Add support to set the Slack URL in a file

- Added support for the file in both the global and the lower level
- Tried to follow configuration patterns I saw in prometheus
- The slack file is read on every request as mentioned in the prometheus issue to enable seamless switches

prometheus#2498

config/config.go

@@ -301,6 +301,10 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		*c.Global = DefaultGlobalConfig()
 	}
 
+	if c.Global.SlackAPIURL != nil && len(c.Global.SlackAPIURLFile) > 0 {
+		return fmt.Errorf("at most one of slack_api_url & slack_api_url_file must be configured")
+	}
+
 	names := map[string]struct{}{}
 
 	for _, rcv := range c.Receivers {
@@ -349,11 +353,12 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 			if sc.HTTPConfig == nil {
 				sc.HTTPConfig = c.Global.HTTPConfig
 			}
-			if sc.APIURL == nil {
-				if c.Global.SlackAPIURL == nil {
-					return fmt.Errorf("no global Slack API URL set")
+			if sc.APIURL == nil && len(sc.APIURLFile) == 0 {
+				if c.Global.SlackAPIURL == nil && len(c.Global.SlackAPIURLFile) == 0 {
+					return fmt.Errorf("no global Slack API URL set either inline or in a file")
 				}
 				sc.APIURL = c.Global.SlackAPIURL
+				sc.APIURLFile = c.Global.SlackAPIURLFile
 			}
 		}
 		for _, poc := range rcv.PushoverConfigs {
@@ -632,6 +637,7 @@ type GlobalConfig struct {
 	SMTPAuthIdentity string     `yaml:"smtp_auth_identity,omitempty" json:"smtp_auth_identity,omitempty"`
 	SMTPRequireTLS   bool       `yaml:"smtp_require_tls" json:"smtp_require_tls,omitempty"`
 	SlackAPIURL      *SecretURL `yaml:"slack_api_url,omitempty" json:"slack_api_url,omitempty"`
+	SlackAPIURLFile  string     `yaml:"slack_api_url_file,omitempty" json:"slack_api_url_file,omitempty"`
 	PagerdutyURL     *URL       `yaml:"pagerduty_url,omitempty" json:"pagerduty_url,omitempty"`
 	OpsGenieAPIURL   *URL       `yaml:"opsgenie_api_url,omitempty" json:"opsgenie_api_url,omitempty"`
 	OpsGenieAPIKey   Secret     `yaml:"opsgenie_api_key,omitempty" json:"opsgenie_api_key,omitempty"`

config/config_test.go

@@ -859,6 +859,51 @@ func TestOpsGenieDeprecatedTeamSpecified(t *testing.T) {
 	}
 }
 
+func TestSlackBothAPIURLAndFile(t *testing.T) {
+	_, err := LoadFile("testdata/conf.slack-both-file-and-url.yml")
+	if err == nil {
+		t.Fatalf("Expected an error parsing %s: %s", "testdata/conf.slack-both-file-and-url.yml", err)
+	}
+	if err.Error() != "at most one of slack_api_url & slack_api_url_file must be configured" {
+		t.Errorf("Expected: %s\nGot: %s", "at most one of slack_api_url & slack_api_url_file must be configured", err.Error())
+	}
+}
+
+func TestSlackNoAPIURL(t *testing.T) {
+	_, err := LoadFile("testdata/conf.slack-no-api-url.yml")
+	if err == nil {
+		t.Fatalf("Expected an error parsing %s: %s", "testdata/conf.slack-no-api-url.yml", err)
+	}
+	if err.Error() != "no global Slack API URL set either inline or in a file" {
+		t.Errorf("Expected: %s\nGot: %s", "no global Slack API URL set either inline or in a file", err.Error())
+	}
+}
+
+func TestSlackGlobalAPIURLFile(t *testing.T) {
+	conf, err := LoadFile("testdata/conf.slack-default-api-url-file.yml")
+	if err != nil {
+		t.Fatalf("Error parsing %s: %s", "testdata/conf.slack-default-api-url-file.yml", err)
+	}
+
+	// no override
+	firstConfig := conf.Receivers[0].SlackConfigs[0]
+	if firstConfig.APIURLFile != "/global_file" || firstConfig.APIURL != nil {
+		t.Fatalf("Invalid Slack URL file: %s\nExpected: %s", firstConfig.APIURLFile, "/global_file")
+	}
+
+	// override the file
+	secondConfig := conf.Receivers[0].SlackConfigs[1]
+	if secondConfig.APIURLFile != "/override_file" || secondConfig.APIURL != nil {
+		t.Fatalf("Invalid Slack URL file: %s\nExpected: %s", secondConfig.APIURLFile, "/override_file")
+	}
+
+	// override the global file with an inline URL
+	thirdConfig := conf.Receivers[0].SlackConfigs[2]
+	if thirdConfig.APIURL.String() != "http://mysecret.example.com/" || thirdConfig.APIURLFile != "" {
+		t.Fatalf("Invalid Slack URL: %s\nExpected: %s", thirdConfig.APIURL.String(), "http://mysecret.example.com/")
+	}
+}
+
 func TestUnmarshalHostPort(t *testing.T) {
 	for _, tc := range []struct {
 		in string

config/notifiers.go

@@ -328,7 +328,8 @@ type SlackConfig struct {
 
 	HTTPConfig *commoncfg.HTTPClientConfig `yaml:"http_config,omitempty" json:"http_config,omitempty"`
 
