feat: log version on startup

.github/workflows/publish-image.yml

@@ -71,6 +71,8 @@ jobs:
             ./docker-bake.hcl
             cwd://${{ steps.meta.outputs.bake-file }}
           targets: release
+          set: |
+            release.args.VERSION=${{ inputs.tag }}
           push: true
 
       # release-please creates the release as a draft so it only becomes visible

Dockerfile

@@ -7,7 +7,8 @@ RUN go mod download
 COPY *.go ./
 ARG TARGETOS=linux
 ARG TARGETARCH
-RUN CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -trimpath -ldflags="-s -w" -o /out/doormouse .
+ARG VERSION=dev
+RUN CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -trimpath -ldflags="-s -w -X main.version=$VERSION" -o /out/doormouse .
 
 FROM alpine:3.22
 

main.go

@@ -47,6 +47,10 @@ type Logger interface {
 
 const tcpScheme = "tcp://"
 
+// version is replaced by the release build. Keep a useful value for local
+// builds and tests that do not supply linker flags.
+var version = "dev"
+
 // shutdownGrace is how long in-flight requests get to finish on shutdown.
 const shutdownGrace = 15 * time.Second
 
@@ -1728,6 +1732,10 @@ func (l *StdLogger) Error(msg string, args ...interface{}) {
 	log.Printf("[ERROR] "+msg, args...)
 }
 
+func logStartup(logger Logger, version string) {
+	logger.Info("Starting doormouse version `%s`", version)
+}
+
 // warnUnreadableSSHKeys reports SSH keys the process cannot open. The key is
 // otherwise read only when a machine has gone idle, so a permissions mistake
 // stays invisible until the first shutdown silently fails, up to an
@@ -1760,6 +1768,9 @@ func warnUnreadableSSHKeys(config *ProxyConfig, logger Logger) {
 
 // Main function
 func main() {
+	logger := &StdLogger{}
+	logStartup(logger, version)
+
 	if len(os.Args) < 2 {
 		log.Fatal("Usage: doormouse <config.toml>")
 	}
@@ -1768,7 +1779,6 @@ func main() {
 
 	// Load configuration
 	clock := RealClock{}
-	logger := &StdLogger{}
 
 	MigrateConfigFile(configFile, logger)
 

main_test.go

@@ -324,6 +324,32 @@ type noopLogger struct{}
 func (noopLogger) Info(_ string, _ ...interface{})  {}
 func (noopLogger) Error(_ string, _ ...interface{}) {}
 
+type startupLogger struct {
+	info  []string
+	error []string
+}
+
+func (l *startupLogger) Info(msg string, args ...interface{}) {
+	l.info = append(l.info, fmt.Sprintf(msg, args...))
+}
+
+func (l *startupLogger) Error(msg string, args ...interface{}) {
+	l.error = append(l.error, fmt.Sprintf(msg, args...))
+}
+
+func TestLogStartup_LogsDoormouseVersionAtInfoLevel(t *testing.T) {
+	logger := &startupLogger{}
+
+	logStartup(logger, "2.1.0")
+
+	if len(logger.info) != 1 || logger.info[0] != "Starting doormouse version `2.1.0`" {
+		t.Fatalf("info logs = %q, want one startup version line", logger.info)
+	}
+	if len(logger.error) != 0 {
+		t.Fatalf("error logs = %q, want none", logger.error)
+	}
+}
+
 // ---------------------------------------------------------------------------
 // Test helpers
 // ---------------------------------------------------------------------------