Merge pull request kubernetes#75368 from mfojtik/retry-on-errors

rest: retry on connection refused and apiserver shutdown

Author: k8s-ci-robot

staging/src/k8s.io/apiserver/pkg/server/filters/BUILD

@@ -43,7 +43,9 @@ go_library(
     importmap = "k8s.io/kubernetes/vendor/k8s.io/apiserver/pkg/server/filters",
     importpath = "k8s.io/apiserver/pkg/server/filters",
     deps = [
+        "//staging/src/k8s.io/api/core/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/api/errors:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/wait:go_default_library",
@@ -53,6 +55,7 @@ go_library(
         "//staging/src/k8s.io/apiserver/pkg/endpoints/metrics:go_default_library",
         "//staging/src/k8s.io/apiserver/pkg/endpoints/request:go_default_library",
         "//staging/src/k8s.io/apiserver/pkg/server/httplog:go_default_library",
+        "//staging/src/k8s.io/client-go/kubernetes/scheme:go_default_library",
         "//vendor/k8s.io/klog:go_default_library",
     ],
 )

staging/src/k8s.io/apiserver/pkg/server/filters/waitgroup.go

@@ -18,11 +18,16 @@ package filters
 
 import (
 	"errors"
+	"fmt"
 	"net/http"
 
+	"k8s.io/api/core/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/runtime"
 	utilwaitgroup "k8s.io/apimachinery/pkg/util/waitgroup"
 	"k8s.io/apiserver/pkg/endpoints/handlers/responsewriters"
 	apirequest "k8s.io/apiserver/pkg/endpoints/request"
+	"k8s.io/client-go/kubernetes/scheme"
 )
 
 // WithWaitGroup adds all non long-running requests to wait group, which is used for graceful shutdown.
@@ -38,7 +43,14 @@ func WithWaitGroup(handler http.Handler, longRunning apirequest.LongRunningReque
 
 		if !longRunning(req, requestInfo) {
 			if err := wg.Add(1); err != nil {
-				http.Error(w, "apiserver is shutting down.", http.StatusInternalServerError)
+				// When apiserver is shutting down, signal clients to retry
+				// There is a good chance the client hit a different server, so a tight retry is good for client responsiveness.
+				w.Header().Add("Retry-After", "1")
+				w.Header().Set("Content-Type", runtime.ContentTypeJSON)
+				w.Header().Set("X-Content-Type-Options", "nosniff")
+				statusErr := apierrors.NewServiceUnavailable("apiserver is shutting down").Status()
+				w.WriteHeader(int(statusErr.Code))
+				fmt.Fprintln(w, runtime.EncodeOrDie(scheme.Codecs.LegacyCodec(v1.SchemeGroupVersion), &statusErr))
 				return
 			}
 			defer wg.Done()

staging/src/k8s.io/client-go/rest/request.go

@@ -806,19 +806,24 @@ func (r *Request) request(fn func(*http.Request, *http.Response)) error {
 			r.backoff.UpdateBackoff(r.URL(), err, resp.StatusCode)
 		}
 		if err != nil {
-			// "Connection reset by peer" is usually a transient error.
+			// "Connection reset by peer", "Connection refused" or "apiserver is shutting down" are usually a transient errors.
 			// Thus in case of "GET" operations, we simply retry it.
 			// We are not automatically retrying "write" operations, as
 			// they are not idempotent.
-			if !net.IsConnectionReset(err) || r.verb != "GET" {
+			if r.verb != "GET" {
 				return err
 			}
-			// For the purpose of retry, we set the artificial "retry-after" response.
-			// TODO: Should we clean the original response if it exists?
-			resp = &http.Response{
-				StatusCode: http.StatusInternalServerError,
-				Header:     http.Header{"Retry-After": []string{"1"}},
-				Body:       ioutil.NopCloser(bytes.NewReader([]byte{})),
+			// For connection errors and apiserver shutdown errors retry.
+			if net.IsConnectionReset(err) || net.IsConnectionRefused(err) {
+				// For the purpose of retry, we set the artificial "retry-after" response.
+				// TODO: Should we clean the original response if it exists?
+				resp = &http.Response{
+					StatusCode: http.StatusInternalServerError,
+					Header:     http.Header{"Retry-After": []string{"1"}},
+					Body:       ioutil.NopCloser(bytes.NewReader([]byte{})),
+				}
+			} else {
+				return err
 			}
 		}