Add API retry functionality in mc admin (#7602)

pkg/madmin/api-error-response.go

@@ -77,6 +77,28 @@ func httpRespToErrorResponse(resp *http.Response) error {
 	return errResp
 }
 
+// ToErrorResponse - Returns parsed ErrorResponse struct from body and
+// http headers.
+//
+// For example:
+//
+//   import admin "github.com/minio/minio/pkg/madmin"
+//   ...
+//   ...
+//   ss, err := adm.ServiceStatus(...)
+//   if err != nil {
+//      resp := admin.ToErrorResponse(err)
+//   }
+//   ...
+func ToErrorResponse(err error) ErrorResponse {
+	switch err := err.(type) {
+	case ErrorResponse:
+		return err
+	default:
+		return ErrorResponse{}
+	}
+}
+
 // ErrInvalidArgument - Invalid argument response.
 func ErrInvalidArgument(message string) error {
 	return ErrorResponse{

pkg/madmin/api.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"math/rand"
 	"net/http"
 	"net/http/httputil"
 	"net/url"
@@ -29,6 +30,7 @@ import (
 	"regexp"
 	"runtime"
 	"strings"
+	"time"
 
 	"github.com/minio/minio-go/pkg/s3signer"
 	"github.com/minio/minio-go/pkg/s3utils"
@@ -57,6 +59,8 @@ type AdminClient struct {
 	// Needs allocation.
 	httpClient *http.Client
 
+	random *rand.Rand
+
 	// Advanced functionality.
 	isTraceEnabled bool
 	traceOutput    io.Writer
@@ -107,6 +111,8 @@ func privateNew(endpoint, accessKeyID, secretAccessKey string, secure bool) (*Ad
 		httpClient: &http.Client{
 			Transport: http.DefaultTransport,
 		},
+		// Introduce a new locked random seed.
+		random: rand.New(&lockedRandSource{src: rand.NewSource(time.Now().UTC().UnixNano())}),
 	}
 
 	// Return.
@@ -315,6 +321,7 @@ var successStatus = []int{
 // request upon any error up to maxRetries attempts in a binomially
 // delayed manner using a standard back off algorithm.
 func (adm AdminClient) executeMethod(method string, reqData requestData) (res *http.Response, err error) {
+	var reqRetry = MaxRetry // Indicates how many times we can retry the request
 
 	// Create a done channel to control 'ListObjects' go routine.
 	doneCh := make(chan struct{}, 1)
@@ -322,39 +329,63 @@ func (adm AdminClient) executeMethod(method string, reqData requestData) (res *h
 	// Indicate to our routine to exit cleanly upon return.
 	defer close(doneCh)
 
-	// Instantiate a new request.
+	for range adm.newRetryTimer(reqRetry, DefaultRetryUnit, DefaultRetryCap, MaxJitter, doneCh) {
-	var req *http.Request
+		// Instantiate a new request.
-	req, err = adm.newRequest(method, reqData)
+		var req *http.Request
-	if err != nil {
+		req, err = adm.newRequest(method, reqData)
-		return nil, err
+		if err != nil {
-	}
+			return nil, err
-
-	// Initiate the request.
-	res, err = adm.do(req)
-	if err != nil {
-		return nil, err
-	}
-
-	// For any known successful http status, return quickly.
-	for _, httpStatus := range successStatus {
-		if httpStatus == res.StatusCode {
-			return res, nil
 		}
+
+		// Initiate the request.
+		res, err = adm.do(req)
+		if err != nil {
+			// For supported http requests errors verify.
+			if isHTTPReqErrorRetryable(err) {
+				continue // Retry.
+			}
+			// For other errors, return here no need to retry.
+			return nil, err
+		}
+
+		// For any known successful http status, return quickly.
+		for _, httpStatus := range successStatus {
+			if httpStatus == res.StatusCode {
+				return res, nil
+			}
+		}
+
+		// Read the body to be saved later.
+		errBodyBytes, err := ioutil.ReadAll(res.Body)
+		// res.Body should be closed
+		closeResponse(res)
+		if err != nil {
+			return nil, err
+		}
+
+		// Save the body.
+		errBodySeeker := bytes.NewReader(errBodyBytes)
+		res.Body = ioutil.NopCloser(errBodySeeker)
+
+		// For errors verify if its retryable otherwise fail quickly.
+		errResponse := ToErrorResponse(httpRespToErrorResponse(res))
+
+		// Save the body back again.
+		errBodySeeker.Seek(0, 0) // Seek back to starting point.
+		res.Body = ioutil.NopCloser(errBodySeeker)
+
+		// Verify if error response code is retryable.
+		if isS3CodeRetryable(errResponse.Code) {
+			continue // Retry.
+		}
+
+		// Verify if http status code is retryable.
+		if isHTTPStatusRetryable(res.StatusCode) {
+			continue // Retry.
+		}
+
+		break
 	}
-
-	// Read the body to be saved later.
-	errBodyBytes, err := ioutil.ReadAll(res.Body)
-	if err != nil {
-		return nil, err
-	}
-	// Save the body.
-	errBodySeeker := bytes.NewReader(errBodyBytes)
-	res.Body = ioutil.NopCloser(errBodySeeker)
-
-	// Save the body back again.
-	errBodySeeker.Seek(0, 0) // Seek back to starting point.
-	res.Body = ioutil.NopCloser(errBodySeeker)
-
 	return res, err
 }
 

