Move common code to launcher.go

control/cmd/control/main.go

@@ -100,11 +100,13 @@ var globalCfg config.Config
 
 func main() {
 	application := launcher.Application{
-		TOMLConfig: &globalCfg,
-		ShortName:  "SCION Control Service",
-		// TODO(scrye): Deprecated additional sampler, remove once Anapaya/scion#5000 is in.
-		Samplers: []func(command.Pather) *cobra.Command{newSamplePolicy},
-		Main:     realMain,
+		ApplicationBase: launcher.ApplicationBase{
+			TOMLConfig: &globalCfg,
+			ShortName:  "SCION Control Service",
+			// TODO(scrye): Deprecated additional sampler, remove once Anapaya/scion#5000 is in.
+			Samplers: []func(command.Pather) *cobra.Command{newSamplePolicy},
+			Main:     realMain,
+		},
 	}
 	application.Run()
 }

daemon/cmd/daemon/main.go

@@ -75,9 +75,11 @@ var globalCfg config.Config
 
 func main() {
 	application := launcher.Application{
-		TOMLConfig: &globalCfg,
-		ShortName:  "SCION Daemon",
-		Main:       realMain,
+		ApplicationBase: launcher.ApplicationBase{
+			TOMLConfig: &globalCfg,
+			ShortName:  "SCION Daemon",
+			Main:       realMain,
+		},
 	}
 	application.Run()
 }

dispatcher/cmd/dispatcher/main.go

@@ -47,10 +47,12 @@ var globalCfg config.Config
 
 func main() {
 	application := launcher.Application{
-		TOMLConfig:  &globalCfg,
-		ShortName:   "SCION Dispatcher",
-		RequiredIPs: requiredIPs,
-		Main:        realMain,
+		ApplicationBase: launcher.ApplicationBase{
+			TOMLConfig:  &globalCfg,
+			ShortName:   "SCION Dispatcher",
+			RequiredIPs: requiredIPs,
+			Main:        realMain,
+		},
 	}
 	application.Run()
 }

gateway/cmd/gateway/main.go

@@ -43,9 +43,11 @@ var globalCfg config.Config
 
 func main() {
 	application := launcher.Application{
-		TOMLConfig: &globalCfg,
-		ShortName:  "SCION IP Gateway",
-		Main:       realMain,
+		ApplicationBase: launcher.ApplicationBase{
+			TOMLConfig: &globalCfg,
+			ShortName:  "SCION IP Gateway",
+			Main:       realMain,
+		},
 	}
 	application.Run()
 }

private/app/launcher/BUILD.bazel

@@ -14,15 +14,60 @@ go_library(
         "//pkg/log:go_default_library",
         "//pkg/private/prom:go_default_library",
         "//pkg/private/serrors:go_default_library",
-        "//private/app:go_default_library",
         "//private/app/command:go_default_library",
         "//private/config:go_default_library",
         "//private/env:go_default_library",
         "@com_github_prometheus_client_golang//prometheus:go_default_library",
         "@com_github_prometheus_client_golang//prometheus/promauto:go_default_library",
         "@com_github_spf13_cobra//:go_default_library",
         "@com_github_spf13_viper//:go_default_library",
-    ],
+    ] + select({
+        "@io_bazel_rules_go//go/platform:aix": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:android": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:darwin": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:dragonfly": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:freebsd": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:illumos": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:ios": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:js": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:linux": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:netbsd": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:openbsd": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:plan9": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:solaris": [
+            "//private/app:go_default_library",
+        ],
+        "@io_bazel_rules_go//go/platform:windows": [
+            "@org_golang_x_sys//windows/svc:go_default_library",
+            "@org_golang_x_sys//windows/svc/debug:go_default_library",
+            "@org_golang_x_sys//windows/svc/eventlog:go_default_library",
+        ],
+        "//conditions:default": [],
+    }),
 )
 
 go_test(

private/app/launcher/launcher.go

@@ -17,15 +17,23 @@
 package launcher
 
 import (
+	"context"
 	"fmt"
+	"io"
+	"net"
+	"os"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 
 	"github.com/scionproto/scion/pkg/log"
+	"github.com/scionproto/scion/pkg/private/prom"
+	"github.com/scionproto/scion/pkg/private/serrors"
 	"github.com/scionproto/scion/private/app/command"
 	"github.com/scionproto/scion/private/config"
+	libconfig "github.com/scionproto/scion/private/config"
 	"github.com/scionproto/scion/private/env"
 )
 
@@ -38,6 +46,138 @@ const (
 	cfgConfigFile                = "config"
 )
 
