Exposed runtime metrics (#10)

- Key changes:
  - Exposed runtime metrics.

CHANGELOG.md

@@ -1,5 +1,10 @@
 # CHANGELOG
 
+## 0.8.0
+
+- Key changes:
+  - Exposed runtime metrics.
+
 ## 0.7.0
 
 - Key changes:

cmd/lfgw/acl.go

@@ -94,6 +94,7 @@ func (a *ACL) PrepareLF(ns string) (metricsql.LabelFilter, error) {
 	return lf, nil
 }
 
+// loadACL loads ACL from a file
 func (app *application) loadACL() (ACLMap, error) {
 	aclMap := make(ACLMap)
 
@@ -176,7 +177,7 @@ func (app *application) getLF(roles []string) (metricsql.LabelFilter, error) {
 		return app.ACLMap[role].LabelFilter, nil
 	}
 
-	// If a user has a fullaccess role, there's no need to check any other one
+	// If a user has a fullaccess role, there's no need to check any other one.
 	for _, role := range roles {
 		if app.ACLMap[role].Fullaccess {
 			return app.ACLMap[role].LabelFilter, nil

cmd/lfgw/helpers.go

@@ -47,7 +47,7 @@ func (app *application) getRawAccessToken(r *http.Request) (string, error) {
 	return "", fmt.Errorf("no bearer token found")
 }
 
-// lshortfile implements Lshortfile equivalent for zerolog's CallerMarshalFunc
+// lshortfile implements Lshortfile equivalent for zerolog's CallerMarshalFunc.
 func (app *application) lshortfile(file string, line int) string {
 	// Copied from the standard library: https://cs.opensource.google/go/go/+/refs/tags/go1.17.8:src/log/log.go;drc=926994fd7cf65b2703552686965fb05569699897;l=134
 	short := file
@@ -61,7 +61,7 @@ func (app *application) lshortfile(file string, line int) string {
 	return file + ":" + strconv.Itoa(line)
 }
 
-// enrichLogContext adds a custom field and a value to zerolog context
+// enrichLogContext adds a custom field and a value to zerolog context.
 func (app *application) enrichLogContext(r *http.Request, field string, value string) {
 	if field != "" && value != "" {
 		log := zerolog.Ctx(r.Context())
@@ -71,7 +71,7 @@ func (app *application) enrichLogContext(r *http.Request, field string, value st
 	}
 }
 
-// enrichDebugLogContext adds a custom field and a value to zerolog context if logging level is set to Debug
+// enrichDebugLogContext adds a custom field and a value to zerolog context if logging level is set to Debug.
 func (app *application) enrichDebugLogContext(r *http.Request, field string, value string) {
 	if app.Debug {
 		if field != "" && value != "" {
@@ -83,10 +83,12 @@ func (app *application) enrichDebugLogContext(r *http.Request, field string, val
 	}
 }
 
+// isNotAPIRequest returns true if the requested path does not target API or federate endpoints.
 func (app *application) isNotAPIRequest(path string) bool {
 	return !strings.Contains(path, "/api/") && !strings.Contains(path, "/federate")
 }
 
+// isUnsafePath returns true if the requested path targets a potentially dangerous endpoint (admin or remote write).
 func (app *application) isUnsafePath(path string) bool {
 	// TODO: move to regexp?
 	return strings.Contains(path, "/admin/tsdb") || strings.Contains(path, "/api/v1/write")

cmd/lfgw/lf.go

@@ -90,7 +90,7 @@ func (app *application) optimizeMetricExpr(expr metricsql.Expr) metricsql.Expr {
 	return newExpr
 }
 
-// equalExpr says whether two expressions are equal
+// equalExpr says whether two expressions are equal.
 func (app *application) equalExpr(expr1 metricsql.Expr, expr2 metricsql.Expr) bool {
 	return string(expr1.AppendString(nil)) == string(expr2.AppendString(nil))
 }

cmd/lfgw/logwrapper.go

@@ -12,6 +12,7 @@ type stdErrorLogWrapper struct {
 
 // TODO: new?
 
+// Write implements io.Writer interface to redirect standard logger entries to zerolog. Also, it cuts caller from a log entry and passes it to zerolog's caller.
 func (s stdErrorLogWrapper) Write(p []byte) (n int, err error) {
 	caller, errorMsg, _ := strings.Cut(string(p), " ")
 	caller = strings.TrimRight(caller, ":")

cmd/lfgw/middleware.go

@@ -8,22 +8,30 @@ import (
 	"strings"
 	"time"
 
+	"github.com/VictoriaMetrics/metrics"
 	"github.com/VictoriaMetrics/metricsql"
 	"github.com/rs/zerolog/hlog"
 )
 
-// healthzMiddleware is a workaround to support healthz endpoint while forwarding everything else to an upstream.
-func (app *application) healthzMiddleware(next http.Handler) http.Handler {
+// nonProxiedEndpointsMiddleware is a workaround to support healthz and metrics endpoints while forwarding everything else to an upstream.
+func (app *application) nonProxiedEndpointsMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if strings.HasPrefix(r.URL.Path, "/healthz") {
 			w.WriteHeader(http.StatusOK)
 			return
 		}
+
+		if strings.HasPrefix(r.URL.Path, "/metrics") {
+			metrics.WritePrometheus(w, true)
+			return
+		}
+
 		next.ServeHTTP(w, r)
 	})
 }
 
-func (app *application) logHandler(next http.Handler) http.Handler {
+// logMiddleware populates zerolog context with additional fields that are used in log entries generated by other middlewares. Also, it optionally generates access logs.
+func (app *application) logMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		next = hlog.RequestIDHandler("req_id", "Request-Id")(next)
 

cmd/lfgw/routes.go

@@ -8,9 +8,9 @@ import (
 // routes returns a router with all paths.
 func (app *application) routes() *mux.Router {
 	r := mux.NewRouter()
-	r.Use(app.healthzMiddleware)
+	r.Use(app.nonProxiedEndpointsMiddleware)
 	r.Use(hlog.NewHandler(*app.logger))
-	r.Use(app.logHandler)
+	r.Use(app.logMiddleware)
 	r.Use(app.prohibitedMethodsMiddleware)
 	r.Use(app.proxyHeadersMiddleware)
 	r.Use(app.oidcModeMiddleware)

go.mod

@@ -3,6 +3,7 @@ module gitlab.rshbdev.ru/rshbintech/integrations/ckpr/infra/images/lfgw
 go 1.18
 
 require (
+	github.com/VictoriaMetrics/metrics v1.18.1
 	github.com/VictoriaMetrics/metricsql v0.40.0
 	github.com/caarlos0/env/v6 v6.9.1
 	github.com/coreos/go-oidc/v3 v3.1.0
@@ -12,7 +13,6 @@ require (
 )
 
 require (
-	github.com/VictoriaMetrics/metrics v1.18.1 // indirect
 	github.com/golang/protobuf v1.4.3 // indirect
 	github.com/rs/xid v1.3.0 // indirect
 	github.com/valyala/fastrand v1.1.0 // indirect