notify/discord: Create Discord integration

cmd/alertmanager/main.go

@@ -49,6 +49,7 @@ import (
 	"github.com/prometheus/alertmanager/inhibit"
 	"github.com/prometheus/alertmanager/nflog"
 	"github.com/prometheus/alertmanager/notify"
+	"github.com/prometheus/alertmanager/notify/discord"
 	"github.com/prometheus/alertmanager/notify/email"
 	"github.com/prometheus/alertmanager/notify/opsgenie"
 	"github.com/prometheus/alertmanager/notify/pagerduty"
@@ -173,6 +174,10 @@ func buildReceiverIntegrations(nc *config.Receiver, tmpl *template.Template, log
 	for i, c := range nc.TelegramConfigs {
 		add("telegram", i, c, func(l log.Logger) (notify.Notifier, error) { return telegram.New(c, tmpl, l) })
 	}
+	for i, c := range nc.DiscordConfigs {
+		add("discord", i, c, func(l log.Logger) (notify.Notifier, error) { return discord.New(c, tmpl, l) })
+	}
+
 	if errs.Len() > 0 {
 		return nil, &errs
 	}

config/config.go

@@ -248,6 +248,9 @@ func resolveFilepaths(baseDir string, cfg *Config) {
 		for _, cfg := range receiver.TelegramConfigs {
 			cfg.HTTPConfig.SetDirectory(baseDir)
 		}
+		for _, cfg := range receiver.DiscordConfigs {
+			cfg.HTTPConfig.SetDirectory(baseDir)
+		}
 	}
 }
 
@@ -492,6 +495,14 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 				telegram.APIUrl = c.Global.TelegramAPIUrl
 			}
 		}
+		for _, discord := range rcv.DiscordConfigs {
+			if discord.HTTPConfig == nil {
+				discord.HTTPConfig = c.Global.HTTPConfig
+			}
+			if discord.WebhookURL == nil {
+				return fmt.Errorf("no discord webhook URL provided")
+			}
+		}
 
 		names[rcv.Name] = struct{}{}
 	}
@@ -844,6 +855,7 @@ type Receiver struct {
 	// A unique identifier for this receiver.
 	Name string `yaml:"name" json:"name"`
 
+	DiscordConfigs   []*DiscordConfig   `yaml:"discord_configs,omitempty" json:"discord_configs,omitempty"`
 	EmailConfigs     []*EmailConfig     `yaml:"email_configs,omitempty" json:"email_configs,omitempty"`
 	PagerdutyConfigs []*PagerdutyConfig `yaml:"pagerduty_configs,omitempty" json:"pagerduty_configs,omitempty"`
 	SlackConfigs     []*SlackConfig     `yaml:"slack_configs,omitempty" json:"slack_configs,omitempty"`

config/notifiers.go

@@ -32,6 +32,15 @@ var (
 		},
 	}
 
+	// DefaultDiscordConfig defines default values for Discord configurations.
+	DefaultDiscordConfig = DiscordConfig{
+		NotifierConfig: NotifierConfig{
+			VSendResolved: true,
+		},
+		Title:   `{{ template "discord.default.title" . }}`,
+		Message: `{{ template "discord.default.message" . }}`,
+	}
+
 	// DefaultEmailConfig defines default values for Email configurations.
 	DefaultEmailConfig = EmailConfig{
 		NotifierConfig: NotifierConfig{
@@ -156,6 +165,24 @@ func (nc *NotifierConfig) SendResolved() bool {
 	return nc.VSendResolved
 }
 
