Add function for configuring transport with retry backoff

This pr also splits LoginWithCredentials into a sub-function
GetAuthFromCredentials that returns the Authenticator. This
function can be used to get the authenticator for constructing
the retry transport.

Signed-off-by: Somtochi Onyekwere <[email protected]>

oci/client/login.go

@@ -34,10 +34,22 @@ import (
 // LoginWithCredentials configures the client with static credentials, accepts a single token
 // or a user:password format.
 func (c *Client) LoginWithCredentials(credentials string) error {
+	auth, err := GetAuthFromCredentials(credentials)
+	if err != nil {
+		return err
+	}
+
+	c.options = append(c.options, crane.WithAuth(auth))
+	return nil
+}
+
+// GetAuthFromCredentials returns an authn.Authenticator for the static credentials, accepts a single token
+// or a user:password format.
+func GetAuthFromCredentials(credentials string) (authn.Authenticator, error) {
 	var authConfig authn.AuthConfig
 
 	if credentials == "" {
-		return errors.New("credentials cannot be empty")
+		return nil, errors.New("credentials cannot be empty")
 	}
 
 	parts := strings.SplitN(credentials, ":", 2)
@@ -48,8 +60,7 @@ func (c *Client) LoginWithCredentials(credentials string) error {
 		authConfig = authn.AuthConfig{Username: parts[0], Password: parts[1]}
 	}
 
-	c.options = append(c.options, crane.WithAuth(authn.FromConfig(authConfig)))
-	return nil
+	return authn.FromConfig(authConfig), nil
 }
 
 // LoginWithProvider configures the client to log in to the specified provider

oci/client/retry_transport.go

@@ -0,0 +1,91 @@
+/*
+Copyright 2023 The Flux authors
+Copyright 2018 Google LLC All Rights Reserved.
+
+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 client
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net/http"
+	"syscall"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/crane"
+	"github.com/google/go-containerregistry/pkg/logs"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/google/go-containerregistry/pkg/v1/remote/transport"
+
+	"github.com/fluxcd/pkg/oci"
+)
+
+// WithRetryTransport returns a crane.Option for setting transport that uses the  backoff for retries
+//
+// Most parts(including the functions below) are copied from https://github.com/google/go-containerregistry/blob/v0.14.0/pkg/v1/remote/options.go#L152
+// so we have the same transport used in the library but with a different retry backoff.
+func WithRetryTransport(ctx context.Context, ref name.Reference, auth authn.Authenticator, backoff remote.Backoff, scopes []string) (crane.Option, error) {
+	var retryTransport http.RoundTripper
+	retryTransport = remote.DefaultTransport.(*http.Transport).Clone()
+	if logs.Enabled(logs.Debug) {
+		retryTransport = transport.NewLogger(retryTransport)
+	}
+	retryTransport = transport.NewRetry(retryTransport,
+		transport.WithRetryPredicate(defaultRetryPredicate),
+		transport.WithRetryStatusCodes(retryableStatusCodes...),
+		transport.WithRetryBackoff(backoff))
+	retryTransport = transport.NewUserAgent(retryTransport, oci.UserAgent)
+
+	t, err := transport.NewWithContext(ctx, ref.Context().Registry, auth, retryTransport, scopes)
+	if err != nil {
+		return nil, err
+	}
+	return crane.WithTransport(t), nil
+}
+
+var defaultRetryPredicate = func(err error) bool {
+	// Various failure modes here, as we're often reading from and writing to
+	// the network.
+	if isTemporary(err) || errors.Is(err, io.ErrUnexpectedEOF) || errors.Is(err, io.EOF) || errors.Is(err, syscall.EPIPE) || errors.Is(err, syscall.ECONNRESET) {
+		logs.Warn.Printf("retrying %v", err)
+		return true
+	}
+	return false
+}
+
+type temporary interface {
+	Temporary() bool
+}
+
+// isTemporary returns true if err implements Temporary() and it returns true.
+func isTemporary(err error) bool {
+	if errors.Is(err, context.DeadlineExceeded) {
+		return false
+	}
+	if te, ok := err.(temporary); ok && te.Temporary() {
+		return true
+	}
+	return false
+}
+
+var retryableStatusCodes = []int{
+	http.StatusRequestTimeout,
+	http.StatusInternalServerError,
+	http.StatusBadGateway,
+	http.StatusServiceUnavailable,
+	http.StatusGatewayTimeout,
+}