config: Change DefaultGlobalConfig to a function (#1656)

The variable DefaultGlobalConfig was being used to initialize values, but it stored previous information due to which some things were persisting in the newer initialization.

In this PR, DefaultGlobalConfig is changed to a function so that it returns a fresh GlobalConfig for initialization.

Signed-off-by: Hrishikesh Barman <hrishikeshbman@gmail.com>

config/config.go

@@ -44,7 +44,7 @@ func init() {
 // Secret is a string that must not be revealed on marshaling.
 type Secret string
 
-// MarshalYAML implements the yaml.Marshaler interface.
+// MarshalYAML implements the yaml.Marshaler interface for Secret.
 func (s Secret) MarshalYAML() (interface{}, error) {
 	if s != "" {
 		return secretToken, nil
@@ -58,7 +58,7 @@ func (s *Secret) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	return unmarshal((*plain)(s))
 }
 
-// MarshalJSON implements the json.Marshaler interface.
+// MarshalJSON implements the json.Marshaler interface for Secret.
 func (s Secret) MarshalJSON() ([]byte, error) {
 	return json.Marshal(secretToken)
 }
@@ -235,7 +235,7 @@ func (c Config) String() string {
 	return string(b)
 }
 
-// UnmarshalYAML implements the yaml.Unmarshaler interface.
+// UnmarshalYAML implements the yaml.Unmarshaler interface for Config.
 func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	// We want to set c to the defaults and then overwrite it with the input.
 	// To make unmarshal fill the plain data struct rather than calling UnmarshalYAML
@@ -249,7 +249,7 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	// We have to restore it here.
 	if c.Global == nil {
 		c.Global = &GlobalConfig{}
-		*c.Global = DefaultGlobalConfig
+		*c.Global = DefaultGlobalConfig()
 	}
 
 	names := map[string]struct{}{}
@@ -449,18 +449,20 @@ func checkReceiver(r *Route, receivers map[string]struct{}) error {
 	return nil
 }
 
-// DefaultGlobalConfig provides global default values.
-var DefaultGlobalConfig = GlobalConfig{
-	ResolveTimeout: model.Duration(5 * time.Minute),
-	HTTPConfig:     &commoncfg.HTTPClientConfig{},
+// DefaultGlobalConfig returns GlobalConfig with default values.
+func DefaultGlobalConfig() GlobalConfig {
+	return GlobalConfig{
+		ResolveTimeout: model.Duration(5 * time.Minute),
+		HTTPConfig:     &commoncfg.HTTPClientConfig{},
 
-	SMTPHello:       "localhost",
-	SMTPRequireTLS:  true,
-	PagerdutyURL:    mustParseURL("https://events.pagerduty.com/v2/enqueue"),
-	HipchatAPIURL:   mustParseURL("https://api.hipchat.com/"),
-	OpsGenieAPIURL:  mustParseURL("https://api.opsgenie.com/"),
-	WeChatAPIURL:    mustParseURL("https://qyapi.weixin.qq.com/cgi-bin/"),
-	VictorOpsAPIURL: mustParseURL("https://alert.victorops.com/integrations/generic/20131114/alert/"),
+		SMTPHello:       "localhost",
+		SMTPRequireTLS:  true,
+		PagerdutyURL:    mustParseURL("https://events.pagerduty.com/v2/enqueue"),
+		HipchatAPIURL:   mustParseURL("https://api.hipchat.com/"),
+		OpsGenieAPIURL:  mustParseURL("https://api.opsgenie.com/"),
+		WeChatAPIURL:    mustParseURL("https://qyapi.weixin.qq.com/cgi-bin/"),
+		VictorOpsAPIURL: mustParseURL("https://alert.victorops.com/integrations/generic/20131114/alert/"),
+	}
 }
 
 func mustParseURL(s string) *URL {
@@ -515,9 +517,9 @@ type GlobalConfig struct {
 	VictorOpsAPIKey  Secret     `yaml:"victorops_api_key,omitempty" json:"victorops_api_key,omitempty"`
 }
 
