Improve and fix module startup and shutdown procedures as well as error reporting

modules/error.go

@@ -2,11 +2,16 @@ package modules
 
 import (
 	"fmt"
+	"os"
 	"runtime/debug"
+	"sync"
+	"time"
 )
 
 var (
 	errorReportingChannel chan *ModuleError
+	reportToStdErr        bool
+	reportingLock         sync.RWMutex
 )
 
 // ModuleError wraps a panic, error or message into an error that can be reported.
@@ -64,12 +69,43 @@ func (me *ModuleError) Error() string {
 
 // Report reports the error through the configured reporting channel.
 func (me *ModuleError) Report() {
+	reportingLock.RLock()
+	defer reportingLock.RUnlock()
+
 	if errorReportingChannel != nil {
 		select {
 		case errorReportingChannel <- me:
 		default:
 		}
 	}
+
+	if reportToStdErr {
+		// default to writing to stderr
+		fmt.Fprintf(
+			os.Stderr,
+			`===== Error Report =====
+Message: %s
+Timestamp: %s
+ModuleName: %s
+TaskName: %s
+TaskType: %s
+Severity: %s
+PanicValue: %s
+StackTrace:
+
+%s
+===== End of Report =====
+`,
+			me.Message,
+			time.Now(),
+			me.ModuleName,
+			me.TaskName,
+			me.TaskType,
+			me.Severity,
+			me.PanicValue,
+			me.StackTrace,
+		)
+	}
 }
 
 // IsPanic returns whether the given error is a wrapped panic by the modules package and additionally returns it, if true.
@@ -84,7 +120,16 @@ func IsPanic(err error) (bool, *ModuleError) {
 
 // SetErrorReportingChannel sets the channel to report module errors through. By default only panics are reported, all other errors need to be manually wrapped into a *ModuleError and reported.
 func SetErrorReportingChannel(reportingChannel chan *ModuleError) {
-	if errorReportingChannel == nil {
+	reportingLock.Lock()
+	defer reportingLock.Unlock()
+
 	errorReportingChannel = reportingChannel
 }
+
+// SetStdErrReporting controls error reporting to stderr.
+func SetStdErrReporting(on bool) {
+	reportingLock.Lock()
+	defer reportingLock.Unlock()
+
+	reportToStdErr = on
 }

modules/modules.go

@@ -13,7 +13,7 @@ import (
 )
 
 var (
-	modulesLock sync.Mutex
+	modulesLock sync.RWMutex
 	modules     = make(map[string]*Module)
 
 	// ErrCleanExit is returned by Start() when the program is interrupted before starting. This can happen for example, when using the "--help" flag.
@@ -46,6 +46,10 @@ type Module struct {
 	microTaskCnt *int32
 	waitGroup    sync.WaitGroup
 
+	// events
+	eventHooks     map[string][]*eventHook
+	eventHooksLock sync.RWMutex
+
 	// dependency mgmt
 	depNames   []string
 	depModules []*Module
@@ -69,9 +73,9 @@ func (m *Module) shutdown() error {
 
 	// start shutdown function
 	m.waitGroup.Add(1)
-	stopFnError := make(chan error)
+	stopFnError := make(chan error, 1)
 	go func() {
-		stopFnError <- m.runModuleCtrlFn("stop module", m.stop)
+		stopFnError <- m.runCtrlFn("stop module", m.stop)
 		m.waitGroup.Done()
 	}()
 
@@ -84,16 +88,8 @@ func (m *Module) shutdown() error {
 
 	// wait for results
 	select {
-	case err := <-stopFnError:
-		return err
 	case <-done:
-		select {
+	case <-time.After(30 * time.Second):
-		case err := <-stopFnError:
-			return err
-		default:
-			return nil
-		}
-	case <-time.After(3 * time.Second):
 		log.Warningf(
 			"%s: timed out while waiting for workers/tasks to finish: workers=%d tasks=%d microtasks=%d, continuing shutdown...",
 			m.Name,
@@ -102,11 +98,18 @@ func (m *Module) shutdown() error {
 			atomic.LoadInt32(m.microTaskCnt),
 		)
 	}
+
+	// collect error
+	select {
+	case err := <-stopFnError:
+		return err
+	default:
+		log.Warningf(
+			"%s: timed out while waiting for stop function to finish, continuing shutdown...",
+			m.Name,
+		)
 		return nil
 	}
-
-func dummyAction() error {
-	return nil
 }
 
