[#149] Move middlewares to separate package

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

api/middleware/tracing.go

@@ -0,0 +1,120 @@
+package middleware
+
+import (
+	"context"
+	"net/http"
+	"sync"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
+	"go.opentelemetry.io/otel/attribute"
+	semconv "go.opentelemetry.io/otel/semconv/v1.18.0"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// Tracing adds tracing support for requests.
+// Must be placed after prepareRequest middleware.
+func Tracing() Func {
+	return func(h http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			appCtx, span := StartHTTPServerSpan(r, "REQUEST S3")
+			lw := &traceResponseWriter{ResponseWriter: w, ctx: appCtx, span: span}
+			h.ServeHTTP(lw, r.WithContext(appCtx))
+		})
+	}
+}
+
+type traceResponseWriter struct {
+	sync.Once
+	http.ResponseWriter
+
+	ctx  context.Context
+	span trace.Span
+}
+
+func (lrw *traceResponseWriter) WriteHeader(code int) {
+	lrw.Do(func() {
+		lrw.span.SetAttributes(
+			semconv.HTTPStatusCode(code),
+		)
+
+		carrier := &httpResponseCarrier{resp: lrw.ResponseWriter}
+		tracing.Propagator.Inject(lrw.ctx, carrier)
+
+		lrw.ResponseWriter.WriteHeader(code)
+		lrw.span.End()
+	})
+}
+
+func (lrw *traceResponseWriter) Flush() {
+	if f, ok := lrw.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
+type httpResponseCarrier struct {
+	resp http.ResponseWriter
+}
+
+func (h httpResponseCarrier) Get(key string) string {
+	return h.resp.Header().Get(key)
+}
+
+func (h httpResponseCarrier) Set(key string, value string) {
+	h.resp.Header().Set(key, value)
+}
+
+func (h httpResponseCarrier) Keys() []string {
+	result := make([]string, 0, len(h.resp.Header()))
+	for key := range h.resp.Header() {
+		result = append(result, key)
+	}
+
+	return result
+}
+
+type httpRequestCarrier struct {
+	req *http.Request
+}
+
+func (c *httpRequestCarrier) Get(key string) string {
+	bytes := c.req.Header.Get(key)
+	if len(bytes) == 0 {
+		return ""
+	}
+	return bytes
+}
+
+func (c *httpRequestCarrier) Set(key string, value string) {
+	c.req.Response.Header.Set(key, value)
+}
+
+func (c *httpRequestCarrier) Keys() []string {
+	result := make([]string, 0, len(c.req.Header))
+	for key := range c.req.Header {
+		result = append(result, key)
+	}
+
+	return result
+}
+
+func extractHTTPTraceInfo(ctx context.Context, req *http.Request) context.Context {
+	if req == nil {
+		return ctx
+	}
+	carrier := &httpRequestCarrier{req: req}
+	return tracing.Propagator.Extract(ctx, carrier)
+}
+
+// StartHTTPServerSpan starts root HTTP server span.
+func StartHTTPServerSpan(r *http.Request, operationName string, opts ...trace.SpanStartOption) (context.Context, trace.Span) {
+	ctx := extractHTTPTraceInfo(r.Context(), r)
+	opts = append(opts, trace.WithAttributes(
+		attribute.String("s3.client_address", r.RemoteAddr),
+		attribute.String("s3.path", r.Host),
+		attribute.String("s3.request_id", GetRequestID(r.Context())),
+		semconv.HTTPMethod(r.Method),
+		semconv.RPCService("frostfs-s3-gw"),
+		attribute.String("s3.query", r.RequestURI),
+	), trace.WithSpanKind(trace.SpanKindServer))
+	return tracing.StartSpanFromContext(ctx, operationName, opts...)
+}