Merge pull request #3143 from eyJhb/pagination

OCI: Add pagination on `/v2/<name>/tags/list`

registry/api/v2/descriptors.go

@@ -490,6 +490,18 @@ var routeDescriptors = []RouteDescriptor{
 							},
 						},
 						Failures: []ResponseDescriptor{
+							{
+								Name:        "Invalid pagination number",
+								Description: "The received parameter n was invalid in some way, as described by the error code. The client should resolve the issue and retry the request.",
+								StatusCode:  http.StatusBadRequest,
+								Body: BodyDescriptor{
+									ContentType: "application/json",
+									Format:      errorsBody,
+								},
+								ErrorCodes: []errcode.ErrorCode{
+									ErrorCodePaginationNumberInvalid,
+								},
+							},
 							unauthorizedResponseDescriptor,
 							repositoryNotFoundResponseDescriptor,
 							deniedResponseDescriptor,

registry/api/v2/errors.go

@@ -144,4 +144,14 @@ var (
 		longer proceed.`,
 		HTTPStatusCode: http.StatusNotFound,
 	})
+
+	// ErrorCodePaginationNumberInvalid is returned when the `n` parameter is
+	// not an integer, or `n` is negative.
+	ErrorCodePaginationNumberInvalid = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "PAGINATION_NUMBER_INVALID",
+		Message: "invalid number of results requested",
+		Description: `Returned when the "n" parameter (number of results
+		to return) is not an integer, or "n" is negative.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})
 )

registry/handlers/tags.go

@@ -3,6 +3,8 @@ package handlers
 import (
 	"encoding/json"
 	"net/http"
+	"sort"
+	"strconv"
 
 	"github.com/distribution/distribution/v3"
 	"github.com/distribution/distribution/v3/registry/api/errcode"
@@ -49,6 +51,51 @@ func (th *tagsHandler) GetTags(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// do pagination if requested
+	q := r.URL.Query()
+	// get entries after latest, if any specified
+	if lastEntry := q.Get("last"); lastEntry != "" {
+		lastEntryIndex := sort.SearchStrings(tags, lastEntry)
+
+		// as`sort.SearchStrings` can return len(tags), if the
+		// specified `lastEntry` is not found, we need to
+		// ensure it does not panic when slicing.
+		if lastEntryIndex == len(tags) {
+			tags = []string{}
+		} else {
+			tags = tags[lastEntryIndex+1:]
+		}
+	}
+
+	// if no error, means that the user requested `n` entries
+	if n := q.Get("n"); n != "" {
+		maxEntries, err := strconv.Atoi(n)
+		if err != nil || maxEntries < 0 {
+			th.Errors = append(th.Errors, v2.ErrorCodePaginationNumberInvalid.WithDetail(map[string]string{"n": n}))
+			return
+		}
+
+		// if there is requested more than or
+		// equal to the amount of tags we have,
+		// then set the request to equal `len(tags)`.
+		// the reason for the `=`, is so the else
+		// clause will only activate if there
+		// are tags left the user needs.
+		if maxEntries >= len(tags) {
+			maxEntries = len(tags)
+		} else if maxEntries > 0 {
+			// defined in `catalog.go`
+			urlStr, err := createLinkEntry(r.URL.String(), maxEntries, tags[maxEntries-1])
+			if err != nil {
+				th.Errors = append(th.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
+				return
+			}
+			w.Header().Set("Link", urlStr)
+		}
+
+		tags = tags[:maxEntries]
+	}
+
 	w.Header().Set("Content-Type", "application/json")
 
 	enc := json.NewEncoder(w)

registry/storage/tagstore.go

@@ -3,6 +3,7 @@ package storage
 import (
 	"context"
 	"path"
+	"sort"
 
 	"github.com/distribution/distribution/v3"
 	storagedriver "github.com/distribution/distribution/v3/registry/storage/driver"
@@ -47,6 +48,10 @@ func (ts *tagStore) All(ctx context.Context) ([]string, error) {
 		tags = append(tags, filename)
 	}
 
+	// there is no guarantee for the order,
+	// therefore sort before return.
+	sort.Strings(tags)
+
 	return tags, nil
 }