 // Register registers a new module. The control functions `prep`, `start` and `stop` are technically optional. `stop` is called _after_ all added module workers finished.
@@ -141,20 +144,10 @@ func initNewModule(name string, prep, start, stop func() error, dependencies ...
 		prep:         prep,
 		start:        start,
 		stop:         stop,
+		eventHooks:   make(map[string][]*eventHook),
 		depNames:     dependencies,
 	}
 
-	// replace nil arguments with dummy action
-	if newModule.prep == nil {
-		newModule.prep = dummyAction
-	}
-	if newModule.start == nil {
-		newModule.start = dummyAction
-	}
-	if newModule.stop == nil {
-		newModule.stop = dummyAction
-	}
-
 	return newModule
 }
 

modules/start.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"runtime"
+	"time"
 
 	"github.com/safing/portbase/log"
 	"github.com/tevino/abool"
@@ -26,8 +27,8 @@ func WaitForStartCompletion() <-chan struct{} {
 
 // Start starts all modules in the correct order. In case of an error, it will automatically shutdown again.
 func Start() error {
-	modulesLock.Lock()
+	modulesLock.RLock()
-	defer modulesLock.Unlock()
+	defer modulesLock.RUnlock()
 
 	// start microtask scheduler
 	go microTaskScheduler()
@@ -106,7 +107,11 @@ func prepareModules() error {
 				go func() {
 					reports <- &report{
 						module: execM,
-						err:    execM.runModuleCtrlFn("prep module", execM.prep),
+						err: execM.runCtrlFnWithTimeout(
+							"prep module",
+							10*time.Second,
+							execM.prep,
+						),
 					}
 				}()
 			}
@@ -154,7 +159,11 @@ func startModules() error {
 				go func() {
 					reports <- &report{
 						module: execM,
-						err:    execM.runModuleCtrlFn("start module", execM.start),
+						err: execM.runCtrlFnWithTimeout(
+							"start module",
+							60*time.Second,
+							execM.start,
+						),
 					}
 				}()
 			}

modules/stop.go

@@ -12,6 +12,8 @@ import (
 var (
 	shutdownSignal       = make(chan struct{})
 	shutdownSignalClosed = abool.NewBool(false)
+
+	shutdownCompleteSignal = make(chan struct{})
 )
 
 // ShuttingDown returns a channel read on the global shutdown signal.
@@ -45,6 +47,7 @@ func Shutdown() error {
 	}
 
 	log.Shutdown()
+	close(shutdownCompleteSignal)
 	return err
 }
 

modules/worker.go

@@ -3,6 +3,7 @@ package modules
 import (
 	"context"
 	"errors"
+	"fmt"
 	"sync/atomic"
 	"time"
 
@@ -101,7 +102,27 @@ func (m *Module) runWorker(name string, fn func(context.Context) error) (err err
 	return
 }
 
-func (m *Module) runModuleCtrlFn(name string, fn func() error) (err error) {
+func (m *Module) runCtrlFnWithTimeout(name string, timeout time.Duration, fn func() error) error {
+
+	stopFnError := make(chan error)
+	go func() {
+		stopFnError <- m.runCtrlFn(name, fn)
+	}()
+
+	// wait for results
+	select {
+	case err := <-stopFnError:
+		return err
+	case <-time.After(timeout):
+		return fmt.Errorf("timed out (%s)", timeout)
+	}
+}
+
+func (m *Module) runCtrlFn(name string, fn func() error) (err error) {
+	if fn == nil {
+		return
+	}
+
 	defer func() {
 		// recover from panic
 		panicVal := recover()