Review feedback: limit number of bytes read under error.

Author: tomwilkie

storage/remote/client.go

@@ -17,6 +17,7 @@ import (
 	"bufio"
 	"bytes"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net/http"
 	"time"
@@ -32,6 +33,8 @@ import (
 	"github.com/prometheus/prometheus/util/httputil"
 )
 
+const maxErrMsgLen = 256
+
 // Client allows reading and writing from/to a remote HTTP endpoint.
 type Client struct {
 	index   int // Used to differentiate metrics.
@@ -118,7 +121,7 @@ func (c *Client) Store(samples model.Samples) error {
 	defer httpResp.Body.Close()
 
 	if httpResp.StatusCode/100 != 2 {
-		scanner := bufio.NewScanner(httpResp.Body)
+		scanner := bufio.NewScanner(io.LimitReader(httpResp.Body, maxErrMsgLen))
 		line := ""
 		if scanner.Scan() {
 			line = scanner.Text()

storage/remote/client_test.go

@@ -19,13 +19,16 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"reflect"
+	"strings"
 	"testing"
 	"time"
 
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/config"
 )
 
+var longErrMessage = strings.Repeat("error message", maxErrMsgLen)
+
 func TestStoreHTTPErrorHandling(t *testing.T) {
 	tests := []struct {
 		code int
@@ -37,22 +40,22 @@ func TestStoreHTTPErrorHandling(t *testing.T) {
 		},
 		{
 			code: 300,
-			err:  fmt.Errorf("server returned HTTP status 300 Multiple Choices: test error"),
+			err:  fmt.Errorf("server returned HTTP status 300 Multiple Choices: " + longErrMessage[:maxErrMsgLen]),
 		},
 		{
 			code: 404,
-			err:  fmt.Errorf("server returned HTTP status 404 Not Found: test error"),
+			err:  fmt.Errorf("server returned HTTP status 404 Not Found: " + longErrMessage[:maxErrMsgLen]),
 		},
 		{
 			code: 500,
-			err:  recoverableError{fmt.Errorf("server returned HTTP status 500 Internal Server Error: test error")},
+			err:  recoverableError{fmt.Errorf("server returned HTTP status 500 Internal Server Error: " + longErrMessage[:maxErrMsgLen])},
 		},
 	}
 
 	for i, test := range tests {
 		server := httptest.NewServer(
 			http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				http.Error(w, "test error", test.code)
+				http.Error(w, longErrMessage, test.code)
 			}),
 		)