feat: v0.4.0 simplify

watchdog.go

@@ -16,17 +16,16 @@ var (
 // Watchdog keeps checks to run either periodically
 // or on demand.
 type Watchdog struct {
-	checks []*wdCheck
+	checks map[string]*wdCheck
 	mu     sync.Mutex
 
-	monitoring bool // is monitoring currently in progress
-
 	events  chan CheckResult // output channel
 	limiter chan struct{}    // TODO: use proper limiter here
 
-	timeout time.Duration
+	timeout time.Duration // timeout for checks to complete
 
-	running int
+	monitoring bool // is monitoring currently in progress
+	running    int  // number of active checks monitored
 }
 
 type wdCheck struct {
@@ -37,29 +36,26 @@ type wdCheck struct {
 // New creates instance of Watchdog with
 // provided checks.
 func New(checks ...Check) *Watchdog {
-	ch := make([]*wdCheck, len(checks))
+	w := Watchdog{
+		checks: make(map[string]*wdCheck),
+	}
 
-	for i := range checks {
-		ch[i] = &wdCheck{
-			check: checks[i],
+	for _, c := range checks {
+		nc := &wdCheck{
+			check: c,
 		}
+
+		w.checks[c.Name] = nc
 	}
 
-	w := &Watchdog{
-		checks: ch,
-	}
-
-	return w
+	return &w
 }
 
 func (w *Watchdog) ListChecks() []Check {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	out := make([]Check, len(w.checks))
-	for i := range w.checks {
-		out[i] = w.checks[i].check
-	}
+	out := w.copyChecks()
 
 	return out
 }
@@ -81,20 +77,31 @@ func (w *Watchdog) SetTimeout(d time.Duration) {
 // AddChecks adds checks to the group.
 // If monitoring is in progress then monitoring it started for the newly added
 // check as well.
-// Check may have duplicate Name fields but note that RemoveChecks removes checks
-// by their Name fields.
+// Check may have not have duplicate Name fields. New check with the same
+// hame overwrites the previous one.
 func (w *Watchdog) AddChecks(checks ...Check) {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	for i := range checks {
+	if w.checks == nil {
+		w.checks = make(map[string]*wdCheck)
+	}
+
+	for _, c := range checks {
 		nc := &wdCheck{
-			check: checks[i],
+			check: c,
 		}
-		w.checks = append(w.checks, nc)
+
+		old, haveOld := w.checks[c.Name]
+
+		w.checks[c.Name] = nc
 
 		if w.monitoring {
 			w.startMonitoring(nc)
+
+			if haveOld {
+				w.stopMonitoring(old)
+			}
 		}
 	}
 }
@@ -104,19 +111,18 @@ func (w *Watchdog) RemoveChecks(names ...string) {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 
-	remaining := make([]*wdCheck, 0, len(w.checks)-len(names))
-	for _, c := range w.checks {
-		if slices.Contains(names, c.check.Name) {
-			if w.monitoring {
-				w.stopMonitoring(c)
-			}
+	for _, name := range names {
+		c, ok := w.checks[name]
+		if !ok {
 			continue
 		}
 
-		remaining = append(remaining, c)
-	}
+		if w.monitoring {
+			w.stopMonitoring(c)
+		}
 
-	w.checks = remaining
+		delete(w.checks, name)
+	}
 }
 
 // Start starts monitoring.
@@ -151,12 +157,10 @@ func (w *Watchdog) Start(concurrency int) (<-chan CheckResult, error) {
 	w.events = make(chan CheckResult, concurrency)
 	w.limiter = make(chan struct{}, concurrency)
 
-	for i := range w.checks {
-		w.startMonitoring(w.checks[i])
+	for _, c := range w.checks {
+		w.startMonitoring(c)
 	}
 
-	w.monitoring = true
-
 	return w.events, nil
 }
 
@@ -170,8 +174,8 @@ func (w *Watchdog) Stop() error {
 		return ErrNotRunning
 	}
 
