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set digest-only for each mirror
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Close: #1407
Add the `digest-only` field to each mirror table, so it will
be configured for each mirror instead of for primary registry.
For the same primary registry, it can support both digest only pull
and tag allowed pull.

The `mirror-by-digest-only` for primary is still allowed configuring,
and it is honored for compatibility

Signed-off-by: Qi Wang <qiwan@redhat.com>
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QiWang19 committed Dec 10, 2021
1 parent 6f3c845 commit ffb4bb3
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Showing 4 changed files with 148 additions and 9 deletions.
12 changes: 10 additions & 2 deletions docs/containers-registries.conf.5.md
Original file line number Diff line number Diff line change
Expand Up @@ -108,16 +108,24 @@ Each TOML table in the `mirror` array can contain the following fields, with the
as if specified in the `[[registry]]` TOML table directly:
- `location`
- `insecure`
- `digest-only`

`mirror-by-digest-only`
: `true` or `false`.
If `true`, mirrors will only be used during pulling if the image reference includes a digest.
Note that if this is `true`, images referenced by a tag will only use the primary
registry, failing if that registry is not accessible.

`digest-only`: `true` or `false`.
: if `true` an individual mirror will only be used during pulling if the image reference includes a digest.
Note that digest-only will be overridden if mirror-by-digest is set for the entire registry.
Also note that if all mirrors in the `mirror` array have `digest-only = true`, images referenced by a tag will only use the primary
registry, failing if that registry is not accessible.

Referencing an image by digest ensures that the same is always used
(whereas referencing an image by a tag may cause different registries to return
different images if the tag mapping is out of sync).

Note that if this is `true`, images referenced by a tag will only use the primary
registry, failing if that registry is not accessible.

*Note*: Redirection and mirrors are currently processed only when reading images, not when pushing
to a registry; that may change in the future.
Expand Down
35 changes: 28 additions & 7 deletions pkg/sysregistriesv2/system_registries_v2.go
Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,12 @@ type Endpoint struct {
// If true, certs verification will be skipped and HTTP (non-TLS)
// connections will be allowed.
Insecure bool `toml:"insecure,omitempty"`
// If true, the mirror will only be used for digest pulls. Pulling images by
// tag can potentially yield different images, depending on which endpoint
// we pull from. Forcing digest-pulls for mirrors avoids that issue.
// This only applies to the mirror of the primary registry.
// If mirror-by-digest-only is set for the primary registry, mirror-by-digest-only is honored.
DigestOnly bool `toml:"digest-only,omitempty"`
}

// userRegistriesFile is the path to the per user registry configuration file.
Expand Down Expand Up @@ -130,16 +136,27 @@ type PullSource struct {
// reference.
func (r *Registry) PullSourcesFromReference(ref reference.Named) ([]PullSource, error) {
var endpoints []Endpoint

_, isDigested := ref.(reference.Canonical)
if r.MirrorByDigestOnly {
// Only use mirrors when the reference is a digest one.
if _, isDigested := ref.(reference.Canonical); isDigested {
// Only use mirrors when the reference is a digested one.
if isDigested {
endpoints = append(r.Mirrors, r.Endpoint)
} else {
endpoints = []Endpoint{r.Endpoint}
}
} else {
endpoints = append(r.Mirrors, r.Endpoint)
// check digest-only for each mirror if non mirror-by-digest-only set, since mirror-by-digest-only is honored
for _, mirror := range r.Mirrors {
if mirror.DigestOnly {
if isDigested {
// Only use the mirror when the reference is a digested one.
endpoints = append(endpoints, mirror)
}
} else {
endpoints = append(endpoints, mirror)
}
}
endpoints = append(endpoints, r.Endpoint)
}

sources := []PullSource{}
Expand Down Expand Up @@ -919,15 +936,19 @@ func loadConfigFile(path string, forceV2 bool) (*parsedConfig, error) {
res.shortNameMode = types.ShortNameModeInvalid
}

