fix: drain the req.body into io.Discard correctly (#17881)

internal/event/target/elasticsearch.go

@@ -23,7 +23,6 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
-	"io"
 	"net/http"
 	"net/url"
 	"os"
@@ -475,12 +474,10 @@ func (c *esClientV7) createIndex(args ElasticsearchArgs) error {
 		if err != nil {
 			return err
 		}
-		defer resp.Body.Close()
+		defer DrainBody(resp.Body)
 		if resp.IsError() {
-			err := fmt.Errorf("Create index err: %s", res.String())
-			return err
+			return fmt.Errorf("Create index err: %v", res)
 		}
-		io.Copy(io.Discard, resp.Body)
 		return nil
 	}
 	return nil
@@ -493,8 +490,7 @@ func (c *esClientV7) ping(ctx context.Context, _ ElasticsearchArgs) (bool, error
 	if err != nil {
 		return false, store.ErrNotConnected
 	}
-	io.Copy(io.Discard, resp.Body)
-	resp.Body.Close()
+	DrainBody(resp.Body)
 	return !resp.IsError(), nil
 }
 
@@ -507,8 +503,7 @@ func (c *esClientV7) entryExists(ctx context.Context, index string, key string)
 	if err != nil {
 		return false, err
 	}
-	io.Copy(io.Discard, res.Body)
-	res.Body.Close()
+	DrainBody(res.Body)
 	return !res.IsError(), nil
 }
 
@@ -523,8 +518,7 @@ func (c *esClientV7) removeEntry(ctx context.Context, index string, key string)
 		if err != nil {
 			return err
 		}
-		defer res.Body.Close()
-		defer io.Copy(io.Discard, res.Body)
+		defer DrainBody(res.Body)
 		if res.IsError() {
 			return fmt.Errorf("Delete err: %s", res.String())
 		}
@@ -552,8 +546,7 @@ func (c *esClientV7) updateEntry(ctx context.Context, index string, key string,
 	if err != nil {
 		return err
 	}
-	defer res.Body.Close()
-	defer io.Copy(io.Discard, res.Body)
+	defer DrainBody(res.Body)
 	if res.IsError() {
 		return fmt.Errorf("Update err: %s", res.String())
 	}
@@ -579,8 +572,7 @@ func (c *esClientV7) addEntry(ctx context.Context, index string, eventData event
 	if err != nil {
 		return err
 	}
-	defer res.Body.Close()
-	defer io.Copy(io.Discard, res.Body)
+	defer DrainBody(res.Body)
 	if res.IsError() {
 		return fmt.Errorf("Add err: %s", res.String())
 	}

internal/event/target/webhook.go

@@ -34,6 +34,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/dustin/go-humanize"
 	"github.com/minio/minio/internal/event"
 	"github.com/minio/minio/internal/logger"
 	"github.com/minio/minio/internal/once"
@@ -194,8 +195,7 @@ func (target *WebhookTarget) send(eventData event.Event) error {
 	if err != nil {
 		return err
 	}
-	defer resp.Body.Close()
-	io.Copy(io.Discard, resp.Body)
+	defer DrainBody(resp.Body)
 
 	if resp.StatusCode < 200 || resp.StatusCode > 299 {
 		return fmt.Errorf("sending event failed with %v", resp.Status)
@@ -297,3 +297,23 @@ func NewWebhookTarget(ctx context.Context, id string, args WebhookArgs, loggerOn
 
 	return target, nil
 }
+
+// DrainBody close non nil response with any response Body.
+// convenient wrapper to drain any remaining data on response body.
+//
+// Subsequently this allows golang http RoundTripper
+// to re-use the same connection for future requests.
+func DrainBody(respBody io.ReadCloser) {
+	// Callers should close resp.Body when done reading from it.
+	// If resp.Body is not closed, the Client's underlying RoundTripper
+	// (typically Transport) may not be able to re-use a persistent TCP
+	// connection to the server for a subsequent "keep-alive" request.
+	if respBody != nil {
+		// Drain any remaining Body and then close the connection.
+		// Without this closing connection would disallow re-using
+		// the same connection for future uses.
+		//  - http://stackoverflow.com/a/17961593/4465767
+		defer respBody.Close()
+		io.CopyN(io.Discard, respBody, 1*humanize.MiByte)
+	}
+}