+// ApplicationBase provides common launcher functions for a SCION server application.
+type ApplicationBase struct {
+	// TOMLConfig holds the Go data structure for the application-specific
+	// TOML configuration. The Application launcher will check if the TOMLConfig
+	// supports additional methods (e.g., custom logging or instance ID) and
+	// extract them from the config if that is the case. See the XxxConfig interfaces
+	// in this package for more information.
+	TOMLConfig libconfig.Config
+
+	// Samplers contains additional configuration samplers to be included
+	// under the sample subcommand. If empty, no additional samplers are
+	// listed.
+	//
+	// DEPRECATED. This field will be removed once Anapaya/scion#5000 is implemented.
+	Samplers []func(command.Pather) *cobra.Command
+
+	// ShortName is the short name of the application. If empty, the executable name is used.
+	// The ShortName could be, for example, "SCION Daemon" for the SCION Daemon.
+	ShortName string
+
+	// RequiredIPs should return the IPs that this application wants to listen
+	// on. The launcher will wait until those IPs can be listened on. The
+	// function is called after the configuration has been  initialized. If this
+	// function is not set the launcher will immediately start the application
+	// without waiting for any IPs.
+	RequiredIPs func() ([]net.IP, error)
+
+	// Main is the custom logic of the application. If nil, no custom logic is executed
+	// (and only the setup/teardown harness runs). If Main returns an error, the
+	// Run method will return a non-zero exit code.
+	Main func(ctx context.Context) error
+
+	// ErrorWriter specifies where error output should be printed. If nil, os.Stderr is used.
+	ErrorWriter io.Writer
+
+	// config contains the Viper configuration KV store.
+	config *viper.Viper
+}
+
+func (a *ApplicationBase) getShortName(executable string) string {
+	if a.ShortName != "" {
+		return a.ShortName
+	}
+	return executable
+}
+
+func (a *ApplicationBase) loadConfig() error {
+	os.Setenv("TZ", "UTC")
+
+	// Load launcher configurations from the same config file as the custom
+	// application configuration.
+	a.config.SetConfigType("toml")
+	a.config.SetConfigFile(a.config.GetString(cfgConfigFile))
+	if err := a.config.ReadInConfig(); err != nil {
+		return serrors.Wrap("loading generic server config from file", err,
+			"file", a.config.GetString(cfgConfigFile))
+
+	}
+
+	if err := libconfig.LoadFile(a.config.GetString(cfgConfigFile), a.TOMLConfig); err != nil {
+		return serrors.Wrap("loading config from file", err,
+			"file", a.config.GetString(cfgConfigFile))
+
+	}
+	a.TOMLConfig.InitDefaults()
+	return nil
+}
+
+func (a *ApplicationBase) initLogging() error {
+	logEntriesTotal := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "lib_log_emitted_entries_total",
+			Help: "Total number of log entries emitted.",
+		},
+		[]string{"level"},
+	)
+	opt := log.WithEntriesCounter(log.EntriesCounter{
+		Debug: logEntriesTotal.With(prometheus.Labels{"level": "debug"}),
+		Info:  logEntriesTotal.With(prometheus.Labels{"level": "info"}),
+		Error: logEntriesTotal.With(prometheus.Labels{"level": "error"}),
+	})
+	if err := log.Setup(a.getLogging(), opt); err != nil {
+		return serrors.Wrap("initialize logging", err)
+	}
+	return nil
+}
+
+func (a *ApplicationBase) executeCommand(ctx context.Context, shortName string) error {
+
+	defer log.Flush()
+	if a.RequiredIPs != nil {
+		ips, err := a.RequiredIPs()
+		if err != nil {
+			return serrors.Wrap("loading required IPs", err)
+		}
+		WaitForNetworkReady(ctx, ips)
+	}
+	if err := env.LogAppStarted(shortName, a.config.GetString(cfgGeneralID)); err != nil {
+		return err
+	}
+	defer env.LogAppStopped(shortName, a.config.GetString(cfgGeneralID))
+	defer log.HandlePanic()
+
+	exportBuildInfo()
+	prom.ExportElementID(a.config.GetString(cfgGeneralID))
+	if err := a.TOMLConfig.Validate(); err != nil {
+		return serrors.Wrap("validate config", err)
+	}
+
+	if a.Main == nil {
+		return nil
+	}
+	return a.Main(ctx)
+}
+
+func (a *ApplicationBase) getLogging() log.Config {
+	return log.Config{
+		Console: log.ConsoleConfig{
+			Level:           a.config.GetString(cfgLogConsoleLevel),
+			Format:          a.config.GetString(cfgLogConsoleFormat),
+			StacktraceLevel: a.config.GetString(cfgLogConsoleStacktraceLevel),
+		},
+	}
+}
+
+func (a *ApplicationBase) getErrorWriter() io.Writer {
+	if a.ErrorWriter != nil {
+		return a.ErrorWriter
+	}
+	return os.Stderr
+}
+
 // LoggingConfig is implemented by configurations that define logging behavior.
 // If a application configuration does not implement this interface, then a
 // default logging configuration is used.