// Valid wildcarded prefixes must be in the format: *.example.com
// FIXME: Move to postProcessRegistries
// https://github.com/containers/image/pull/1191#discussion_r610623829
for i := range res.partialV2.Registries {
// Valid wildcarded prefixes must be in the format: *.example.com
// FIXME: Move to postProcessRegistries
// https://github.com/containers/image/pull/1191#discussion_r610623829
prefix := res.partialV2.Registries[i].Prefix
if strings.HasPrefix(prefix, "*.") && strings.ContainsAny(prefix, "/@:") {
msg := fmt.Sprintf("Wildcarded prefix should be in the format: *.example.com. Current prefix %q is incorrectly formatted", prefix)
return nil, &InvalidRegistries{s: msg}
}
// validate the mirror usage settings does not apply to primary registry
if res.partialV2.Registries[i].DigestOnly {
return nil, fmt.Errorf("digest-only does not apply to primary registry %s", prefix)
}
}

// Parse and validate short-name aliases.
Expand Down
66 changes: 66 additions & 0 deletions pkg/sysregistriesv2/system_registries_v2_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -675,6 +675,72 @@ func TestPullSourcesFromReference(t *testing.T) {
assert.Equal(t, 1, len(pullSources))
}

func TestPullSourcesMirrorFromReference(t *testing.T) {
sys := &types.SystemContext{
SystemRegistriesConfPath: "testdata/pull-sources-mirror-reference.conf",
SystemRegistriesConfDirPath: "testdata/this-does-not-exist",
}
registries, err := GetRegistries(sys)
assert.Nil(t, err)
assert.Equal(t, 4, len(registries))

for _, tc := range []struct {
registry string
digestRef string
digestSources int
tagRef string
tagSources int
}{
// Registry A has mirrors allow any kind of pull
{
"registry-a.com/foo/image:latest",
"registry-a.com/foo/image@sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
3,
"registry-a.com/foo/image:aaa",
3,
},
// Registry B has mirrors allow digests pull only
{
"registry-b.com/foo/image:latest",
"registry-b.com/foo/image@sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
3,
"registry-b.com/foo/image:aaa",
1,
},
// Registry C has a mirror allows digest pull only and a mirror allows any kind of pull
{
"registry-c.com/foo/image:latest",
"registry-c.com/foo/image@sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
3,
"registry-c.com/foo/image:aaa",
2,
},
// Registry D set mirror-by-digest-only, honor this configuration for registry
// Regsitry D has no digest-only set for mirrors table
{
"registry-d.com/foo/image:latest",
"registry-d.com/foo/image@sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
3,
"registry-d.com/foo/image:aaa",
1,
},
} {
registry, err := FindRegistry(sys, tc.registry)
assert.Nil(t, err)
assert.NotNil(t, registry)
// Digest
referenceDigest := toNamedRef(t, tc.digestRef)
pullSource, err := registry.PullSourcesFromReference(referenceDigest)
assert.Nil(t, err)
assert.Equal(t, tc.digestSources, len(pullSource))
// Tag
referenceTag := toNamedRef(t, tc.tagRef)
pullSource, err = registry.PullSourcesFromReference(referenceTag)
assert.Nil(t, err)
assert.Equal(t, tc.tagSources, len(pullSource))
}
}

func TestTryUpdatingCache(t *testing.T) {
ctx := &types.SystemContext{
SystemRegistriesConfPath: "testdata/try-update-cache-valid.conf",
Expand Down
44 changes: 44 additions & 0 deletions pkg/sysregistriesv2/testdata/pull-sources-mirror-reference.conf
Original file line number Diff line number Diff line change
@@ -0,0 +1,44 @@
[[registry]]
prefix = "registry-a.com/foo"
location = "registry-a.com/bar"

[[registry.mirror]]
location = "mirror-1.registry-a.com"

[[registry.mirror]]
location = "mirror-2.registry-a.com"
insecure = true

[[registry]]
prefix = "registry-b.com/foo"
location = "registry-b.com/bar"

[[registry.mirror]]
digest-only = true
location = "mirror-1.registry-b.com"

[[registry.mirror]]
digest-only = true
location = "mirror-2.registry-b.com"

[[registry]]
prefix = "registry-c.com/foo"
location = "registry-c.com/bar"

[[registry.mirror]]
location = "mirror-1.registry-c.com"

[[registry.mirror]]
digest-only = true
location = "mirror-2.registry-c.com"

[[registry]]
prefix = "registry-d.com/foo"
location = "registry-d.com/bar"
mirror-by-digest-only = true

[[registry.mirror]]
location = "mirror-1.registry-d.com"

[[registry.mirror]]
location = "mirror-2.registry-d.com"

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