internal/frontend: add module and package metadata to codewiki link

- These metrics can provide further granularity for filtering usage
  patterns.

Change-Id: I110854ac2cbcef54d02f1dd02cb27b917ab17705
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/735800
Auto-Submit: Ethan Lee <ethanalee@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
kokoro-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

3 files changed, 21 insertions, 8 deletions

diff --git a/internal/dcensus/dcensus.go b/internal/dcensus/dcensus.go
index 2f6ac7a5..b40b4936 100644
--- a/internal/dcensus/dcensus.go
+++ b/internal/dcensus/dcensus.go
@@ -57,10 +57,12 @@ func NewRouter(tagger RouteTagger) *Router {
 	}
 }
 
-func RecordClick(ctx context.Context, url string, target string) {
+func RecordClick(ctx context.Context, url, target, module, pkg string) {
 	mutators := []tag.Mutator{
 		tag.Upsert(KeyTargetURL, url),
 		tag.Upsert(KeyReferrer, target),
+		tag.Upsert(KeyModule, module),
+		tag.Upsert(KeyPackage, pkg),
 	}
 	stats.RecordWithTags(ctx, mutators, CodeWikiClickCount.M(1))
 }
@@ -254,12 +256,16 @@ var (
 	KeyReferrer = tag.MustNewKey("referrer")
 	// KeyTargetURL is a tag key for the target URL.
 	KeyTargetURL = tag.MustNewKey("target_url")
+	// KeyModule is a tag key for the module path.
+	KeyModule = tag.MustNewKey("module")
+	// KeyPackage is a tag key for the package path.
+	KeyPackage = tag.MustNewKey("package")
 
 	CodeWikiClickCount     = stats.Int64("go-discovery/frontend_codewiki_clicks", "Codewiki link clicks", stats.UnitDimensionless)
 	CodeWikiClickCountView = &view.View{
 		Name:        "go-discovery/frontend/codewiki_clicks",
 		Description: "Count of Codewiki link clicks",
-		TagKeys:     []tag.Key{KeyReferrer, KeyTargetURL},
+		TagKeys:     []tag.Key{KeyReferrer, KeyTargetURL, KeyModule, KeyPackage},
 		Measure:     CodeWikiClickCount,
 		Aggregation: view.Count(),
 	}
diff --git a/internal/frontend/links.go b/internal/frontend/links.go
index 3e8a4de4..e4ecb701 100644
--- a/internal/frontend/links.go
+++ b/internal/frontend/links.go
@@ -24,7 +24,7 @@ const (
 	// depsDevTimeout is the time budget for making requests to deps.dev.
 	depsDevTimeout = 250 * time.Millisecond
 
-	codeWikiPrefix    = "/codewiki?url="
+	codeWikiPrefix    = "/codewiki?"
 	attributionParams = "?utm_source=first_party_link&utm_medium=go_pkg_web&utm_campaign="
 )
 
@@ -111,14 +111,15 @@ func fetchDepsDevURL(ctx context.Context, client *http.Client, modulePath, versi
 // codeWikiTimeout then the empty string is returned instead.
 func codeWikiURLGenerator(ctx context.Context, client *http.Client, um *internal.UnitMeta, recordClick bool) func() string {
 	fetch := func(ctx context.Context, client *http.Client) (string, error) {
-		return fetchCodeWikiURL(ctx, client, um.ModulePath, recordClick)
+		return fetchCodeWikiURL(ctx, client, um, recordClick)
 	}
 	return newURLGenerator(ctx, client, "codewiki.google", codeWikiTimeout, fetch)
 }
 
 // fetchCodeWikiURL makes a request to codewiki to check whether the given
 // path is known there, and if so it returns the link to that page.
-func fetchCodeWikiURL(ctx context.Context, client *http.Client, path string, recordClick bool) (string, error) {
+func fetchCodeWikiURL(ctx context.Context, client *http.Client, um *internal.UnitMeta, recordClick bool) (string, error) {
+	path := um.ModulePath
 	if strings.HasPrefix(path, "golang.org/x/") {
 		path = strings.Replace(path, "golang.org/x/", "github.com/golang/", 1)
 	}
@@ -144,7 +145,11 @@ func fetchCodeWikiURL(ctx context.Context, client *http.Client, path string, rec
 	}
 	res := codeWikiURLBase + path + attributionParams + path
 	if recordClick {
-		res = codeWikiPrefix + url.QueryEscape(res)
+		v := url.Values{}
+		v.Set("url", res)
+		v.Set("module", um.ModulePath)
+		v.Set("package", um.Path)
+		res = codeWikiPrefix + v.Encode()
 	}
 	return res, nil
 }
diff --git a/internal/frontend/server.go b/internal/frontend/server.go
index 9648c5e7..5a554635 100644
--- a/internal/frontend/server.go
+++ b/internal/frontend/server.go
@@ -78,7 +78,7 @@ type FetchServerInterface interface {
 		ds internal.PostgresDB, fullPath, modulePath, requestedVersion string) (err error)
 }
 
-type RecordClickFunc func(ctx context.Context, url string, target string)
+type RecordClickFunc func(ctx context.Context, url, target, module, pkg string)
 
 // ServerConfig contains everything needed by a Server.
 type ServerConfig struct {
@@ -148,13 +148,15 @@ func NewServer(scfg ServerConfig) (_ *Server, err error) {
 
 func (s *Server) handleCodeWikiRedirect(w http.ResponseWriter, r *http.Request) {
 	url := r.FormValue("url")
+	module := r.FormValue("module")
+	pkg := r.FormValue("package")
 	if url == "" {
 		http.Error(w, "missing url", http.StatusBadRequest)
 		return
 	}
 	ctx := r.Context()
 	if s.recordCodeWikiMetrics != nil {
-		s.recordCodeWikiMetrics(ctx, url, r.Header.Get("Referer"))
+		s.recordCodeWikiMetrics(ctx, url, r.Header.Get("Referer"), module, pkg)
 	}
 	http.Redirect(w, r, url, http.StatusFound)
 }