Initial Prometheus alertmanager webhook

README.md

 with the `default_channel` setting, significantly reduces configuration effort compared to
 GitHub's old integrations system.
 
+### Prometheus Alertmanager Webhook
+```json
+"prometheus": "#channel"
+```
+
+Receives [Prometheus Alertmanager webhooks](https://prometheus.io/docs/alerting/configuration/#webhook_config) at `/prometheus`. They will be sent to the channel defined in `http.listeners.prometheus`. Note that this endpoint is unauthenticated.
+
 ## IRC → Shell
 You can use irccat to execute commands from IRC:
 

go.mod

 	github.com/deckarep/golang-set v1.7.1
 	github.com/fsnotify/fsnotify v1.4.7
 	github.com/juju/loggo v0.0.0-20190526231331-6e530bcce5d8
+	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/spf13/viper v1.5.0
+	github.com/stretchr/testify v1.3.0 // indirect
 	github.com/thoj/go-ircevent v0.0.0-20190807115034-8e7ce4b5a1eb
+	golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e // indirect
 	gopkg.in/go-playground/webhooks.v5 v5.13.0
+	gopkg.in/yaml.v2 v2.2.7 // indirect
 )

go.sum

 github.com/coreos/go-semver v0.2.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
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 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/deckarep/golang-set v1.7.1 h1:SCQV0S6gTtp6itiFrTqI+pfmJ4LN85S1YzhDf9rTHJQ=
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 github.com/soheilhy/cmux v0.1.4/go.mod h1:IM3LyeVVIOuxMH7sFAkER9+bJ4dT7Ms6E4xg4kGIyLM=
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 github.com/spf13/jwalterweatherman v1.0.0/go.mod h1:cQK4TGJAtQXfYWX+Ddv3mKDzgVb68N+wFjFa4jdeBTo=
 github.com/spf13/pflag v1.0.3 h1:zPAT6CGy6wXeQ7NtTnaTerfKOsV6V6F8agHXFiazDkg=
 github.com/spf13/pflag v1.0.3/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
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+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
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 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2 h1:VklqNMn3ovrHsnt90PveolxSbWFaJdECFbxSq0Mqo2M=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
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 golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a h1:1BGLXjeY4akVXGgbC9HugT3Jv3hCI0z56oJR5vAMgBU=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
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 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

httplistener/httplistener.go

 		mux.HandleFunc("/github", hl.githubHandler)
 	}
 
+	if viper.IsSet("http.listeners.prometheus") {
+		log.Infof("Listening for Prometheus Alertmanager webhooks at /prometheus")
+		mux.HandleFunc("/prometheus", hl.prometheusHandler)
+	}
+
 	hl.http.Handler = mux
 	if viper.GetBool("http.tls") {
 		go hl.http.ListenAndServeTLS(viper.GetString("http.tls_cert"), viper.GetString("http.tls_key"))

httplistener/prometheus.go

+package httplistener
+
+import (
+	"bytes"
+	"encoding/json"
+	"github.com/spf13/viper"
+	"net/http"
+)
+
+type HookMessage struct {
+	Version           string            `json:"version"`
+	GroupKey          string            `json:"groupKey"`
+	Status            string            `json:"status"`
+	Receiver          string            `json:"receiver"`
+	GroupLabels       map[string]string `json:"groupLabels"`
+	CommonLabels      map[string]string `json:"commonLabels"`
+	CommonAnnotations map[string]string `json:"commonAnnotations"`
+	ExternalURL       string            `json:"externalURL"`
+	Alerts            []Alert           `json:"alerts"`
+}
+
+type Alert struct {
+	Status       string            `json:"status"`
+	Labels       map[string]string `json:"labels"`
+	Annotations  map[string]string `json:"annotations"`
+	StartsAt     string            `json:"startsAt,omitempty"`
+	EndsAt       string            `json:"endsAt,omitempty"`
+	GeneratorURL string            `json:"generatorURL"`
+}
+
+func (hl *HTTPListener) prometheusHandler(w http.ResponseWriter, request *http.Request) {
+	if request.Method != "POST" {
+		http.NotFound(w, request)
+		return
+	}
+
+	var message HookMessage
+	buf := new(bytes.Buffer)
+	buf.ReadFrom(request.Body)
+	json.Unmarshal(buf.Bytes(), &message)
+	log.Infof("%s [%s] Prometheus alert", request.RemoteAddr, viper.GetString("http.listeners.prometheus"))
+
+	msgs, err := hl.renderTemplate("prometheus.alert", message)
+	if err != nil {
+		log.Errorf("Unable to render template: %s", err)
+		return
+	}
+
+	channel := viper.GetString("http.listeners.prometheus")
+	for _, msg := range msgs {
+		hl.irc.Privmsg(channel, msg)
+	}
+}

httplistener/templates.go

 	"github.issue":        "[{{b .Repository.Name}}] {{g .Sender.Login}} {{.Action}} issue #{{.Issue.Number}}: {{.Issue.Title}} {{.Issue.HTMLURL}}",
 	"github.issuecomment": "[{{b .Repository.Name}}] {{g .Comment.User.Login}} commented on issue #{{.Issue.Number}}: {{trunc .Comment.Body 150}} {{.Comment.HTMLURL}}",
 	"github.pullrequest":  "[{{b .Repository.Name}}] {{g .Sender.Login}} {{if .PullRequest.Merged}}merged{{else}}{{.Action}}{{end}} pull request #{{.PullRequest.Number}} (\x0303{{.PullRequest.Base.Ref}}…{{.PullRequest.Head.Ref}}\x0f): {{.PullRequest.Title}} {{.PullRequest.HTMLURL}}",
+	"prometheus.alert": `{{range .Alerts}}[{{b "Prometheus"}}] {{if (eq .Status "firing")}}{{b "alerting"}}{{else}}{{h "resolved"}}{{end}}: {{.Annotations.summary}}
+{{end}}`,
 }
 
 func refName(ref string) string {

webhook_test_data/prometheus/alert.json

+{
+  "version": "4",
+  "groupKey": "group",
+  "status": "firing",
+  "receiver": "irccat",
+  "groupLabels": {},
+  "commonLabels": {},
+  "commonAnnotations": {},
+  "externalURL": "http://alertmanager:9093",
+  "alerts": [
+    {
+      "status": "firing",
+      "labels": {
+	"alertname": "Test Alert",
+	"instance": "test.example.com",
+	"job": "jobname"
+      },
+      "annotations": {
+	"summary": "Alert summary"
+      },
+      "startsAt": "2019-11-10T23:20:50.52Z",
+      "endsAt": "2019-11-10T23:20:50.52Z",
+      "generatorURL": "http://prometheus:9090/graph?"
+    }
+  ]
+}

webhook_test_data/prometheus/resolved.json

+{
+  "version": "4",
+  "groupKey": "group",
+  "status": "firing",
+  "receiver": "irccat",
+  "groupLabels": {},
+  "commonLabels": {},
+  "commonAnnotations": {},
+  "externalURL": "http://alertmanager:9093",
+  "alerts": [
+    {
+      "status": "firing",
+      "labels": {
+	"alertname": "Test Alert",
+	"instance": "test.example.com",
+	"job": "jobname"
+      },
+      "annotations": {
+	"summary": "Alert summary"
+      },
+      "startsAt": "2019-11-10T23:20:50.52Z",
+      "endsAt": "2019-11-10T23:20:50.52Z",
+      "generatorURL": "http://prometheus:9090/graph?"
+    }
+  ]
+}