Fix HTTP error handling in remote.Client.Store() (#2708)

Regression introduced in
e5d7bbfc3c

storage/remote/client.go

@@ -122,7 +122,7 @@ func (c *Client) Store(samples model.Samples) error {
 	if httpResp.StatusCode/100 == 5 {
 		return recoverableError{err}
 	}
-	return nil
+	return err
 }
 
 // Name identifies the client.

storage/remote/client_test.go

@@ -0,0 +1,76 @@
+// Copyright 2017 The Prometheus Authors
+// 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 remote
+
+package remote
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/config"
+)
+
+func TestStoreHTTPErrorHandling(t *testing.T) {
+	tests := []struct {
+		code int
+		err  error
+	}{
+		{
+			code: 200,
+			err:  nil,
+		},
+		{
+			code: 300,
+			err:  fmt.Errorf("server returned HTTP status 300 Multiple Choices"),
+		},
+		{
+			code: 404,
+			err:  fmt.Errorf("server returned HTTP status 404 Not Found"),
+		},
+		{
+			code: 500,
+			err:  recoverableError{fmt.Errorf("server returned HTTP status 500 Internal Server Error")},
+		},
+	}
+
+	for i, test := range tests {
+		server := httptest.NewServer(
+			http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				http.Error(w, "test error", test.code)
+			}),
+		)
+
+		serverURL, err := url.Parse(server.URL)
+		if err != nil {
+			panic(err)
+		}
+
+		c, err := NewClient(0, &clientConfig{
+			url:     &config.URL{serverURL},
+			timeout: model.Duration(time.Second),
+		})
+
+		err = c.Store(nil)
+		if !reflect.DeepEqual(err, test.err) {
+			t.Fatalf("%d. Unexpected error; want %v, got %v", i, test.err, err)
+		}
+
+		server.Close()
+	}
+}