Enable support for custom callbacks as part of maintenance (#2689)

* Enable support for custom callbacks as part of maintenance

This enables support for custom Maintenance callbacks as part of the periodic maintenance of silences and notification logs.
Effectively a no-op for the Alertmanager but allows downstream implementation to inject custom logic as part of it.

Signed-off-by: gotjosh <josue.abreu@gmail.com>

* Add tests

Signed-off-by: gotjosh <josue.abreu@gmail.com>

* Fix tests and remove whitespace

Signed-off-by: gotjosh <josue.abreu@gmail.com>

* Address review comments

Signed-off-by: gotjosh <josue.abreu@gmail.com>

* run go fmt

Signed-off-by: gotjosh <josue.abreu@gmail.com>

* Fix import ordering

Signed-off-by: gotjosh <josue.abreu@gmail.com>

cmd/alertmanager/main.go

@@ -267,7 +267,7 @@ func run() int {
 	notificationLogOpts := []nflog.Option{
 		nflog.WithRetention(*retention),
 		nflog.WithSnapshot(filepath.Join(*dataDir, "nflog")),
-		nflog.WithMaintenance(15*time.Minute, stopc, wg.Done),
+		nflog.WithMaintenance(15*time.Minute, stopc, wg.Done, nil),
 		nflog.WithMetrics(prometheus.DefaultRegisterer),
 		nflog.WithLogger(log.With(logger, "component", "nflog")),
 	}
@@ -304,7 +304,7 @@ func run() int {
 	// Start providers before router potentially sends updates.
 	wg.Add(1)
 	go func() {
-		silences.Maintenance(15*time.Minute, filepath.Join(*dataDir, "silences"), stopc)
+		silences.Maintenance(15*time.Minute, filepath.Join(*dataDir, "silences"), stopc, nil)
 		wg.Done()
 	}()
 

nflog/nflog.go

@@ -85,11 +85,16 @@ type Log struct {
 
 	// For now we only store the most recently added log entry.
 	// The key is a serialized concatenation of group key and receiver.
-	mtx       sync.RWMutex
-	st        state
-	broadcast func([]byte)
+	mtx                 sync.RWMutex
+	st                  state
+	broadcast           func([]byte)
+	maintenanceOverride MaintenanceFunc
 }
 
+// MaintenanceFunc represents the function to run as part of the periodic maintenance for the nflog.
+// It returns the size of the snapshot taken or an error if it failed.
+type MaintenanceFunc func() (int64, error)
+
 type metrics struct {
 	gcDuration              prometheus.Summary
 	snapshotDuration        prometheus.Summary
@@ -190,7 +195,8 @@ func WithMetrics(r prometheus.Registerer) Option {
 //
 // The maintenance terminates on receiving from the provided channel.
 // The done function is called after the final snapshot was completed.
-func WithMaintenance(d time.Duration, stopc chan struct{}, done func()) Option {
+// If not nil, the last argument is an override for what to do as part of the maintenance - for advanced usage.
+func WithMaintenance(d time.Duration, stopc chan struct{}, done func(), maintenanceOverride MaintenanceFunc) Option {
 	return func(l *Log) error {
 		if d == 0 {
 			return errors.New("maintenance interval must not be 0")
@@ -198,6 +204,7 @@ func WithMaintenance(d time.Duration, stopc chan struct{}, done func()) Option {
 		l.runInterval = d
 		l.stopc = stopc
 		l.done = done
+		l.maintenanceOverride = maintenanceOverride
 		return nil
 	}
 }
@@ -325,34 +332,40 @@ func (l *Log) run() {
 	t := time.NewTicker(l.runInterval)
 	defer t.Stop()
 
