Initial commit

.github/workflows/docker-image.yaml

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+name: Build Docker Images
+
+on:
+  push:
+    tags:
+    - '**'
+    branches:
+    - 'main'
+  pull_request:
+    types:
+      - "opened"
+      - "reopened"
+      - "synchronize"
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push-image:
+    strategy:
+      matrix:
+        image: ["signal-http-bridge"]
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@v1
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}/${{ matrix.image }}
+          tags: |
+            type=semver,pattern={{version}}
+            type=edge
+            type=ref,event=pr
+
+      - name: Build and push Docker Images
+        uses: docker/build-push-action@v3
+        with:
+          context: .
+          file: Dockerfile
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          build-args: "TARGET=${{ matrix.image }}"

Dockerfile

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+# syntax=docker/dockerfile:1
+
+##
+## Build stage.
+##
+FROM golang:1.21.3-alpine AS build
+ENV GO111MODULE=on
+
+WORKDIR /app
+
+# Download dependencies
+COPY go.mod ./
+COPY go.sum ./
+RUN go mod download
+
+# Copy app
+COPY . .
+
+# build the actual binary
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o entry
+
+##
+## Deploy stage
+##
+FROM alpine:3.18
+
+# install common deps
+RUN apk add curl wget bash
+
+# copy the prebuilt file
+WORKDIR /
+COPY --from=build /app/entry /usr/bin/entry
+
+# set app as startup app
+ENTRYPOINT ["/usr/bin/entry"]

config.json

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+{
+  "signals": {
+    "USR1": "echo 'hallo'"
+  }
+}

go.mod

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+module github.com/deinstapel/signal-cmd-executor
+
+go 1.21.3
+
+require (
+	github.com/abiosoft/lineprefix v0.1.4 // indirect
+	github.com/fatih/color v1.12.0 // indirect
+	github.com/mattn/go-colorable v0.1.8 // indirect
+	github.com/mattn/go-isatty v0.0.12 // indirect
+	golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae // indirect
+)

go.sum

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+github.com/abiosoft/lineprefix v0.1.4 h1:fXu3jc+B2EaS98mTpEL5OH9EKv3scHRb7/gsvlqAD1A=
+github.com/abiosoft/lineprefix v0.1.4/go.mod h1:Myq9hfXs8e2OmHFvajp3pHxxThZL645XK+BrEQNvNSs=
+github.com/fatih/color v1.12.0 h1:mRhaKNwANqRgUBGKmnI5ZxEk7QXmjQeCcuYFMX2bfcc=
+github.com/fatih/color v1.12.0/go.mod h1:ELkj/draVOlAH/xkhN6mQ50Qd0MPOk5AAr3maGEBuJM=
+github.com/mattn/go-colorable v0.1.8 h1:c1ghPdyEDarC70ftn0y+A/Ee++9zz8ljHG1b13eJ0s8=
+github.com/mattn/go-colorable v0.1.8/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
+github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
+github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
+golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae h1:/WDfKMnPU+m5M4xB+6x4kaepxRw6jWvR5iDRdvjHgy8=
+golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

main.go

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+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"os/signal"
+	"syscall"
+
+	"github.com/abiosoft/lineprefix"
+)
+
+type Config struct {
+	Signals map[string]string `json:"signals"`
+}
+
+var signalMap = map[string]syscall.Signal{
+	"USR1": syscall.SIGUSR1,
+	"USR2": syscall.SIGUSR2,
+	"INT":  syscall.SIGINT,
+	"ABRT": syscall.SIGABRT,
+	"ALRM": syscall.SIGALRM,
+	"BUS":  syscall.SIGBUS,
+	"CHLD": syscall.SIGCHLD,
+	"CLD":  syscall.SIGCLD,
+	"CONT": syscall.SIGCONT,
+	"FPE":  syscall.SIGFPE,
+	"HUP":  syscall.SIGHUP,
+	"IO":   syscall.SIGIO,
+	"IOT":  syscall.SIGIOT,
+}
+
+// handles a single signal
+func handleSignal(ctx context.Context, signalName string, command string) {
+	c := make(chan os.Signal, 3)
+	signalNumber, ok := signalMap[signalName]
+	if !ok {
+		log.Fatalf("failed to find syscall for signal %v\n", signalName)
+	}
+
+	signal.Notify(c, signalNumber)
+
+	prefix := lineprefix.Prefix(fmt.Sprintf("[CMD SIG%v]", signalName))
+	stdoutWrapper := lineprefix.New(prefix, lineprefix.Writer(os.Stdout))
+	stderrWrapper := lineprefix.New(prefix, lineprefix.Writer(os.Stderr))
+
+outer:
+	for {
+		select {
+		case <-c:
+			cmd := exec.Command("/bin/bash", "-c", command)
+			cmd.Stderr = stderrWrapper
+			cmd.Stdout = stdoutWrapper
+			if err := cmd.Run(); err != nil {
+				log.Printf("WARNING: program terminated with error: %v\n", err)
+			}
+		case <-ctx.Done():
+			break outer
+		}
+	}
+
+	signal.Stop(c)
+	close(c)
+}
+
+// main entry point for the program, loads config file etc.
+func main() {
+	configFile, ok := os.LookupEnv("CONFIG_FILE")
+	if !ok {
+		configFile = "/etc/config.json"
+	}
+
+	configBytes, err := os.ReadFile(configFile)
+	if err != nil {
+		log.Fatalf("failed to read config file: %v\n", err)
+	}
+
+	config := Config{}
+	if err := json.Unmarshal(configBytes, &config); err != nil {
+		log.Fatalf("failed to deserialize config file: %v\n", err)
+	}
+
+	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGTERM)
+	defer cancel()
+
+	for signal, command := range config.Signals {
+		go handleSignal(ctx, signal, command)
+	}
+
+	<-ctx.Done()
+
+	log.Printf("exiting")
+}