internal/middleware: move stats to its own package

Make a package internal/middleware/stats for middleware.Stats and
middleware.ElapsedStat. This is part of removing the dependency from
internal/frontend on internal/middleware.

For golang/go#61399

Change-Id: I44afbfc9b9e28e1caabab8fe700376ec026c863d
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/514521
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Michael Matloob <[email protected]>
Reviewed-by: Jamal Carvalho <[email protected]>
kokoro-CI: kokoro <[email protected]>

Author: matloob

internal/frontend/details.go

@@ -7,6 +7,7 @@ package frontend
 import (
 	"context"
 	"errors"
+	mstats "golang.org/x/pkgsite/internal/middleware/stats"
 	"net/http"
 	"strings"
 
@@ -16,7 +17,6 @@ import (
 	"go.opencensus.io/tag"
 	"golang.org/x/mod/semver"
 	"golang.org/x/pkgsite/internal"
-	"golang.org/x/pkgsite/internal/middleware"
 	"golang.org/x/pkgsite/internal/stdlib"
 )
 
@@ -25,7 +25,7 @@ import (
 // stdlib module pages are handled at "/std", and requests to "/mod/std" will
 // be redirected to that path.
 func (s *Server) serveDetails(w http.ResponseWriter, r *http.Request, ds internal.DataSource) (err error) {
-	defer middleware.ElapsedStat(r.Context(), "serveDetails")()
+	defer mstats.Elapsed(r.Context(), "serveDetails")()
 
 	ctx := r.Context()
 	if r.Method != http.MethodGet && r.Method != http.MethodHead {

internal/frontend/doc.go

@@ -16,14 +16,14 @@ import (
 	"golang.org/x/pkgsite/internal/godoc"
 	"golang.org/x/pkgsite/internal/godoc/dochtml"
 	"golang.org/x/pkgsite/internal/log"
-	"golang.org/x/pkgsite/internal/middleware"
+	"golang.org/x/pkgsite/internal/middleware/stats"
 	"golang.org/x/pkgsite/internal/stdlib"
 )
 
 func renderDocParts(ctx context.Context, u *internal.Unit, docPkg *godoc.Package,
 	nameToVersion map[string]string, bc internal.BuildContext) (_ *dochtml.Parts, err error) {
 	defer derrors.Wrap(&err, "renderDocParts")
-	defer middleware.ElapsedStat(ctx, "renderDocParts")()
+	defer stats.Elapsed(ctx, "renderDocParts")()
 
 	modInfo := &godoc.ModuleInfo{
 		ModulePath:      u.ModulePath,

internal/frontend/latest_version.go

@@ -9,7 +9,7 @@ import (
 
 	"golang.org/x/pkgsite/internal"
 	"golang.org/x/pkgsite/internal/log"
-	"golang.org/x/pkgsite/internal/middleware"
+	"golang.org/x/pkgsite/internal/middleware/stats"
 )
 
 // GetLatestInfo returns various pieces of information about the latest
@@ -21,7 +21,7 @@ import (
 // It returns empty strings on error.
 // It is intended to be used as an argument to middleware.LatestVersions.
 func (s *Server) GetLatestInfo(ctx context.Context, unitPath, modulePath string, latestUnitMeta *internal.UnitMeta) internal.LatestInfo {
-	defer middleware.ElapsedStat(ctx, "GetLatestInfo")()
+	defer stats.Elapsed(ctx, "GetLatestInfo")()
 
 	// It is okay to use a different DataSource (DB connection) than the rest of the
 	// request, because this makes self-contained calls on the DB.

internal/frontend/main.go

@@ -17,6 +17,7 @@ import (
 	"golang.org/x/pkgsite/internal/godoc/dochtml"
 	"golang.org/x/pkgsite/internal/log"
 	"golang.org/x/pkgsite/internal/middleware"
+	"golang.org/x/pkgsite/internal/middleware/stats"
 	"golang.org/x/pkgsite/internal/version"
 	"golang.org/x/text/message"
 )
@@ -107,7 +108,7 @@ type File struct {
 
 func fetchMainDetails(ctx context.Context, ds internal.DataSource, um *internal.UnitMeta,
 	requestedVersion string, expandReadme bool, bc internal.BuildContext) (_ *MainDetails, err error) {
-	defer middleware.ElapsedStat(ctx, "fetchMainDetails")()
+	defer stats.Elapsed(ctx, "fetchMainDetails")()
 