+// DiscordConfig configures notifications via Discord.
+type DiscordConfig struct {
+	NotifierConfig `yaml:",inline" json:",inline"`
+
+	HTTPConfig *commoncfg.HTTPClientConfig `yaml:"http_config,omitempty" json:"http_config,omitempty"`
+	WebhookURL *SecretURL                  `yaml:"webhook_url,omitempty" json:"webhook_url,omitempty"`
+
+	Title   string `yaml:"title,omitempty" json:"title,omitempty"`
+	Message string `yaml:"message,omitempty" json:"message,omitempty"`
+}
+
+// UnmarshalYAML implements the yaml.Unmarshaler interface.
+func (c *DiscordConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	*c = DefaultDiscordConfig
+	type plain DiscordConfig
+	return unmarshal((*plain)(c))
+}
+
 // EmailConfig configures notifications via mail.
 type EmailConfig struct {
 	NotifierConfig `yaml:",inline" json:",inline"`

notify/discord/discord.go

@@ -0,0 +1,133 @@
+// Copyright 2021 Prometheus Team
+// 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 discord
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"net/http"
+
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+	commoncfg "github.com/prometheus/common/config"
+	"github.com/prometheus/common/model"
+
+	"github.com/prometheus/alertmanager/config"
+	"github.com/prometheus/alertmanager/notify"
+	"github.com/prometheus/alertmanager/template"
+	"github.com/prometheus/alertmanager/types"
+)
+
+const (
+	colorRed   = 0x992D22
+	colorGreen = 0x2ECC71
+	colorGrey  = 0x95A5A6
+)
+
+// Notifier implements a Notifier for Discord notifications.
+type Notifier struct {
+	conf       *config.DiscordConfig
+	tmpl       *template.Template
+	logger     log.Logger
+	client     *http.Client
+	retrier    *notify.Retrier
+	webhookURL *config.SecretURL
+}
+
+// New returns a new Discord notifier.
+func New(c *config.DiscordConfig, t *template.Template, l log.Logger, httpOpts ...commoncfg.HTTPClientOption) (*Notifier, error) {
+	client, err := commoncfg.NewClientFromConfig(*c.HTTPConfig, "discord", httpOpts...)
+	if err != nil {
+		return nil, err
+	}
+	n := &Notifier{
+		conf:       c,
+		tmpl:       t,
+		logger:     l,
+		client:     client,
+		retrier:    &notify.Retrier{},
+		webhookURL: c.WebhookURL,
+	}
+	return n, nil
+}
+
+type webhook struct {
+	Content string         `json:"content"`
+	Embeds  []webhookEmbed `json:"embeds"`
+}
+
+type webhookEmbed struct {
+	Title       string `json:"title"`
+	Description string `json:"description"`
+	Color       int    `json:"color"`
+}
+
+// Notify implements the Notifier interface.
+func (n *Notifier) Notify(ctx context.Context, as ...*types.Alert) (bool, error) {
+	key, err := notify.ExtractGroupKey(ctx)
+	if err != nil {
+		return false, err
+	}
+
+	level.Debug(n.logger).Log("incident", key)
+
+	alerts := types.Alerts(as...)
+	data := notify.GetTemplateData(ctx, n.tmpl, as, n.logger)
+	tmpl := notify.TmplText(n.tmpl, data, &err)
+	if err != nil {
+		return false, err
+	}
+
+	title := tmpl(n.conf.Title)
+	if err != nil {
+		return false, err
+	}
+	description := tmpl(n.conf.Message)
+	if err != nil {
+		return false, err
+	}
+
+	color := colorGrey
+	if alerts.Status() == model.AlertFiring {
+		color = colorRed
+	}
+	if alerts.Status() == model.AlertResolved {
+		color = colorGreen
+	}
+
+	w := webhook{
+		Embeds: []webhookEmbed{{
+			Title:       title,
+			Description: description,
+			Color:       color,
+		}},
+	}
+
+	var payload bytes.Buffer
+	if err = json.NewEncoder(&payload).Encode(w); err != nil {
+		return false, err
+	}
+
+	resp, err := notify.PostJSON(ctx, n.client, n.webhookURL.String(), &payload)
+	if err != nil {
+		return true, notify.RedactURL(err)
+	}
+
+	shouldRetry, err := n.retrier.Check(resp.StatusCode, resp.Body)
+	if err != nil {
+		return shouldRetry, err
+	}
+	return false, nil
+}

