Migrate to go-acme/lego.

vendor/github.com/oracle/oci-go-sdk/common/retry.go

@@ -0,0 +1,159 @@
+package common
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"runtime"
+	"time"
+)
+
+const (
+	// UnlimitedNumAttemptsValue is the value for indicating unlimited attempts for reaching success
+	UnlimitedNumAttemptsValue = uint(0)
+
+	// number of characters contained in the generated retry token
+	generatedRetryTokenLength = 32
+)
+
+// OCIRetryableRequest represents a request that can be reissued according to the specified policy.
+type OCIRetryableRequest interface {
+	// Any retryable request must implement the OCIRequest interface
+	OCIRequest
+
+	// Each operation specifies default retry behavior. By passing no arguments to this method, the default retry
+	// behavior, as determined on a per-operation-basis, will be honored. Variadic retry policy option arguments
+	// passed to this method will override the default behavior.
+	RetryPolicy() *RetryPolicy
+}
+
+// OCIOperationResponse represents the output of an OCIOperation, with additional context of error message
+// and operation attempt number.
+type OCIOperationResponse struct {
+	// Response from OCI Operation
+	Response OCIResponse
+
+	// Error from OCI Operation
+	Error error
+
+	// Operation Attempt Number (one-based)
+	AttemptNumber uint
+}
+
+// NewOCIOperationResponse assembles an OCI Operation Response object.
+func NewOCIOperationResponse(response OCIResponse, err error, attempt uint) OCIOperationResponse {
+	return OCIOperationResponse{
+		Response:      response,
+		Error:         err,
+		AttemptNumber: attempt,
+	}
+}
+
+// RetryPolicy is the class that holds all relevant information for retrying operations.
+type RetryPolicy struct {
+	// MaximumNumberAttempts is the maximum number of times to retry a request. Zero indicates an unlimited
+	// number of attempts.
+	MaximumNumberAttempts uint
+
+	// ShouldRetryOperation inspects the http response, error, and operation attempt number, and
+	// - returns true if we should retry the operation
+	// - returns false otherwise
+	ShouldRetryOperation func(OCIOperationResponse) bool
+
+	// GetNextDuration computes the duration to pause between operation retries.
+	NextDuration func(OCIOperationResponse) time.Duration
+}
+
+// NoRetryPolicy is a helper method that assembles and returns a return policy that indicates an operation should
+// never be retried (the operation is performed exactly once).
+func NoRetryPolicy() RetryPolicy {
+	dontRetryOperation := func(OCIOperationResponse) bool { return false }
+	zeroNextDuration := func(OCIOperationResponse) time.Duration { return 0 * time.Second }
+	return NewRetryPolicy(uint(1), dontRetryOperation, zeroNextDuration)
+}
+
+// NewRetryPolicy is a helper method for assembling a Retry Policy object.
+func NewRetryPolicy(attempts uint, retryOperation func(OCIOperationResponse) bool, nextDuration func(OCIOperationResponse) time.Duration) RetryPolicy {
+	return RetryPolicy{
+		MaximumNumberAttempts: attempts,
+		ShouldRetryOperation:  retryOperation,
+		NextDuration:          nextDuration,
+	}
+}
+
+// shouldContinueIssuingRequests returns true if we should continue retrying a request, based on the current attempt
+// number and the maximum number of attempts specified, or false otherwise.
+func shouldContinueIssuingRequests(current, maximum uint) bool {
+	return maximum == UnlimitedNumAttemptsValue || current <= maximum
+}
+
+// RetryToken generates a retry token that must be included on any request passed to the Retry method.
+func RetryToken() string {
+	alphanumericChars := []rune("abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ")
+	retryToken := make([]rune, generatedRetryTokenLength)
+	for i := range retryToken {
+		retryToken[i] = alphanumericChars[rand.Intn(len(alphanumericChars))]
+	}
+	return string(retryToken)
+}
+
+// Retry is a package-level operation that executes the retryable request using the specified operation and retry policy.
+func Retry(ctx context.Context, request OCIRetryableRequest, operation OCIOperation, policy RetryPolicy) (OCIResponse, error) {
+
+	type retrierResult struct {
+		response OCIResponse
+		err      error
+	}
+
+	var response OCIResponse
+	var err error
+	retrierChannel := make(chan retrierResult)
+
+	go func() {
+
+		// Deal with panics more graciously
+		defer func() {
+			if r := recover(); r != nil {
+				stackBuffer := make([]byte, 1024)
+				bytesWritten := runtime.Stack(stackBuffer, false)
+				stack := string(stackBuffer[:bytesWritten])
+				retrierChannel <- retrierResult{nil, fmt.Errorf("panicked while retrying operation. Panic was: %s\nStack: %s", r, stack)}
+			}
+		}()
+
+		// use a one-based counter because it's easier to think about operation retry in terms of attempt numbering
+		for currentOperationAttempt := uint(1); shouldContinueIssuingRequests(currentOperationAttempt, policy.MaximumNumberAttempts); currentOperationAttempt++ {
+			Debugln(fmt.Sprintf("operation attempt #%v", currentOperationAttempt))
+			response, err = operation(ctx, request)
+			operationResponse := NewOCIOperationResponse(response, err, currentOperationAttempt)
+
+			if !policy.ShouldRetryOperation(operationResponse) {
+				// we should NOT retry operation based on response and/or error => return
+				retrierChannel <- retrierResult{response, err}
+				return
+			}
+
+			duration := policy.NextDuration(operationResponse)
+			//The following condition is kept for backwards compatibility reasons
+			if deadline, ok := ctx.Deadline(); ok && time.Now().Add(duration).After(deadline) {
+				// we want to retry the operation, but the policy is telling us to wait for a duration that exceeds
+				// the specified overall deadline for the operation => instead of waiting for however long that
+				// time period is and then aborting, abort now and save the cycles
+				retrierChannel <- retrierResult{response, DeadlineExceededByBackoff}
+				return
+			}
+			Debugln(fmt.Sprintf("waiting %v before retrying operation", duration))
+			// sleep before retrying the operation
+			<-time.After(duration)
+		}
+
+		retrierChannel <- retrierResult{nil, fmt.Errorf("maximum number of attempts exceeded (%v)", policy.MaximumNumberAttempts)}
+	}()
+
+	select {
+	case <-ctx.Done():
+		return response, ctx.Err()
+	case result := <-retrierChannel:
+		return result.response, result.err
+	}
+}