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package request
import (
"fmt"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/awsutil"
)
// WaiterResourceNotReadyErrorCode is the error code returned by a waiter when
// the waiter's max attempts have been exhausted.
const WaiterResourceNotReadyErrorCode = "ResourceNotReady"
// A WaiterOption is a function that will update the Waiter value's fields to
// configure the waiter.
type WaiterOption func(*Waiter)
// WithWaiterMaxAttempts returns the maximum number of times the waiter should
// attempt to check the resource for the target state.
func WithWaiterMaxAttempts(max int) WaiterOption {
return func(w *Waiter) {
w.MaxAttempts = max
}
}
// WaiterDelay will return a delay the waiter should pause between attempts to
// check the resource state. The passed in attempt is the number of times the
// Waiter has checked the resource state.
//
// Attempt is the number of attempts the Waiter has made checking the resource
// state.
type WaiterDelay func(attempt int) time.Duration
// ConstantWaiterDelay returns a WaiterDelay that will always return a constant
// delay the waiter should use between attempts. It ignores the number of
// attempts made.
func ConstantWaiterDelay(delay time.Duration) WaiterDelay {
return func(attempt int) time.Duration {
return delay
}
}
// WithWaiterDelay will set the Waiter to use the WaiterDelay passed in.
func WithWaiterDelay(delayer WaiterDelay) WaiterOption {
return func(w *Waiter) {
w.Delay = delayer
}
}
// WithWaiterLogger returns a waiter option to set the logger a waiter
// should use to log warnings and errors to.
func WithWaiterLogger(logger aws.Logger) WaiterOption {
return func(w *Waiter) {
w.Logger = logger
}
}
// WithWaiterRequestOptions returns a waiter option setting the request
// options for each request the waiter makes. Appends to waiter's request
// options already set.
func WithWaiterRequestOptions(opts ...Option) WaiterOption {
return func(w *Waiter) {
w.RequestOptions = append(w.RequestOptions, opts...)
}
}
// A Waiter provides the functionality to perform a blocking call which will
// wait for a resource state to be satisfied by a service.
//
// This type should not be used directly. The API operations provided in the
// service packages prefixed with "WaitUntil" should be used instead.
type Waiter struct {
Name string
Acceptors []WaiterAcceptor
Logger aws.Logger
MaxAttempts int
Delay WaiterDelay
RequestOptions []Option
NewRequest func([]Option) (*Request, error)
SleepWithContext func(aws.Context, time.Duration) error
}
// ApplyOptions updates the waiter with the list of waiter options provided.
func (w *Waiter) ApplyOptions(opts ...WaiterOption) {
for _, fn := range opts {
fn(w)
}
}
// WaiterState are states the waiter uses based on WaiterAcceptor definitions
// to identify if the resource state the waiter is waiting on has occurred.
type WaiterState int
// String returns the string representation of the waiter state.
func (s WaiterState) String() string {
switch s {
case SuccessWaiterState:
return "success"
case FailureWaiterState:
return "failure"
case RetryWaiterState:
return "retry"
default:
return "unknown waiter state"
}
}
// States the waiter acceptors will use to identify target resource states.
const (
SuccessWaiterState WaiterState = iota // waiter successful
FailureWaiterState // waiter failed
RetryWaiterState // waiter needs to be retried
)
// WaiterMatchMode is the mode that the waiter will use to match the WaiterAcceptor
// definition's Expected attribute.
type WaiterMatchMode int
// Modes the waiter will use when inspecting API response to identify target
// resource states.
const (
PathAllWaiterMatch WaiterMatchMode = iota // match on all paths
PathWaiterMatch // match on specific path
PathAnyWaiterMatch // match on any path
PathListWaiterMatch // match on list of paths
StatusWaiterMatch // match on status code
ErrorWaiterMatch // match on error
)
// String returns the string representation of the waiter match mode.
func (m WaiterMatchMode) String() string {
switch m {
case PathAllWaiterMatch:
return "pathAll"
case PathWaiterMatch:
return "path"
case PathAnyWaiterMatch:
return "pathAny"
case PathListWaiterMatch:
return "pathList"
case StatusWaiterMatch:
return "status"
case ErrorWaiterMatch:
return "error"
default:
return "unknown waiter match mode"
}
}
// WaitWithContext will make requests for the API operation using NewRequest to
// build API requests. The request's response will be compared against the
// Waiter's Acceptors to determine the successful state of the resource the
// waiter is inspecting.
