Do not log "failed to load config" if runtime config file is empty (#3706)

* Do not log "failed to load config" if runtime config file is empty

Signed-off-by: Marco Pracucci <marco@pracucci.com>

* Do not allow to use a runtime config file containing multiple YAML documents

Signed-off-by: Marco Pracucci <marco@pracucci.com>

* Update pkg/cortex/runtime_config.go

Signed-off-by: Marco Pracucci <marco@pracucci.com>

Co-authored-by: Peter Štibraný <pstibrany@gmail.com>

* Update pkg/cortex/runtime_config.go

Signed-off-by: Marco Pracucci <marco@pracucci.com>

Co-authored-by: Peter Štibraný <pstibrany@gmail.com>

Co-authored-by: Peter Štibraný <pstibrany@gmail.com>

Author: pracucci

CHANGELOG.md

@@ -79,6 +79,8 @@
 * [BUGFIX] Query-Frontend: avoid creating many small sub-queries by discarding cache extents under 5 minutes #3653
 * [BUGFIX] Ruler: Ensure the stale markers generated for evaluated rules respect the configured `-ruler.evaluation-delay-duration`. This will avoid issues with samples with NaN be persisted with timestamps set ahead of the next rule evaluation. #3687
 * [BUGFIX] Alertmanager: don't serve HTTP requests until Alertmanager has fully started. Serving HTTP requests earlier may result in loss of configuration for the user. #3679
+* [BUGFIX] Do not log "failed to load config" if runtime config file is empty. #3706
+* [BUGFIX] Do not allow to use a runtime config file containing multiple YAML documents. #3706
 
 ## 1.6.0
 

pkg/cortex/runtime_config.go

@@ -1,6 +1,7 @@
 package cortex
 
 import (
+	"errors"
 	"io"
 
 	"gopkg.in/yaml.v2"
@@ -10,6 +11,10 @@ import (
 	"github.com/cortexproject/cortex/pkg/util/validation"
 )
 
+var (
+	errMultipleDocuments = errors.New("the provided runtime configuration contains multiple documents")
+)
+
 // runtimeConfigValues are values that can be reloaded from configuration file while Cortex is running.
 // Reloading is done by runtime_config.Manager, which also keeps the currently loaded config.
 // These values are then pushed to the components that are interested in them.
@@ -24,10 +29,17 @@ func loadRuntimeConfig(r io.Reader) (interface{}, error) {
 
 	decoder := yaml.NewDecoder(r)
 	decoder.SetStrict(true)
-	if err := decoder.Decode(&overrides); err != nil {
+
+	// Decode the first document. An empty document (EOF) is OK.
+	if err := decoder.Decode(&overrides); err != nil && !errors.Is(err, io.EOF) {
 		return nil, err
 	}
 
+	// Ensure the provided YAML config is not composed of multiple documents,
+	if err := decoder.Decode(&runtimeConfigValues{}); !errors.Is(err, io.EOF) {
+		return nil, errMultipleDocuments
+	}
+
 	return overrides, nil
 }
 

pkg/cortex/runtime_config_test.go

@@ -4,6 +4,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/cortexproject/cortex/pkg/util/validation"
@@ -12,7 +13,7 @@ import (
 // Given limits are usually loaded via a config file, and that
 // a configmap is limited to 1MB, we need to minimise the limits file.
 // One way to do it is via YAML anchors.
-func TestLoadingAnchoredRuntimeYAML(t *testing.T) {
+func TestLoadRuntimeConfig_ShouldLoadAnchoredYAML(t *testing.T) {
 	yamlFile := strings.NewReader(`
 overrides:
   '1234': &id001
@@ -49,3 +50,50 @@ overrides:
 	require.Equal(t, limits, *loadedLimits["1235"])
 	require.Equal(t, limits, *loadedLimits["1236"])
 }
+
+func TestLoadRuntimeConfig_ShouldLoadEmptyFile(t *testing.T) {
+	yamlFile := strings.NewReader(`
+# This is an empty YAML.
+`)
+	actual, err := loadRuntimeConfig(yamlFile)
+	require.NoError(t, err)
+	assert.Equal(t, &runtimeConfigValues{}, actual)
+}
+
+func TestLoadRuntimeConfig_ShouldReturnErrorOnMultipleDocumentsInTheConfig(t *testing.T) {
+	cases := []string{
+		`
+---
+---
+`, `
+---
+overrides:
+  '1234':
+    ingestion_burst_size: 123
+---
+overrides:
+  '1234':
+    ingestion_burst_size: 123
+`, `
+---
+# This is an empty YAML.
+---
+overrides:
+  '1234':
+    ingestion_burst_size: 123
+`, `
+---
+overrides:
+  '1234':
+    ingestion_burst_size: 123
+---
+# This is an empty YAML.
+`,
+	}
+
+	for _, tc := range cases {
+		actual, err := loadRuntimeConfig(strings.NewReader(tc))
+		assert.Equal(t, errMultipleDocuments, err)
+		assert.Nil(t, actual)
+	}
+}

pkg/util/runtimeconfig/manager.go

@@ -146,14 +146,14 @@ func (om *Manager) loadConfig() error {
 	buf, err := ioutil.ReadFile(om.cfg.LoadPath)
 	if err != nil {
 		om.configLoadSuccess.Set(0)
-		return err
+		return errors.Wrap(err, "read file")
 	}
 	hash := sha256.Sum256(buf)
 
 	cfg, err := om.cfg.Loader(bytes.NewReader(buf))
 	if err != nil {
 		om.configLoadSuccess.Set(0)
-		return err
+		return errors.Wrap(err, "load file")
 	}
 	om.configLoadSuccess.Set(1)