 	unit, err := ds.GetUnit(ctx, um, internal.WithMain, bc)
 	if err != nil {
@@ -146,7 +147,7 @@ func fetchMainDetails(ctx context.Context, ds internal.DataSource, um *internal.
 		goos = doc.GOOS
 		goarch = doc.GOARCH
 		buildContexts = unit.BuildContexts
-		end := middleware.ElapsedStat(ctx, "DecodePackage")
+		end := stats.Elapsed(ctx, "DecodePackage")
 		docPkg, err := godoc.DecodePackage(doc.Source)
 		end()
 		if err != nil {
@@ -167,7 +168,7 @@ func fetchMainDetails(ctx context.Context, ds internal.DataSource, um *internal.
 		for _, l := range docParts.Links {
 			docLinks = append(docLinks, link{Href: l.Href, Body: l.Text})
 		}
-		end = middleware.ElapsedStat(ctx, "sourceFiles")
+		end = stats.Elapsed(ctx, "sourceFiles")
 		files = sourceFiles(unit, docPkg)
 		end()
 	}
@@ -253,7 +254,7 @@ func cleanDocumentation(docs []*internal.Documentation) []*internal.Documentatio
 // into an outline.
 func readmeContent(ctx context.Context, u *internal.Unit) (_ *Readme, err error) {
 	defer derrors.Wrap(&err, "readmeContent(%q, %q, %q)", u.Path, u.ModulePath, u.Version)
-	defer middleware.ElapsedStat(ctx, "readmeContent")()
+	defer stats.Elapsed(ctx, "readmeContent")()
 	if !u.IsRedistributable {
 		return &Readme{}, nil
 	}

internal/frontend/server.go

@@ -32,7 +32,7 @@ import (
 	"golang.org/x/pkgsite/internal/licenses"
 	"golang.org/x/pkgsite/internal/log"
 	"golang.org/x/pkgsite/internal/memory"
-	"golang.org/x/pkgsite/internal/middleware"
+	"golang.org/x/pkgsite/internal/middleware/stats"
 	"golang.org/x/pkgsite/internal/queue"
 	"golang.org/x/pkgsite/internal/static"
 	"golang.org/x/pkgsite/internal/version"
@@ -198,9 +198,9 @@ func (s *Server) Install(handle func(string, http.Handler), cacher Cacher, authV
 	handle("/", detailHandler)
 	if s.serveStats {
 		handle("/detail-stats/",
-			middleware.Stats()(http.StripPrefix("/detail-stats", s.errorHandler(s.serveDetails))))
+			stats.Stats()(http.StripPrefix("/detail-stats", s.errorHandler(s.serveDetails))))
 		handle("/search-stats/",
-			middleware.Stats()(http.StripPrefix("/search-stats", s.errorHandler(s.serveSearch))))
+			stats.Stats()(http.StripPrefix("/search-stats", s.errorHandler(s.serveSearch))))
 	}
 	handle("/robots.txt", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
@@ -672,7 +672,7 @@ func (s *Server) renderErrorPage(ctx context.Context, status int, templateName s
 
 // servePage is used to execute all templates for a *Server.
 func (s *Server) servePage(ctx context.Context, w http.ResponseWriter, templateName string, page any) {
-	defer middleware.ElapsedStat(ctx, "servePage")()
+	defer stats.Elapsed(ctx, "servePage")()
 
 	buf, err := s.renderPage(ctx, templateName, page)
 	if err != nil {
@@ -688,7 +688,7 @@ func (s *Server) servePage(ctx context.Context, w http.ResponseWriter, templateN
 
 // renderPage executes the given templateName with page.
 func (s *Server) renderPage(ctx context.Context, templateName string, page any) ([]byte, error) {
-	defer middleware.ElapsedStat(ctx, "renderPage")()
+	defer stats.Elapsed(ctx, "renderPage")()
 
 	tmpl, err := s.findTemplate(templateName)
 	if err != nil {

internal/frontend/unit.go

@@ -18,7 +18,7 @@ import (
 	"golang.org/x/pkgsite/internal/cookie"
 	"golang.org/x/pkgsite/internal/derrors"
 	"golang.org/x/pkgsite/internal/log"
-	"golang.org/x/pkgsite/internal/middleware"
+	"golang.org/x/pkgsite/internal/middleware/stats"
 	"golang.org/x/pkgsite/internal/stdlib"
 	"golang.org/x/pkgsite/internal/version"
 	"golang.org/x/pkgsite/internal/vuln"
@@ -106,7 +106,7 @@ type UnitPage struct {
 func (s *Server) serveUnitPage(ctx context.Context, w http.ResponseWriter, r *http.Request,
 	ds internal.DataSource, info *urlPathInfo) (err error) {
 	defer derrors.Wrap(&err, "serveUnitPage(ctx, w, r, ds, %v)", info)
-	defer middleware.ElapsedStat(ctx, "serveUnitPage")()
+	defer stats.Elapsed(ctx, "serveUnitPage")()
 
 	tab := r.FormValue("tab")
 	if tab == "" {

internal/middleware/stats.go renamed to internal/middleware/stats/stats.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package middleware
+package stats
 
 import (
 	"context"
@@ -18,7 +18,7 @@ type statsKey struct{}
 
 // Stats returns a Middleware that, instead of serving the page,
 // serves statistics about the page.
-func Stats() Middleware {
+func Stats() func(http.Handler) http.Handler {
 	return func(h http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			sw := newStatsResponseWriter()
@@ -29,9 +29,9 @@ func Stats() Middleware {
 	}
 }
 