pkg/madmin/retry.go

@@ -0,0 +1,175 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
+ *
+ * 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 madmin
+
+import (
+	"math/rand"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+)
+
+// MaxRetry is the maximum number of retries before stopping.
+var MaxRetry = 10
+
+// MaxJitter will randomize over the full exponential backoff time
+const MaxJitter = 1.0
+
+// NoJitter disables the use of jitter for randomizing the exponential backoff time
+const NoJitter = 0.0
+
+// DefaultRetryUnit - default unit multiplicative per retry.
+// defaults to 1 second.
+const DefaultRetryUnit = time.Second
+
+// DefaultRetryCap - Each retry attempt never waits no longer than
+// this maximum time duration.
+const DefaultRetryCap = time.Second * 30
+
+// lockedRandSource provides protected rand source, implements rand.Source interface.
+type lockedRandSource struct {
+	lk  sync.Mutex
+	src rand.Source
+}
+
+// Int63 returns a non-negative pseudo-random 63-bit integer as an int64.
+func (r *lockedRandSource) Int63() (n int64) {
+	r.lk.Lock()
+	n = r.src.Int63()
+	r.lk.Unlock()
+	return
+}
+
+// Seed uses the provided seed value to initialize the generator to a
+// deterministic state.
+func (r *lockedRandSource) Seed(seed int64) {
+	r.lk.Lock()
+	r.src.Seed(seed)
+	r.lk.Unlock()
+}
+
+// newRetryTimer creates a timer with exponentially increasing
+// delays until the maximum retry attempts are reached.
+func (adm AdminClient) newRetryTimer(maxRetry int, unit time.Duration, cap time.Duration, jitter float64, doneCh chan struct{}) <-chan int {
+	attemptCh := make(chan int)
+
+	// computes the exponential backoff duration according to
+	// https://www.awsarchitectureblog.com/2015/03/backoff.html
+	exponentialBackoffWait := func(attempt int) time.Duration {
+		// normalize jitter to the range [0, 1.0]
+		if jitter < NoJitter {
+			jitter = NoJitter
+		}
+		if jitter > MaxJitter {
+			jitter = MaxJitter
+		}
+
+		//sleep = random_between(0, min(cap, base * 2 ** attempt))
+		sleep := unit * time.Duration(1<<uint(attempt))
+		if sleep > cap {
+			sleep = cap
+		}
+		if jitter != NoJitter {
+			sleep -= time.Duration(adm.random.Float64() * float64(sleep) * jitter)
+		}
+		return sleep
+	}
+
+	go func() {
+		defer close(attemptCh)
+		for i := 0; i < maxRetry; i++ {
+			select {
+			// Attempts start from 1.
+			case attemptCh <- i + 1:
+			case <-doneCh:
+				// Stop the routine.
+				return
+			}
+			time.Sleep(exponentialBackoffWait(i))
+		}
+	}()
+	return attemptCh
+}
+
+// isHTTPReqErrorRetryable - is http requests error retryable, such
+// as i/o timeout, connection broken etc..
+func isHTTPReqErrorRetryable(err error) bool {
+	if err == nil {
+		return false
+	}
+	switch e := err.(type) {
+	case *url.Error:
+		switch e.Err.(type) {
+		case *net.DNSError, *net.OpError, net.UnknownNetworkError:
+			return true
+		}
+		if strings.Contains(err.Error(), "Connection closed by foreign host") {
+			return true
+		} else if strings.Contains(err.Error(), "net/http: TLS handshake timeout") {
+			// If error is - tlsHandshakeTimeoutError, retry.
+			return true
+		} else if strings.Contains(err.Error(), "i/o timeout") {
+			// If error is - tcp timeoutError, retry.
+			return true
+		} else if strings.Contains(err.Error(), "connection timed out") {
+			// If err is a net.Dial timeout, retry.
+			return true
+		} else if strings.Contains(err.Error(), "net/http: HTTP/1.x transport connection broken") {
+			// If error is transport connection broken, retry.
+			return true
+		}
+	}
+	return false
+}
+
+// List of AWS S3 error codes which are retryable.
+var retryableS3Codes = map[string]struct{}{
+	"RequestError":         {},
+	"RequestTimeout":       {},
+	"Throttling":           {},
+	"ThrottlingException":  {},
+	"RequestLimitExceeded": {},
+	"RequestThrottled":     {},
+	"InternalError":        {},
+	"SlowDown":             {},
+	// Add more AWS S3 codes here.
+}
+
+// isS3CodeRetryable - is s3 error code retryable.
+func isS3CodeRetryable(s3Code string) (ok bool) {
+	_, ok = retryableS3Codes[s3Code]
+	return ok
+}
+
+// List of HTTP status codes which are retryable.
+var retryableHTTPStatusCodes = map[int]struct{}{
+	http.StatusTooManyRequests:     {},
+	http.StatusInternalServerError: {},
+	http.StatusBadGateway:          {},
+	http.StatusServiceUnavailable:  {},
+	// Add more HTTP status codes here.
+}
+
+// isHTTPStatusRetryable - is HTTP error code retryable.
+func isHTTPStatusRetryable(httpStatusCode int) (ok bool) {
+	_, ok = retryableHTTPStatusCodes[httpStatusCode]
+	return ok
+}