-// UnmarshalYAML implements the yaml.Unmarshaler interface.
+// UnmarshalYAML implements the yaml.Unmarshaler interface for GlobalConfig.
 func (c *GlobalConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
-	*c = DefaultGlobalConfig
+	*c = DefaultGlobalConfig()
 	type plain GlobalConfig
 	return unmarshal((*plain)(c))
 }
@@ -540,7 +542,7 @@ type Route struct {
 	RepeatInterval *model.Duration `yaml:"repeat_interval,omitempty" json:"repeat_interval,omitempty"`
 }
 
-// UnmarshalYAML implements the yaml.Unmarshaler interface.
+// UnmarshalYAML implements the yaml.Unmarshaler interface for Route.
 func (r *Route) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type plain Route
 	if err := unmarshal((*plain)(r)); err != nil {
@@ -614,7 +616,7 @@ type InhibitRule struct {
 	Equal model.LabelNames `yaml:"equal,omitempty" json:"equal,omitempty"`
 }
 
-// UnmarshalYAML implements the yaml.Unmarshaler interface.
+// UnmarshalYAML implements the yaml.Unmarshaler interface for InhibitRule.
 func (r *InhibitRule) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type plain InhibitRule
 	if err := unmarshal((*plain)(r)); err != nil {
@@ -664,7 +666,7 @@ type Receiver struct {
 	VictorOpsConfigs []*VictorOpsConfig `yaml:"victorops_configs,omitempty" json:"victorops_configs,omitempty"`
 }
 
-// UnmarshalYAML implements the yaml.Unmarshaler interface.
+// UnmarshalYAML implements the yaml.Unmarshaler interface for Receiver.
 func (c *Receiver) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type plain Receiver
 	if err := unmarshal((*plain)(c)); err != nil {
@@ -681,7 +683,7 @@ type Regexp struct {
 	*regexp.Regexp
 }
 
-// UnmarshalYAML implements the yaml.Unmarshaler interface.
+// UnmarshalYAML implements the yaml.Unmarshaler interface for Regexp.
 func (re *Regexp) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	var s string
 	if err := unmarshal(&s); err != nil {
@@ -695,7 +697,7 @@ func (re *Regexp) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	return nil
 }
 
-// MarshalYAML implements the yaml.Marshaler interface.
+// MarshalYAML implements the yaml.Marshaler interface for Regexp.
 func (re Regexp) MarshalYAML() (interface{}, error) {
 	if re.Regexp != nil {
 		return re.String(), nil
@@ -703,7 +705,7 @@ func (re Regexp) MarshalYAML() (interface{}, error) {
 	return nil, nil
 }
 
-// UnmarshalJSON implements the json.Marshaler interface
+// UnmarshalJSON implements the json.Marshaler interface for Regexp
 func (re *Regexp) UnmarshalJSON(data []byte) error {
 	var s string
 	if err := json.Unmarshal(data, &s); err != nil {
@@ -717,7 +719,7 @@ func (re *Regexp) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
-// MarshalJSON implements the json.Marshaler interface.
+// MarshalJSON implements the json.Marshaler interface for Regexp.
 func (re Regexp) MarshalJSON() ([]byte, error) {
 	if re.Regexp != nil {
 		return json.Marshal(re.String())

config/config_test.go

@@ -573,6 +573,13 @@ func TestEmptyFieldsAndRegex(t *testing.T) {
 		},
 	}
 
+	// Load a non-empty configuration to ensure that all fields are overwritten.
+	// See https://github.com/prometheus/alertmanager/issues/1649.
+	_, _, err := LoadFile("testdata/conf.good.yml")
+	if err != nil {
+		t.Errorf("Error parsing %s: %s", "testdata/conf.good.yml", err)
+	}
+
 	config, _, err := LoadFile("testdata/conf.empty-fields.yml")
 	if err != nil {
 		t.Errorf("Error parsing %s: %s", "testdata/conf.empty-fields.yml", err)

config/testdata/conf.good.yml

@@ -10,6 +10,8 @@ global:
   # Alternative host for Hipchat.
   hipchat_api_url: 'https://hipchat.foobar.org/'
   slack_api_url: "http://mysecret.example.com/"
+  http_config:
+    proxy_url: 'http://127.0.0.1:1025'