-	APIURL *SecretURL `yaml:"api_url,omitempty" json:"api_url,omitempty"`
+	APIURL     *SecretURL `yaml:"api_url,omitempty" json:"api_url,omitempty"`
+	APIURLFile string     `yaml:"api_url_file,omitempty" json:"api_url_file,omitempty"`
 
 	// Slack channel override, (like #other-channel or @username).
 	Channel  string `yaml:"channel,omitempty" json:"channel,omitempty"`
@@ -357,7 +358,15 @@ type SlackConfig struct {
 func (c *SlackConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	*c = DefaultSlackConfig
 	type plain SlackConfig
-	return unmarshal((*plain)(c))
+	if err := unmarshal((*plain)(c)); err != nil {
+		return err
+	}
+
+	if c.APIURL != nil && len(c.APIURLFile) > 0 {
+		return fmt.Errorf("at most one of api_url & api_url_file must be configured")
+	}
+
+	return nil
 }
 
 // WebhookConfig configures notifications via a generic webhook.
@@ -490,7 +499,8 @@ type VictorOpsConfig struct {
 
 	HTTPConfig *commoncfg.HTTPClientConfig `yaml:"http_config,omitempty" json:"http_config,omitempty"`
 
-	APIKey            Secret            `yaml:"api_key" json:"api_key"`
+	APIKey            Secret            `yaml:"api_key,omitempty" json:"api_key,omitempty"`
+	APIKeyFile        Secret            `yaml:"api_key_file,omitempty" json:"api_key_file,omitempty"`
 	APIURL            *URL              `yaml:"api_url" json:"api_url"`
 	RoutingKey        string            `yaml:"routing_key" json:"routing_key"`
 	MessageType       string            `yaml:"message_type" json:"message_type"`

config/testdata/conf.slack-both-file-and-url.yml

@@ -0,0 +1,14 @@
+global:
+  slack_api_url: "http://mysecret.example.com/"
+  slack_api_url_file: '/global_file'
+
+route:
+  receiver: 'slack-notifications'
+  group_by: [alertname, datacenter, app]
+
+receivers:
+- name: 'slack-notifications'
+  slack_configs:
+  - channel: '#alerts1'
+    text: 'test'
+

config/testdata/conf.slack-default-api-url-file.yml

@@ -0,0 +1,22 @@
+global:
+  slack_api_url_file: '/global_file'
+
+route:
+  receiver: 'slack-notifications'
+  group_by: [alertname, datacenter, app]
+
+receivers:
+- name: 'slack-notifications'
+  slack_configs:
+  # Use global
+  - channel: '#alerts1'
+    text: 'test'
+  # Override global with other file
+  - channel: '#alerts2'
+    text: 'test'
+    api_url_file: '/override_file'
+  # Override global with inline URL
+  - channel: '#alerts3'
+    text: 'test'
+    api_url: 'http://mysecret.example.com/'
+

config/testdata/conf.slack-no-api-url.yml

@@ -0,0 +1,9 @@
+route:
+  receiver: 'slack-notifications'
+  group_by: [alertname, datacenter, app]
+
+receivers:
+- name: 'slack-notifications'
+  slack_configs:
+  - channel: '#alerts'
+    text: 'test'

notify/slack/slack.go

@@ -18,9 +18,11 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"github.com/pkg/errors"
+	"io/ioutil"
 	"net/http"
 
+	"github.com/pkg/errors"
+
 	"github.com/go-kit/kit/log"
 	commoncfg "github.com/prometheus/common/config"
 
@@ -175,7 +177,17 @@ func (n *Notifier) Notify(ctx context.Context, as ...*types.Alert) (bool, error)
 		return false, err
 	}
 
-	u := n.conf.APIURL.String()
+	var u string
+	if n.conf.APIURL != nil {
+		u = n.conf.APIURL.String()
+	} else {
+		content, err := ioutil.ReadFile(n.conf.APIURLFile)
+		if err != nil {
+			return false, err
+		}
+		u = string(content)
+	}
+
 	resp, err := notify.PostJSON(ctx, n.client, u, &buf)
 	if err != nil {
 		return true, notify.RedactURL(err)

notify/slack/slack_test.go

@@ -15,6 +15,7 @@ package slack
 
 import (
 	"fmt"
+	"io/ioutil"
 	"testing"
 
 	"github.com/go-kit/kit/log"
@@ -57,3 +58,25 @@ func TestSlackRedactedURL(t *testing.T) {
 
 	test.AssertNotifyLeaksNoSecret(t, ctx, notifier, u.String())
 }
+
+func TestGettingSlackURLFromFile(t *testing.T) {
+	ctx, u, fn := test.GetContextWithCancelingURL()
+	defer fn()
+
+	f, err := ioutil.TempFile("", "slack_test")
+	require.NoError(t, err, "creating temp file failed")
+	_, err = f.WriteString(u.String())
+	require.NoError(t, err, "writing to temp file failed")
+
+	notifier, err := New(
+		&config.SlackConfig{
+			APIURLFile: f.Name(),
+			HTTPConfig: &commoncfg.HTTPClientConfig{},
+		},
+		test.CreateTmpl(t),
+		log.NewNopLogger(),
+	)
+	require.NoError(t, err)
+
+	test.AssertNotifyLeaksNoSecret(t, ctx, notifier, u.String())
+}