...

Source file src/github.com/google/go-containerregistry/internal/retry/retry.go

Documentation: github.com/google/go-containerregistry/internal/retry

     1  // Copyright 2019 Google LLC All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //    http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package retry provides methods for retrying operations. It is a thin wrapper
    16  // around k8s.io/apimachinery/pkg/util/wait to make certain operations easier.
    17  package retry
    18  
    19  import (
    20  	"context"
    21  	"errors"
    22  	"fmt"
    23  
    24  	"github.com/google/go-containerregistry/internal/retry/wait"
    25  )
    26  
    27  // Backoff is an alias of our own wait.Backoff to avoid name conflicts with
    28  // the kubernetes wait package. Typing retry.Backoff is aesier than fixing
    29  // the wrong import every time you use wait.Backoff.
    30  type Backoff = wait.Backoff
    31  
    32  // This is implemented by several errors in the net package as well as our
    33  // transport.Error.
    34  type temporary interface {
    35  	Temporary() bool
    36  }
    37  
    38  // IsTemporary returns true if err implements Temporary() and it returns true.
    39  func IsTemporary(err error) bool {
    40  	if errors.Is(err, context.DeadlineExceeded) {
    41  		return false
    42  	}
    43  	if te, ok := err.(temporary); ok && te.Temporary() {
    44  		return true
    45  	}
    46  	return false
    47  }
    48  
    49  // IsNotNil returns true if err is not nil.
    50  func IsNotNil(err error) bool {
    51  	return err != nil
    52  }
    53  
    54  // Predicate determines whether an error should be retried.
    55  type Predicate func(error) (retry bool)
    56  
    57  // Retry retries a given function, f, until a predicate is satisfied, using
    58  // exponential backoff. If the predicate is never satisfied, it will return the
    59  // last error returned by f.
    60  func Retry(f func() error, p Predicate, backoff wait.Backoff) (err error) {
    61  	if f == nil {
    62  		return fmt.Errorf("nil f passed to retry")
    63  	}
    64  	if p == nil {
    65  		return fmt.Errorf("nil p passed to retry")
    66  	}
    67  
    68  	condition := func() (bool, error) {
    69  		err = f()
    70  		if p(err) {
    71  			return false, nil
    72  		}
    73  		return true, err
    74  	}
    75  
    76  	wait.ExponentialBackoff(backoff, condition)
    77  	return
    78  }
    79  
    80  type contextKey string
    81  
    82  var key = contextKey("never")
    83  
    84  // Never returns a context that signals something should not be retried.
    85  // This is a hack and can be used to communicate across package boundaries
    86  // to avoid retry amplification.
    87  func Never(ctx context.Context) context.Context {
    88  	return context.WithValue(ctx, key, true)
    89  }
    90  
    91  // Ever returns true if the context was wrapped by Never.
    92  func Ever(ctx context.Context) bool {
    93  	return ctx.Value(key) == nil
    94  }
    95  

View as plain text