notify/discord/discord_test.go

@@ -0,0 +1,129 @@
+// Copyright 2021 Prometheus Team
+// 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 discord
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/go-kit/log"
+	commoncfg "github.com/prometheus/common/config"
+	"github.com/prometheus/common/model"
+	"github.com/stretchr/testify/require"
+
+	"github.com/prometheus/alertmanager/config"
+	"github.com/prometheus/alertmanager/notify"
+	"github.com/prometheus/alertmanager/notify/test"
+	"github.com/prometheus/alertmanager/types"
+)
+
+// This is a test URL that has been modified to not be valid.
+var testWebhookURL, _ = url.Parse("https://discord.com/api/webhooks/971139602272503183/78ZWZ4V3xwZUBKRFF-G9m1nRtDtNTChl_WzW6Q4kxShjSB02oLSiPTPa8TS2tTGO9EYf")
+
+func TestDiscordRetry(t *testing.T) {
+	notifier, err := New(
+		&config.DiscordConfig{
+			WebhookURL: &config.SecretURL{URL: testWebhookURL},
+			HTTPConfig: &commoncfg.HTTPClientConfig{},
+		},
+		test.CreateTmpl(t),
+		log.NewNopLogger(),
+	)
+	require.NoError(t, err)
+
+	for statusCode, expected := range test.RetryTests(test.DefaultRetryCodes()) {
+		actual, _ := notifier.retrier.Check(statusCode, nil)
+		require.Equal(t, expected, actual, fmt.Sprintf("retry - error on status %d", statusCode))
+	}
+}
+
+func TestDiscordTemplating(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		dec := json.NewDecoder(r.Body)
+		out := make(map[string]interface{})
+		err := dec.Decode(&out)
+		if err != nil {
+			panic(err)
+		}
+	}))
+	defer srv.Close()
+	u, _ := url.Parse(srv.URL)
+
+	for _, tc := range []struct {
+		title string
+		cfg   *config.DiscordConfig
+
+		retry  bool
+		errMsg string
+	}{
+		{
+			title: "full-blown message",
+			cfg: &config.DiscordConfig{
+				Title:   `{{ template "discord.default.title" . }}`,
+				Message: `{{ template "discord.default.message" . }}`,
+			},
+			retry: false,
+		},
+		{
+			title: "title with templating errors",
+			cfg: &config.DiscordConfig{
+				Title: "{{ ",
+			},
+			errMsg: "template: :1: unclosed action",
+		},
+		{
+			title: "message with templating errors",
+			cfg: &config.DiscordConfig{
+				Title:   `{{ template "discord.default.title" . }}`,
+				Message: "{{ ",
+			},
+			errMsg: "template: :1: unclosed action",
+		},
+	} {
+		t.Run(tc.title, func(t *testing.T) {
+			tc.cfg.WebhookURL = &config.SecretURL{URL: u}
+			tc.cfg.HTTPConfig = &commoncfg.HTTPClientConfig{}
+			pd, err := New(tc.cfg, test.CreateTmpl(t), log.NewNopLogger())
+			require.NoError(t, err)
+
+			ctx := context.Background()
+			ctx = notify.WithGroupKey(ctx, "1")
+
+			ok, err := pd.Notify(ctx, []*types.Alert{
+				{
+					Alert: model.Alert{
+						Labels: model.LabelSet{
+							"lbl1": "val1",
+						},
+						StartsAt: time.Now(),
+						EndsAt:   time.Now().Add(time.Hour),
+					},
+				},
+			}...)
+			if tc.errMsg == "" {
+				require.NoError(t, err)
+			} else {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), tc.errMsg)
+			}
+			require.Equal(t, tc.retry, ok)
+		})
+	}
+}

template/default.tmpl

@@ -111,4 +111,16 @@ Alerts Firing:
 Alerts Resolved:
 {{ template "__text_alert_list" .Alerts.Resolved }}
 {{ end }}
-{{ end }}
+{{ end }}
+
+{{ define "discord.default.title" }}{{ template "__subject" . }}{{ end }}
+{{ define "discord.default.message" }}
+{{ if gt (len .Alerts.Firing) 0 }}
+Alerts Firing:
+{{ template "__text_alert_list" .Alerts.Firing }}
+{{ end }}
+{{ if gt (len .Alerts.Resolved) 0 }}
+Alerts Resolved:
+{{ template "__text_alert_list" .Alerts.Resolved }}
+{{ end }}
+{{ end }}