Merge pull request benjojo#3 from funkypenguin/master

Fix error checking, add Dockerfile

Author: benjojo

Dockerfile

@@ -0,0 +1,28 @@
+# Built following https://medium.com/@chemidy/create-the-smallest-and-secured-golang-docker-image-based-on-scratch-4752223b7324
+
+# STEP 1 build executable binary
+FROM golang:alpine as builder
+# Install SSL ca certificates
+RUN apk update && apk add git && apk add ca-certificates
+# Create appuser
+RUN adduser -D -g '' appuser
+COPY . $GOPATH/src/mypackage/myapp/
+WORKDIR $GOPATH/src/mypackage/myapp/
+#get dependancies
+RUN go get -d -v
+#build the binary
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -installsuffix cgo -ldflags="-w -s" -o /go/bin/alertmanager-discord
+
+
+# STEP 2 build a small image
+# start from scratch
+FROM scratch
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /etc/passwd /etc/passwd
+# Copy our static executable
+COPY --from=builder /go/bin/alertmanager-discord /go/bin/alertmanager-discord
+
+EXPOSE 9094
+USER appuser
+ENTRYPOINT ["/go/bin/alertmanager-discord"]
+

README.md

@@ -1,7 +1,7 @@
 alertmanager-discord
 ===
 
-Give this a webhook and point it as a webhook on alertmanager, and it will post your alerts into a discord channel for you as they trigger:
+Give this a webhook (with the DISCORD_WEBHOOK environment variable) and point it as a webhook on alertmanager, and it will post your alerts into a discord channel for you as they trigger:
 
 ![](/.github/demo.png)
 
@@ -31,4 +31,4 @@ receivers:
 - name: 'discord_webhook'
   webhook_configs:
   - url: 'http://localhost:9094'
-```
+```

main.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
+        "os"
 	"io/ioutil"
 	"net/http"
 	"strings"
@@ -44,9 +45,14 @@ type discordOut struct {
 }
 
 func main() {
-	webhookUrl := os.Getenv("webhook")
+	webhookUrl := os.Getenv("DISCORD_WEBHOOK")
+	if webhookUrl == "" {
+		fmt.Fprintf(os.Stderr, "error: environment variable DISCORD_WEBHOOK not found\n")
+        	os.Exit(1)
+	}
 	whURL := flag.String("webhook.url", webhookUrl, "")
 	flag.Parse()
+	fmt.Fprintf(os.Stdout, "info: Listening on 0.0.0.0:9094\n")
 	http.ListenAndServe(":9094", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		b, err := ioutil.ReadAll(r.Body)
 		if err != nil {
@@ -73,7 +79,7 @@ func main() {
 			if strings.Contains(realname, "localhost") && alert.Labels["exported_instance"] != "" {
 				realname = alert.Labels["exported_instance"]
 			}
-			Content += fmt.Sprintf("[%s]: %s on %s\n%s\n", strings.ToUpper(amo.Status), alert.Labels["alertname"], realname, alert.Annotations.Description)
+			Content += fmt.Sprintf("[%s]: %s on %s\n%s\n\n", strings.ToUpper(amo.Status), alert.Labels["alertname"], realname, alert.Annotations.Description)
 		}
 
 		DO.Content = Content + "```"