-// SetStat sets a stat named key in the current context. If key already has a
+// set sets a stat named key in the current context. If key already has a
 // value, the old and new value are both stored in a slice.
-func SetStat(ctx context.Context, key string, value any) {
+func set(ctx context.Context, key string, value any) {
 	x := ctx.Value(statsKey{})
 	if x == nil {
 		return
@@ -47,17 +47,17 @@ func SetStat(ctx context.Context, key string, value any) {
 	}
 }
 
-// ElapsedStat records as a stat the elapsed time for a
+// Elapsed records as a stat the elapsed time for a
 // function execution. Invoke like so:
 //
-//	defer ElapsedStat(ctx, "FunctionName")()
+//	defer Elapsed(ctx, "FunctionName")()
 //
 // The resulting stat will be called "FunctionName ms" and will
 // be the wall-clock execution time of the function in milliseconds.
-func ElapsedStat(ctx context.Context, name string) func() {
+func Elapsed(ctx context.Context, name string) func() {
 	start := time.Now()
 	return func() {
-		SetStat(ctx, name+" ms", time.Since(start).Milliseconds())
+		set(ctx, name+" ms", time.Since(start).Milliseconds())
 	}
 }
 

internal/middleware/stats_test.go renamed to internal/middleware/stats/stats_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package middleware
+package stats
 
 import (
 	"encoding/json"
@@ -23,11 +23,11 @@ func TestStats(t *testing.T) {
 	ts := httptest.NewServer(Stats()(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		ctx := r.Context()
 		w.WriteHeader(code)
-		SetStat(ctx, "a", 1)
+		set(ctx, "a", 1)
 		w.Write(data[:10])
-		SetStat(ctx, "b", 2)
+		set(ctx, "b", 2)
 		time.Sleep(500 * time.Millisecond)
-		SetStat(ctx, "a", 3)
+		set(ctx, "a", 3)
 		w.Write(data[10:])
 	})))
 	defer ts.Close()

internal/postgres/details.go

@@ -15,14 +15,14 @@ import (
 	"golang.org/x/pkgsite/internal"
 	"golang.org/x/pkgsite/internal/database"
 	"golang.org/x/pkgsite/internal/derrors"
-	"golang.org/x/pkgsite/internal/middleware"
+	"golang.org/x/pkgsite/internal/middleware/stats"
 )
 
 // GetNestedModules returns the latest major version of all nested modules
 // given a modulePath path prefix with or without major version.
 func (db *DB) GetNestedModules(ctx context.Context, modulePath string) (_ []*internal.ModuleInfo, err error) {
 	defer derrors.WrapStack(&err, "GetNestedModules(ctx, %v)", modulePath)
-	defer middleware.ElapsedStat(ctx, "GetNestedModules")()
+	defer stats.Elapsed(ctx, "GetNestedModules")()
 
 	query := `
 		SELECT DISTINCT ON (series_path)
@@ -78,7 +78,7 @@ func (db *DB) GetNestedModules(ctx context.Context, modulePath string) (_ []*int
 // Instead of supporting pagination, this query runs with a limit.
 func (db *DB) GetImportedBy(ctx context.Context, pkgPath, modulePath string, limit int) (paths []string, err error) {
 	defer derrors.WrapStack(&err, "GetImportedBy(ctx, %q, %q)", pkgPath, modulePath)
-	defer middleware.ElapsedStat(ctx, "GetImportedBy")()
+	defer stats.Elapsed(ctx, "GetImportedBy")()
 
 	if pkgPath == "" {
 		return nil, fmt.Errorf("pkgPath cannot be empty: %w", derrors.InvalidArgument)
@@ -102,7 +102,7 @@ func (db *DB) GetImportedBy(ctx context.Context, pkgPath, modulePath string, lim
 // GetImportedByCount returns the number of packages that import pkgPath.
 func (db *DB) GetImportedByCount(ctx context.Context, pkgPath, modulePath string) (_ int, err error) {
 	defer derrors.WrapStack(&err, "GetImportedByCount(ctx, %q, %q)", pkgPath, modulePath)
-	defer middleware.ElapsedStat(ctx, "GetImportedByCount")()
+	defer stats.Elapsed(ctx, "GetImportedByCount")()
 
 	if pkgPath == "" {
 		return 0, fmt.Errorf("pkgPath cannot be empty: %w", derrors.InvalidArgument)

internal/postgres/licenses.go

@@ -17,13 +17,13 @@ import (
 	"github.com/lib/pq"
 	"golang.org/x/pkgsite/internal/derrors"
 	"golang.org/x/pkgsite/internal/licenses"
-	"golang.org/x/pkgsite/internal/middleware"
+	"golang.org/x/pkgsite/internal/middleware/stats"
 	"golang.org/x/pkgsite/internal/stdlib"
 )
 
 func (db *DB) getLicenses(ctx context.Context, fullPath, modulePath string, unitID int) (_ []*licenses.License, err error) {
 	defer derrors.WrapStack(&err, "getLicenses(ctx, %d)", unitID)
-	defer middleware.ElapsedStat(ctx, "getLicenses")()
+	defer stats.Elapsed(ctx, "getLicenses")()
 
 	query := `
 		SELECT