+	var doMaintenance MaintenanceFunc
+	doMaintenance = func() (int64, error) {
+		var size int64
+		if _, err := l.GC(); err != nil {
+			return size, err
+		}
+		if l.snapf == "" {
+			return size, nil
+		}
+		f, err := openReplace(l.snapf)
+		if err != nil {
+			return size, err
+		}
+		if size, err = l.Snapshot(f); err != nil {
+			return size, err
+		}
+		return size, f.Close()
+	}
+
+	if l.maintenanceOverride != nil {
+		doMaintenance = l.maintenanceOverride
+	}
+
 	if l.done != nil {
 		defer l.done()
 	}
 
-	f := func() error {
+	runMaintenance := func(do func() (int64, error)) error {
 		start := l.now()
-		var size int64
-
 		level.Debug(l.logger).Log("msg", "Running maintenance")
-		defer func() {
-			level.Debug(l.logger).Log("msg", "Maintenance done", "duration", l.now().Sub(start), "size", size)
-			l.metrics.snapshotSize.Set(float64(size))
-		}()
-
-		if _, err := l.GC(); err != nil {
-			return err
-		}
-		if l.snapf == "" {
-			return nil
-		}
-		f, err := openReplace(l.snapf)
-		if err != nil {
-			return err
-		}
-		if size, err = l.Snapshot(f); err != nil {
-			return err
-		}
-		return f.Close()
+		size, err := do()
+		level.Debug(l.logger).Log("msg", "Maintenance done", "duration", l.now().Sub(start), "size", size)
+		l.metrics.snapshotSize.Set(float64(size))
+		return err
 	}
 
 Loop:
@@ -361,7 +374,7 @@ Loop:
 		case <-l.stopc:
 			break Loop
 		case <-t.C:
-			if err := f(); err != nil {
+			if err := runMaintenance(doMaintenance); err != nil {
 				level.Error(l.logger).Log("msg", "Running maintenance failed", "err", err)
 			}
 		}
@@ -370,7 +383,7 @@ Loop:
 	if l.snapf == "" {
 		return
 	}
-	if err := f(); err != nil {
+	if err := runMaintenance(doMaintenance); err != nil {
 		level.Error(l.logger).Log("msg", "Creating shutdown snapshot failed", "err", err)
 	}
 }

nflog/nflog_test.go

@@ -18,10 +18,13 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"sync"
 	"testing"
 	"time"
 
 	pb "github.com/prometheus/alertmanager/nflog/nflogpb"
+
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/stretchr/testify/require"
 )
 
@@ -123,6 +126,33 @@ func TestLogSnapshot(t *testing.T) {
 	}
 }
 
+func TestWithMaintenance_SupportsCustomCallback(t *testing.T) {
+	f, err := ioutil.TempFile("", "snapshot")
+	require.NoError(t, err, "creating temp file failed")
+
+	stopc := make(chan struct{})
+	var mtx sync.Mutex
+	var mc int
+	l, err := New(WithMetrics(prometheus.NewPedanticRegistry()), WithSnapshot(f.Name()), WithMaintenance(100*time.Millisecond, stopc, nil, func() (int64, error) {
+		mtx.Lock()
+		mc++
+		mtx.Unlock()
+
+		return 0, nil
+	}))
+	require.NoError(t, err)
+
+	go l.run()
+	time.Sleep(200 * time.Millisecond)
+	close(stopc)
+
+	require.Eventually(t, func() bool {
+		mtx.Lock()
+		defer mtx.Unlock()
+		return mc >= 2
+	}, 500*time.Millisecond, 100*time.Millisecond)
+}
+
 func TestReplaceFile(t *testing.T) {
 	dir, err := ioutil.TempDir("", "replace_file")
 	require.NoError(t, err, "creating temp dir failed")

silence/silence.go

@@ -201,6 +201,10 @@ type Silences struct {
 	mc        matcherCache
 }
 
+// MaintenanceFunc represents the function to run as part of the periodic maintenance for silences.
+// It returns the size of the snapshot taken or an error if it failed.
+type MaintenanceFunc func() (int64, error)
+
 type metrics struct {
 	gcDuration              prometheus.Summary
 	snapshotDuration        prometheus.Summary
@@ -349,34 +353,42 @@ func New(o Options) (*Silences, error) {
 // Maintenance garbage collects the silence state at the given interval. If the snapshot
 // file is set, a snapshot is written to it afterwards.
 // Terminates on receiving from stopc.
-func (s *Silences) Maintenance(interval time.Duration, snapf string, stopc <-chan struct{}) {
+// If not nil, the last argument is an override for what to do as part of the maintenance - for advanced usage.
+func (s *Silences) Maintenance(interval time.Duration, snapf string, stopc <-chan struct{}, override MaintenanceFunc) {
 	t := time.NewTicker(interval)
 	defer t.Stop()
 
