diff --git a/godoc/redirect/redirect.go b/godoc/redirect/redirect.go
index 8208518c180..b4599f6a0fa 100644
--- a/godoc/redirect/redirect.go
+++ b/godoc/redirect/redirect.go
@@ -8,12 +8,18 @@
package redirect // import "golang.org/x/tools/godoc/redirect"
import (
+ "context"
"fmt"
+ "html/template"
"net/http"
"os"
"regexp"
"strconv"
"strings"
+ "sync"
+ "time"
+
+ "golang.org/x/net/context/ctxhttp"
)
// Register registers HTTP handlers that redirect old godoc paths to their new
@@ -193,11 +199,17 @@ func clHandler(w http.ResponseWriter, r *http.Request) {
target := ""
if n, err := strconv.Atoi(id); err == nil && isRietveldCL(n) {
- // TODO: Issue 28836: if this Rietveld CL happens to
+ // Issue 28836: if this Rietveld CL happens to
// also be a Gerrit CL, render a disambiguation HTML
- // page with two links instead. We'll need to make an
- // RPC (to maintner?) to figure that out. For now just
- // redirect to rietveld.
+ // page with two links instead. We need to make a
+ // Gerrit API call to figure that out, but we cache
+ // known Gerrit CLs so it's done at most once per CL.
+ if ok, err := isGerritCL(r.Context(), n); err == nil && ok {
+ w.Header().Set("Content-Type", "text/html; charset=utf-8")
+ clDisambiguationHTML.Execute(w, n)
+ return
+ }
+
target = "https://codereview.appspot.com/" + id
} else {
target = "https://go-review.googlesource.com/" + id
@@ -205,6 +217,64 @@ func clHandler(w http.ResponseWriter, r *http.Request) {
http.Redirect(w, r, target, http.StatusFound)
}
+var clDisambiguationHTML = template.Must(template.New("").Parse(`
+
+
+ Go CL {{.}} Disambiguation
+
+
+
+ CL number {{.}} exists in both Gerrit (the current code review system)
+ and Rietveld (the previous code review system). Please make a choice:
+
+
+
+`))
+
+// isGerritCL reports whether a Gerrit CL with the specified numeric change ID (e.g., "4247")
+// is known to exist by querying the Gerrit API at https://go-review.googlesource.com.
+// isGerritCL uses gerritCLCache as a cache of Gerrit CL IDs that exist.
+func isGerritCL(ctx context.Context, id int) (bool, error) {
+ // Check cache first.
+ gerritCLCache.Lock()
+ ok := gerritCLCache.exist[id]
+ gerritCLCache.Unlock()
+ if ok {
+ return true, nil
+ }
+
+ // Query the Gerrit API Get Change endpoint, as documented at
+ // https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#get-change.
+ ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+ defer cancel()
+ resp, err := ctxhttp.Get(ctx, nil, fmt.Sprintf("https://go-review.googlesource.com/changes/%d", id))
+ if err != nil {
+ return false, err
+ }
+ resp.Body.Close()
+ switch resp.StatusCode {
+ case http.StatusOK:
+ // A Gerrit CL with this ID exists. Add it to cache.
+ gerritCLCache.Lock()
+ gerritCLCache.exist[id] = true
+ gerritCLCache.Unlock()
+ return true, nil
+ case http.StatusNotFound:
+ // A Gerrit CL with this ID doesn't exist. It may get created in the future.
+ return false, nil
+ default:
+ return false, fmt.Errorf("unexpected status code: %v", resp.Status)
+ }
+}
+
+var gerritCLCache = struct {
+ sync.Mutex
+ exist map[int]bool // exist is a set of Gerrit CL IDs that are known to exist.
+}{exist: make(map[int]bool)}
+
var changeMap *hashMap
// LoadChangeMap loads the specified map of Mercurial to Git revisions,