/x/genutil"
@@ -118,7 +119,7 @@ func InitRootCmd[T transaction.Tx](
 		}
 	}
 
-	telemetryServer, err := telemetry.New[T](deps.GlobalConfig, logger)
+	telemetryServer, err := telemetry.New[T](deps.GlobalConfig, logger, sdktelemetry.EnableTelemetry)
 	if err != nil {
 		return nil, err
 	}
diff --git a/telemetry/metrics.go b/telemetry/metrics.go
index 175261408aae..67ace50c53ec 100644
--- a/telemetry/metrics.go
+++ b/telemetry/metrics.go
@@ -24,6 +24,11 @@ func IsTelemetryEnabled() bool {
 	return globalTelemetryEnabled
 }
 
+// EnableTelemetry allows for the global telemetry enabled state to be set.
+func EnableTelemetry() {
+	globalTelemetryEnabled = true
+}
+
 // globalLabels defines the set of global labels that will be applied to all
 // metrics emitted using the telemetry package function wrappers.
 var globalLabels = []metrics.Label{}