alertmanager-irc-relay/http.go

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// Copyright 2018 Google LLC
//
// 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
//
// https://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 main
import (
"bytes"
"encoding/json"
"io"
"io/ioutil"
"log"
"net/http"
"strconv"
"strings"
"text/template"
"github.com/gorilla/mux"
promtmpl "github.com/prometheus/alertmanager/template"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
var (
handledAlertGroups = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "webhook_handled_alert_groups",
Help: "Number of alert groups received"},
[]string{"ircchannel"},
)
handledAlerts = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "webhook_handled_alerts",
Help: "Number of single alert messages relayed"},
[]string{"ircchannel"},
)
alertHandlingErrors = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "webhook_alert_handling_errors",
Help: "Errors while processing webhook requests"},
[]string{"ircchannel", "error"},
)
)
type HTTPListener func(string, http.Handler) error
type HTTPServer struct {
StoppedRunning chan bool
Addr string
Port int
MsgTemplate *template.Template
MsgOnce bool
AlertMsgs chan AlertMsg
httpListener HTTPListener
}
func NewHTTPServer(config *Config, alertMsgs chan AlertMsg) (
*HTTPServer, error) {
return NewHTTPServerForTesting(config, alertMsgs, http.ListenAndServe)
}
func NewHTTPServerForTesting(config *Config, alertMsgs chan AlertMsg,
httpListener HTTPListener) (*HTTPServer, error) {
tmpl, err := template.New("msg").Parse(config.MsgTemplate)
if err != nil {
return nil, err
}
server := &HTTPServer{
StoppedRunning: make(chan bool),
Addr: config.HTTPHost,
Port: config.HTTPPort,
MsgTemplate: tmpl,
MsgOnce: config.MsgOnce,
AlertMsgs: alertMsgs,
httpListener: httpListener,
}
return server, nil
}
func (server *HTTPServer) FormatMsg(ircChannel string, data interface{}) string {
output := bytes.Buffer{}
var msg string
if err := server.MsgTemplate.Execute(&output, data); err != nil {
msg_bytes, _ := json.Marshal(data)
msg = string(msg_bytes)
log.Printf("Could not apply msg template on alert (%s): %s",
err, msg)
log.Printf("Sending raw alert")
alertHandlingErrors.WithLabelValues(ircChannel, "format_msg").Inc()
} else {
msg = output.String()
}
return msg
}
func (server *HTTPServer) GetMsgsFromAlertMessage(ircChannel string,
data *promtmpl.Data) []AlertMsg {
msgs := []AlertMsg{}
if server.MsgOnce {
msg := server.FormatMsg(ircChannel, data)
msgs = append(msgs,
AlertMsg{Channel: ircChannel, Alert: msg})
} else {
for _, alert := range data.Alerts {
msg := server.FormatMsg(ircChannel, alert)
msgs = append(msgs,
AlertMsg{Channel: ircChannel, Alert: msg})
}
}
return msgs
}
func (server *HTTPServer) RelayAlert(w http.ResponseWriter, r *http.Request) {
vars := mux.Vars(r)
ircChannel := "#" + vars["IRCChannel"]
body, err := ioutil.ReadAll(io.LimitReader(r.Body, 1024*1024*1024))
if err != nil {
log.Printf("Could not get body: %s", err)
alertHandlingErrors.WithLabelValues(ircChannel, "read_body").Inc()
return
}
var alertMessage = promtmpl.Data{}
if err := json.Unmarshal(body, &alertMessage); err != nil {
log.Printf("Could not decode request body (%s): %s", err, body)
alertHandlingErrors.WithLabelValues(ircChannel, "decode_body").Inc()
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
w.WriteHeader(422) // Unprocessable entity
if err := json.NewEncoder(w).Encode(err); err != nil {
log.Printf("Could not write decoding error: %s", err)
return
}
return
}
handledAlertGroups.WithLabelValues(ircChannel).Inc()
for _, alertMsg := range server.GetMsgsFromAlertMessage(
ircChannel, &alertMessage) {
select {
case server.AlertMsgs <- alertMsg:
handledAlerts.WithLabelValues(ircChannel).Inc()
default:
log.Printf("Could not send this alert to the IRC routine: %s",
alertMsg)
alertHandlingErrors.WithLabelValues(ircChannel, "internal_comm_channel_full").Inc()
}
}
}
func (server *HTTPServer) Run() {
router := mux.NewRouter().StrictSlash(true)
router.Path("/metrics").Handler(promhttp.Handler())
handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
server.RelayAlert(w, r)
})
router.Path("/{IRCChannel}").Handler(handler).Methods("POST")
listenAddr := strings.Join(
[]string{server.Addr, strconv.Itoa(server.Port)}, ":")
log.Printf("Starting HTTP server")
if err := server.httpListener(listenAddr, router); err != nil {
log.Printf("Could not start http server: %s", err)
}
server.StoppedRunning <- true
}