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request_retryable.go
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request_retryable.go
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package httpclient
import (
"bytes"
"fmt"
"io"
"net/http"
bosherr "github.com/cloudfoundry/bosh-utils/errors"
boshlog "github.com/cloudfoundry/bosh-utils/logger"
boshuuid "github.com/cloudfoundry/bosh-utils/uuid"
)
type RequestRetryable struct {
request *http.Request
requestID string
delegate Client
attempt int
originalBody io.ReadCloser // buffer request body to memory for retries
response *http.Response
uuidGenerator boshuuid.Generator
logger boshlog.Logger
logTag string
isResponseAttemptable func(*http.Response, error) (bool, error)
}
func NewRequestRetryable(
request *http.Request,
delegate Client,
logger boshlog.Logger,
isResponseAttemptable func(*http.Response, error) (bool, error),
) *RequestRetryable {
if isResponseAttemptable == nil {
isResponseAttemptable = defaultIsAttemptable
}
return &RequestRetryable{
request: request,
delegate: delegate,
attempt: 0,
uuidGenerator: boshuuid.NewGenerator(),
logger: logger,
logTag: "clientRetryable",
isResponseAttemptable: isResponseAttemptable,
}
}
func (r *RequestRetryable) Attempt() (bool, error) {
var err error
if r.requestID == "" {
r.requestID, err = r.uuidGenerator.Generate()
if err != nil {
return false, bosherr.WrapError(err, "Generating request uuid")
}
}
if r.attempt == 0 {
r.originalBody, err = MakeReplayable(r.request)
if err != nil {
return false, bosherr.WrapError(err, "Ensuring request can be retried")
}
} else if r.attempt > 0 && r.request.GetBody != nil {
r.request.Body, err = r.request.GetBody()
if err != nil {
if r.originalBody != nil {
r.originalBody.Close() //nolint:errcheck
}
return false, bosherr.WrapError(err, "Updating request body for retry")
}
}
// close previous attempt's response body to prevent HTTP client resource leaks
if r.response != nil {
// net/http response body early closing does not block until the body is
// properly cleaned up, which would lead to a 'request canceled' error.
// Yielding the CPU should allow the scheduler to run the cleanup tasks
// before continuing. But we found that that behavior is not deterministic,
// we instead avoid the problem altogether by reading the entire body and
// forcing an EOF.
// This should not be necessary when the following CL gets accepted:
// https://go-review.googlesource.com/c/go/+/62891
io.Copy(io.Discard, r.response.Body) //nolint:errcheck
r.response.Body.Close() //nolint:errcheck
}
r.attempt++
r.logger.Debug(r.logTag, "[requestID=%s] Requesting (attempt=%d): %s", r.requestID, r.attempt, formatRequest(r.request))
r.response, err = r.delegate.Do(r.request)
attemptable, err := r.isResponseAttemptable(r.response, err)
if !attemptable && r.originalBody != nil {
r.originalBody.Close() //nolint:errcheck
}
return attemptable, err
}
func (r *RequestRetryable) Response() *http.Response {
return r.response
}
func defaultIsAttemptable(resp *http.Response, err error) (bool, error) {
if err != nil {
return true, err
}
return !wasSuccessful(resp), nil
}
func wasSuccessful(resp *http.Response) bool {
return resp.StatusCode >= 200 && resp.StatusCode < http.StatusMultipleChoices
}
func formatRequest(req *http.Request) string {
if req == nil {
return "Request(nil)"
}
return fmt.Sprintf("Request{ Method: '%s', URL: '%s' }", req.Method, req.URL)
}
func formatResponse(resp *http.Response) string { //nolint:unused
if resp == nil {
return "Response(nil)"
}
return fmt.Sprintf("Response{ StatusCode: %d, Status: '%s' }", resp.StatusCode, resp.Status)
}
func MakeReplayable(r *http.Request) (io.ReadCloser, error) {
var err error
if r.Body == nil {
return nil, nil
} else if r.GetBody != nil {
return nil, nil
}
var originalBody = r.Body
if seekableBody, ok := r.Body.(io.ReadSeeker); ok {
r.GetBody = func() (io.ReadCloser, error) {
_, err := seekableBody.Seek(0, 0)
if err != nil {
return nil, bosherr.WrapError(err, "Seeking to beginning of seekable request body")
}
return io.NopCloser(seekableBody), nil
}
} else {
bodyBytes, err := io.ReadAll(r.Body)
if err != nil {
return originalBody, bosherr.WrapError(err, "Buffering request body")
}
r.GetBody = func() (io.ReadCloser, error) {
return io.NopCloser(bytes.NewReader(bodyBytes)), nil
}
}
r.Body, err = r.GetBody()
if err != nil {
return originalBody, bosherr.WrapError(err, "Buffering request body")
}
return originalBody, nil
}