Override the timezone of incoming alerts

README.md

@@ -4,7 +4,7 @@ Basic XMPP Alertmanager Webhook Receiver for Prometheus
 
 ## Purpose
 
-This repository has been made to receive Prometheus alerts on my Phone without relying on a third party provider.  
+This repository has been made to receive Prometheus alerts on my Phone without relying on a third party provider.\
 To do so I have installed on my Raspberry PI:
 
  - [Prometheus](https://prometheus.io/)
@@ -31,6 +31,7 @@ This example of configuration file shows:
  - when the instance is starting, it sends to everyone `Prometheus Monitoring Started`
  - it sends a different message depending on a `severity` label
  - it sends a message when an alert is resolved
+ - it overrides the timezone to `Europe/Paris` (optional, can either `UTC`, `Local` or from the [list of timezones](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones)). By default it keeps the timezone from the message sent by Alertmanager
  - the templates are in plain text. The possible values are `text` or `html` using [XEP-0071](https://xmpp.org/extensions/xep-0071.html) which is deprecated. If omitted, it defaults to `text`
  - the program uses the XMPP user `monitoring@example.com` with a password
  - when it is working, it has the status `Monitoring Prometheus...`
@@ -44,8 +45,9 @@ This example of configuration file shows:
 {
     "listen": "127.0.0.1:9091",
     "startup_message": "Prometheus Monitoring Started",
-    "firing": "{{ if eq .Labels.severity \"error\" }}🔥{{ else if eq .Labels.severity \"warning\" }}💣{{ else }}💡{{ end }} Firing {{ .Labels.alertname }}\n{{ .Annotations.description }} since {{ .StartsAt }}\n{{ .GeneratorURL }}",
-    "resolved": "{{ .Labels.alertname }} resolved",
+    "firing": "{{ if eq .Labels.severity \"error\" }}🔥{{ else if eq .Labels.severity \"warning\" }}💣{{ else }}💡{{ end }} Firing {{ .Labels.alertname }}\n{{ .Annotations.description }} since {{ .StartsAt.Format \"2006-01-02 15:04:05\" }}\n{{ .GeneratorURL }}",
+    "resolved": "{{ .Labels.alertname }} resolved at {{ .EndsAt.Format \"2006-01-02 15:04:05\" }}",
+    "time_zone": "Europe/Paris",
     "format": "text",
     "xmpp": {
         "user": "monitoring@example.com",
@@ -69,7 +71,7 @@ This example of configuration file shows:
 
 ## Exotic DNS configuration
 
-Usually, the admin creates DNS records to resolve the XMPP server.  
+Usually, the admin creates DNS records to resolve the XMPP server.\
 In some circumstances such records are not created.
 
 The field `.xmpp.override_server` must be set to point to the right server:

alert_handler.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"net/http"
 	"text/template"
+	"time"
 
 	promTemplate "github.com/prometheus/alertmanager/template"
 )
@@ -14,6 +15,7 @@ type alertHandler struct {
 	sender           Sender
 	firingTemplate   *template.Template
 	resolvedTemplate *template.Template
+	timeLoc          *time.Location
 	format           Format
 }
 
@@ -23,6 +25,7 @@ func NewAlertHandler(config *Config, sender Sender) http.Handler {
 		sender:           sender,
 		firingTemplate:   config.Firing.ToTemplate(),
 		resolvedTemplate: config.Resolved.ToTemplate(),
+		timeLoc:          config.TimeZone.ToLocation(),
 		format:           config.Format,
 	}
 }
@@ -57,8 +60,12 @@ func (a *alertHandler) instantiateTemplate(tmpl *template.Template, alerts []pro
 		return
 	}
 
-	for alertIdx := range alerts {
-		if message := a.generateString(tmpl, &alerts[alertIdx]); message != "" {
+	for _, alert := range alerts {
+		if a.timeLoc != nil {
+			alert.StartsAt = alert.StartsAt.In(a.timeLoc)
+			alert.EndsAt = alert.EndsAt.In(a.timeLoc)
+		}
+		if message := a.generateString(tmpl, &alert); message != "" {
 			promAlertsProcessedMetric.Inc()
 			a.sender.Send(message, a.format)
 		}

config.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"strings"
 	"text/template"
+	"time"
 )
 
 // Config is the internal configuration type
@@ -17,6 +18,7 @@ type Config struct {
 	Resolved       *ConfigTemplate `json:"resolved"`
 	Format         Format          `json:"format"`
 	XMPP           ConfigXMPP      `json:"xmpp"`
+	TimeZone       *ConfigTimeZone `json:"time_zone"`
 }
 
 // ConfigXMPP is the configuration for XMPP connection
@@ -86,3 +88,24 @@ func (c *ConfigTemplate) UnmarshalJSON(b []byte) error {
 func (c *ConfigTemplate) ToTemplate() *template.Template {
 	return (*template.Template)(c)
 }
+
+// ConfigTimeZone
+
+type ConfigTimeZone time.Location
+
+func (c *ConfigTimeZone) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+
+	loc, err := time.LoadLocation(s)
+	if err == nil {
+		*c = ConfigTimeZone(*loc)
+	}
+	return err
+}
+
+func (c *ConfigTimeZone) ToLocation() *time.Location {
+	return (*time.Location)(c)
+}