//
// The passed in context must not be nil. If it is nil a panic will occur. The
// Context will be used to cancel the waiter's pending requests and retry delays.
// Use aws.BackgroundContext if no context is available.
//
// The waiter will continue until the target state defined by the Acceptors,
// or the max attempts expires.
//
// Will return the WaiterResourceNotReadyErrorCode error code if the waiter's
// retryer ShouldRetry returns false. This normally will happen when the max
// wait attempts expires.
func (w Waiter) WaitWithContext(ctx aws.Context) error {
for attempt := 1; ; attempt++ {
req, err := w.NewRequest(w.RequestOptions)
if err != nil {
waiterLogf(w.Logger, "unable to create request %v", err)
return err
}
req.Handlers.Build.PushBack(MakeAddToUserAgentFreeFormHandler("Waiter"))
err = req.Send()
// See if any of the acceptors match the request's response, or error
for _, a := range w.Acceptors {
if matched, matchErr := a.match(w.Name, w.Logger, req, err); matched {
return matchErr
}
}
// The Waiter should only check the resource state MaxAttempts times
// This is here instead of in the for loop above to prevent delaying
// unnecessary when the waiter will not retry.
if attempt == w.MaxAttempts {
break
}
// Delay to wait before inspecting the resource again
delay := w.Delay(attempt)
if sleepFn := req.Config.SleepDelay; sleepFn != nil {
// Support SleepDelay for backwards compatibility and testing
sleepFn(delay)
} else {
sleepCtxFn := w.SleepWithContext
if sleepCtxFn == nil {
sleepCtxFn = aws.SleepWithContext
}
if err := sleepCtxFn(ctx, delay); err != nil {
return awserr.New(CanceledErrorCode, "waiter context canceled", err)
}
}
}
return awserr.New(WaiterResourceNotReadyErrorCode, "exceeded wait attempts", nil)
}
// A WaiterAcceptor provides the information needed to wait for an API operation
// to complete.
type WaiterAcceptor struct {
State WaiterState
Matcher WaiterMatchMode
Argument string
Expected interface{}
}
// match returns if the acceptor found a match with the passed in request
// or error. True is returned if the acceptor made a match, error is returned
// if there was an error attempting to perform the match.
func (a *WaiterAcceptor) match(name string, l aws.Logger, req *Request, err error) (bool, error) {
result := false
var vals []interface{}
switch a.Matcher {
case PathAllWaiterMatch, PathWaiterMatch:
// Require all matches to be equal for result to match
vals, _ = awsutil.ValuesAtPath(req.Data, a.Argument)
if len(vals) == 0 {
break
}
result = true
for _, val := range vals {
if !awsutil.DeepEqual(val, a.Expected) {
result = false
break
}
}
case PathAnyWaiterMatch:
// Only a single match needs to equal for the result to match
vals, _ = awsutil.ValuesAtPath(req.Data, a.Argument)
for _, val := range vals {
if awsutil.DeepEqual(val, a.Expected) {
result = true
break
}
}
case PathListWaiterMatch:
// ignored matcher
case StatusWaiterMatch:
s := a.Expected.(int)
result = s == req.HTTPResponse.StatusCode
case ErrorWaiterMatch:
if aerr, ok := err.(awserr.Error); ok {
result = aerr.Code() == a.Expected.(string)
}
default:
waiterLogf(l, "WARNING: Waiter %s encountered unexpected matcher: %s",
name, a.Matcher)
}
if !result {
// If there was no matching result found there is nothing more to do
// for this response, retry the request.
return false, nil
}
switch a.State {
case SuccessWaiterState:
// waiter completed
return true, nil
case FailureWaiterState:
// Waiter failure state triggered
return true, awserr.New(WaiterResourceNotReadyErrorCode,
"failed waiting for successful resource state", err)
case RetryWaiterState:
// clear the error and retry the operation
return false, nil
default:
waiterLogf(l, "WARNING: Waiter %s encountered unexpected state: %s",
name, a.State)
return false, nil
}
}
func waiterLogf(logger aws.Logger, msg string, args ...interface{}) {
if logger != nil {
logger.Log(fmt.Sprintf(msg, args...))
}
}
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