-	for i := range w.checks {
-		w.stopMonitoring(w.checks[i])
+	for _, c := range w.checks {
+		w.stopMonitoring(c)
 	}
 
 	return nil
@@ -182,13 +186,14 @@ func (w *Watchdog) Stop() error {
 // Otherwise at most concurrency checks will be allowed to run simultaneously.
 func (w *Watchdog) RunImmediately(ctx context.Context, concurrency int) ([]CheckResult, error) {
 	w.mu.Lock()
+
 	if len(w.checks) == 0 {
 		w.mu.Unlock()
 		return nil, ErrNotConfigured
 	}
 
 	cp := w.copyChecks()
-	w.mu.Unlock() // release
+	w.mu.Unlock()
 
 	if concurrency == 0 {
 		concurrency = len(cp)
@@ -209,43 +214,26 @@ func (w *Watchdog) RunImmediately(ctx context.Context, concurrency int) ([]Check
 }
 
 func (w *Watchdog) copyChecks() []Check {
-	cp := make([]Check, len(w.checks))
-	for i := range w.checks {
-		cp[i] = w.checks[i].check
+	cp := make([]Check, 0, len(w.checks))
+	for _, v := range w.checks {
+		cp = append(cp, v.check)
 	}
 
 	return cp
 }
 
 func (w *Watchdog) startMonitoring(wdc *wdCheck) {
-
 	wdc.stop = make(chan struct{})
 	c := wdc.check
 
-	// this method is called only with
-	// w.mu locked
+	if !w.monitoring {
+		w.monitoring = true
+	}
+
 	w.running++
 
 	go func() {
-		defer func() {
-			w.mu.Lock()
-			defer w.mu.Unlock()
-
-			w.running--
-			if w.running == 0 {
-				// last goroutine to exit will also
-				// close the output chan
-				close(w.events)
-				w.monitoring = false
-			}
-		}()
-
-		state := CheckResult{
-			// if first run return anything
-			// other that OK, we'll report it
-			// if first run is OK, then we do not need to report
-			Status: StatusOK,
-		}
+		var curr error = nil
 
 		ticker := time.Tick(wdc.check.Interval)
 
@@ -255,21 +243,22 @@ func (w *Watchdog) startMonitoring(wdc *wdCheck) {
 			ctx, cancel := context.WithTimeout(context.Background(), w.timeout)
 			defer cancel()
 
-			status, err := c.Check(ctx)
+			err := c.Check(ctx)
 
 			<-w.limiter
 
-			s := CheckResult{
-				Name:   c.Name,
-				Status: status,
-				Error:  err,
+			r := CheckResult{
+				Name:  c.Name,
+				Error: err,
 			}
 
-			if s.Status != state.Status || s.Error != nil {
-				w.events <- s
+			if (err != nil && curr == nil) ||
+				(curr != nil && err == nil) {
+				// status changed, let's report
+				w.events <- r
 			}
 
-			state = s
+			curr = err
 
 			select {
 			case <-ticker:
@@ -284,50 +273,52 @@ func (w *Watchdog) startMonitoring(wdc *wdCheck) {
 
 func (w *Watchdog) stopMonitoring(wdc *wdCheck) {
 	close(wdc.stop)
+	w.running--
+
+	if w.running == 0 {
+		w.monitoring = false
+		close(w.events)
+	}
 }
 
 func runChecksConcurrently(ctx context.Context, ch []Check, concurrency int) []CheckResult {
-	statuses := make([]CheckResult, 0, len(ch))
-	m := sync.Mutex{} // for append operations
-
 	sema := make(chan struct{}, concurrency) // semaphore to limit concurrency
-	done := make(chan struct{}, len(ch))
-
-	count := len(ch)
+	done := make(chan CheckResult, len(ch))
 
+	wg := new(sync.WaitGroup)
+	wg.Add(len(ch))
 	for _, e := range ch {
-		sema <- struct{}{} // acquire
-		go func() error {
+		go func() {
+			sema <- struct{}{} // acquire
 			defer func() {
-				<-sema
-				done <- struct{}{}
+				<-sema // release
+				wg.Done()
 			}()
 
 			// relying on assumption that CheckFunc obeys context
 			// cancellation
-			status, err := e.Check(ctx)
+			err := e.Check(ctx)
 
 			r := CheckResult{
-				Name:   e.Name,
-				Status: status,
-				Error:  err,
+				Name:  e.Name,
+				Error: err,
 			}
 
-			m.Lock()
-			defer m.Unlock()
-			statuses = append(statuses, r)
-
-			return nil
+			done <- r
 		}()
 	}
 
-	// wait for all to finish
-	for range done {
-		count--
-		if count == 0 {
-			close(done)
-		}
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+
+	results := make([]CheckResult, 0, len(ch))
+
+	// collect results
+	for r := range done {
+		results = append(results, r)
 	}
 
-	return statuses
+	return results
 }