-	f := func() error {
-		start := s.now()
+	var doMaintenance MaintenanceFunc
+	doMaintenance = func() (int64, error) {
 		var size int64
 
-		level.Debug(s.logger).Log("msg", "Running maintenance")
-		defer func() {
-			level.Debug(s.logger).Log("msg", "Maintenance done", "duration", s.now().Sub(start), "size", size)
-			s.metrics.snapshotSize.Set(float64(size))
-		}()
-
 		if _, err := s.GC(); err != nil {
-			return err
+			return size, err
 		}
 		if snapf == "" {
-			return nil
+			return size, nil
 		}
 		f, err := openReplace(snapf)
 		if err != nil {
-			return err
+			return size, err
 		}
 		if size, err = s.Snapshot(f); err != nil {
-			return err
+			return size, err
 		}
-		return f.Close()
+		return size, f.Close()
+	}
+
+	if doMaintenance != nil {
+		doMaintenance = override
+	}
+
+	runMaintenance := func(do MaintenanceFunc) error {
+		start := s.now()
+		level.Debug(s.logger).Log("msg", "Running maintenance")
+		size, err := do()
+		level.Debug(s.logger).Log("msg", "Maintenance done", "duration", s.now().Sub(start), "size", size)
+		s.metrics.snapshotSize.Set(float64(size))
+		return err
 	}
 
 Loop:
@@ -385,7 +397,7 @@ Loop:
 		case <-stopc:
 			break Loop
 		case <-t.C:
-			if err := f(); err != nil {
+			if err := runMaintenance(doMaintenance); err != nil {
 				level.Info(s.logger).Log("msg", "Running maintenance failed", "err", err)
 			}
 		}
@@ -394,7 +406,7 @@ Loop:
 	if snapf == "" {
 		return
 	}
-	if err := f(); err != nil {
+	if err := runMaintenance(doMaintenance); err != nil {
 		level.Info(s.logger).Log("msg", "Creating shutdown snapshot failed", "err", err)
 	}
 }

silence/silence_test.go

@@ -19,6 +19,7 @@ import (
 	"io/ioutil"
 	"os"
 	"sort"
+	"sync"
 	"testing"
 	"time"
 
@@ -179,6 +180,32 @@ func TestSilencesSnapshot(t *testing.T) {
 	}
 }
 
+func TestSilences_Maintenance_SupportsCustomCallback(t *testing.T) {
+	f, err := ioutil.TempFile("", "snapshot")
+	require.NoError(t, err, "creating temp file failed")
+	s := &Silences{st: state{}, logger: log.NewNopLogger(), now: utcNow, metrics: newMetrics(nil, nil)}
+	stopc := make(chan struct{})
+	var mtx sync.Mutex
+	var mc int
+
+	go s.Maintenance(100*time.Millisecond, f.Name(), stopc, func() (int64, error) {
+		mtx.Lock()
+		mc++
+		mtx.Unlock()
+
+		return 0, nil
+	})
+
+	time.Sleep(200 * time.Millisecond)
+	close(stopc)
+
+	require.Eventually(t, func() bool {
+		mtx.Lock()
+		defer mtx.Unlock()
+		return mc >= 2 // At least, one for the regular schedule and one at shutdown.
+	}, 500*time.Millisecond, 100*time.Millisecond)
+}
+
 func TestSilencesSetSilence(t *testing.T) {
 	s, err := New(Options{
 		Retention: time.Minute,