config: prevent overwrite of DefaultGlobalConfig

config/config.go

@@ -46,7 +46,7 @@ func LoadFromFile(filename string) (*Config, error) {
 var (
 	// The default top-level configuration.
 	DefaultConfig = Config{
-		GlobalConfig: &DefaultGlobalConfig,
+		GlobalConfig: DefaultGlobalConfig,
 	}
 
 	// The default global configuration.
@@ -56,7 +56,7 @@ var (
 		EvaluationInterval: Duration(1 * time.Minute),
 	}
 
-	// Te default scrape configuration.
+	// The default scrape configuration.
 	DefaultScrapeConfig = ScrapeConfig{
 		// ScrapeTimeout and ScrapeInterval default to the
 		// configured globals.
@@ -89,7 +89,7 @@ var (
 
 // Config is the top-level configuration for Prometheus's config files.
 type Config struct {
-	GlobalConfig  *GlobalConfig   `yaml:"global"`
+	GlobalConfig  GlobalConfig    `yaml:"global"`
 	RuleFiles     []string        `yaml:"rule_files,omitempty"`
 	ScrapeConfigs []*ScrapeConfig `yaml:"scrape_configs,omitempty"`
 

config/config_test.go

@@ -13,7 +13,7 @@ import (
 )
 
 var expectedConf = &Config{
-	GlobalConfig: &GlobalConfig{
+	GlobalConfig: GlobalConfig{
 		ScrapeInterval:     Duration(15 * time.Second),
 		ScrapeTimeout:      DefaultGlobalConfig.ScrapeTimeout,
 		EvaluationInterval: Duration(30 * time.Second),
@@ -118,6 +118,12 @@ var expectedConf = &Config{
 }
 
 func TestLoadConfig(t *testing.T) {
+	// Parse a valid file that sets a global scrape timeout. This tests whether parsing
+	// an overwritten default field in the global config permanently changes the default.
+	if _, err := LoadFromFile("testdata/global_timeout.good.yml"); err != nil {
+		t.Errorf("Error parsing %s: %s", "testdata/conf.good.yml", err)
+	}
+
 	c, err := LoadFromFile("testdata/conf.good.yml")
 	if err != nil {
 		t.Errorf("Error parsing %s: %s", "testdata/conf.good.yml", err)

config/testdata/global_timeout.good.yml

@@ -0,0 +1,2 @@
+global:
+  scrape_timeout: 1h