reference: implement Sort()

This upstreams `Sort()` as originally implemented in containerd in
https://github.com/containerd/containerd/0886ceaea2470edc7339dfc5ebe0e3257ae84d06

From that commit:

> Fix reference ordering in CRI image store
>
> Currently image references end up being stored in a
> random order due to the way maps are iterated through
> in Go. This leads to inconsistent identifiers being
> resolved when a single reference is needed to identify
> an image and the ordering of the references is used for
> the selection.
>
> Sort references in a consistent and ranked manner,
> from higher information formats to lower.
>
> Note: A `name + tag` reference is considered higher
> information than a `name + digest` reference since a
> registry may be used to resolve the digest from a
> `name + tag` reference.

Co-Authored-by: Derek McGowan <derek@mcg.dev>
Co-Authored-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Derek McGowan 2021-03-22 22:18:43 -07:00 committed by Sebastiaan van Stijn
parent fee8c686bb
commit 1052518d9f
No known key found for this signature in database
GPG key ID: 76698F39D527CE8C
2 changed files with 156 additions and 0 deletions

73
reference/sort.go Normal file
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/*
Copyright The containerd Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package reference
import (
"sort"
)
// Sort sorts string references preferring higher information references
// The precedence is as follows:
// 1. Name + Tag + Digest
// 2. Name + Tag
// 3. Name + Digest
// 4. Name
// 5. Digest
// 6. Parse error
func Sort(references []string) []string {
var prefs []Reference
var bad []string
for _, ref := range references {
pref, err := ParseAnyReference(ref)
if err != nil {
bad = append(bad, ref)
} else {
prefs = append(prefs, pref)
}
}
sort.Slice(prefs, func(a, b int) bool {
ar := refRank(prefs[a])
br := refRank(prefs[b])
if ar == br {
return prefs[a].String() < prefs[b].String()
}
return ar < br
})
sort.Strings(bad)
var refs []string
for _, pref := range prefs {
refs = append(refs, pref.String())
}
return append(refs, bad...)
}
func refRank(ref Reference) uint8 {
if _, ok := ref.(Named); ok {
if _, ok = ref.(Tagged); ok {
if _, ok = ref.(Digested); ok {
return 1
}
return 2
}
if _, ok = ref.(Digested); ok {
return 3
}
return 4
}
return 5
}

83
reference/sort_test.go Normal file
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/*
Copyright The containerd Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package reference
import (
"io"
"math/rand"
"testing"
"github.com/opencontainers/go-digest"
)
func TestReferenceSorting(t *testing.T) {
digested := func(seed int64) string {
b, err := io.ReadAll(io.LimitReader(rand.New(rand.NewSource(seed)), 64))
if err != nil {
panic(err)
}
return digest.FromBytes(b).String()
}
// Add z. prefix to string sort after "sha256:"
r1 := func(name, tag string, seed int64) string {
return "z.containerd.io/" + name + ":" + tag + "@" + digested(seed)
}
r2 := func(name, tag string) string {
return "z.containerd.io/" + name + ":" + tag
}
r3 := func(name string, seed int64) string {
return "z.containerd.io/" + name + "@" + digested(seed)
}
for i, tc := range []struct {
unsorted []string
expected []string
}{
{
unsorted: []string{r2("name", "latest"), r3("name", 1), r1("name", "latest", 1)},
expected: []string{r1("name", "latest", 1), r2("name", "latest"), r3("name", 1)},
},
{
unsorted: []string{"can't parse this:latest", r3("name", 1), r2("name", "latest")},
expected: []string{r2("name", "latest"), r3("name", 1), "can't parse this:latest"},
},
{
unsorted: []string{digested(1), r3("name", 1), r2("name", "latest")},
expected: []string{r2("name", "latest"), r3("name", 1), digested(1)},
},
{
unsorted: []string{r2("name", "tag2"), r2("name", "tag3"), r2("name", "tag1")},
expected: []string{r2("name", "tag1"), r2("name", "tag2"), r2("name", "tag3")},
},
{
unsorted: []string{r2("name-2", "tag"), r2("name-3", "tag"), r2("name-1", "tag")},
expected: []string{r2("name-1", "tag"), r2("name-2", "tag"), r2("name-3", "tag")},
},
} {
sorted := Sort(tc.unsorted)
if len(sorted) != len(tc.expected) {
t.Errorf("[%d]: Mismatched sized, got %d, expected %d", i, len(sorted), len(tc.expected))
continue
}
for j := range sorted {
if sorted[j] != tc.expected[j] {
t.Errorf("[%d]: Wrong value at %d, got %q, expected %q", i, j, sorted[j], tc.expected[j])
break
}
}
}
}