(tested) add hooks check when ping http route called

dist/example_config.yaml

@@ -66,6 +66,8 @@ mochi:
         # An array of routes to listen ping requests.
         # Used just to ensure if server is operational. Returns nothing,
         # just HTTP 200 without body. Listens both GET and HEAD HTTP methods.
+        # HEAD method just checks http server, GET checks all hooks,
+        # which support ping
         ping_routes:
             - "/ping"
 

frontend/frontend.go

@@ -30,4 +30,7 @@ type TrackerLogic interface {
 
 	// AfterScrape does something with the results of a Scrape after it has been completed.
 	AfterScrape(context.Context, *bittorrent.ScrapeRequest, *bittorrent.ScrapeResponse)
+
+	// Ping executes checks if all hooks are operational
+	Ping(context.Context) error
 }

frontend/http/frontend.go

@@ -308,6 +308,15 @@ func (f *Frontend) scrapeRoute(w http.ResponseWriter, r *http.Request, ps httpro
 	go f.logic.AfterScrape(ctx, req, resp)
 }
 
-func (f Frontend) ping(w http.ResponseWriter, _ *http.Request, _ httprouter.Params) {
-	w.WriteHeader(http.StatusOK)
+func (f Frontend) ping(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	var err error
+	if r.Method == http.MethodGet {
+		err = f.logic.Ping(context.Background())
+	}
+	if err == nil {
+		w.WriteHeader(http.StatusOK)
+	} else {
+		logger.Error().Err(err).Msg("ping completed with error")
+		w.WriteHeader(http.StatusServiceUnavailable)
+	}
 }

middleware/hooks.go

@@ -18,6 +18,16 @@ type Hook interface {
 	HandleScrape(context.Context, *bittorrent.ScrapeRequest, *bittorrent.ScrapeResponse) (context.Context, error)
 }
 
+// Pinger is an optional interface that may be implemented by a pre Hook
+// to check if it is operational. Used in frontend.TrackerLogic.
+//
+// It may be useful in cases when Hook performs foreign requests to
+// some external resources (i.e. storage) and `ping` request should
+// also check resource availability.
+type Pinger interface {
+	Ping(ctx context.Context) error
+}
+
 type skipSwarmInteraction struct{}
 
 // SkipSwarmInteractionKey is a key for the context of an Announce to control
@@ -205,3 +215,7 @@ func (h *responseHook) HandleScrape(ctx context.Context, req *bittorrent.ScrapeR
 
 	return ctx, nil
 }
+
+func (h *responseHook) Ping(_ context.Context) error {
+	return h.store.Ping()
+}

middleware/logic.go

@@ -19,12 +19,19 @@ var (
 // NewLogic creates a new instance of a TrackerLogic that executes the provided
 // middleware hooks.
 func NewLogic(annInterval, minAnnInterval time.Duration, peerStore storage.PeerStorage, preHooks, postHooks []Hook) *Logic {
-	return &Logic{
+	l := &Logic{
 		announceInterval:    annInterval,
 		minAnnounceInterval: minAnnInterval,
 		preHooks:            append(preHooks, &responseHook{store: peerStore}),
 		postHooks:           append(postHooks, &swarmInteractionHook{store: peerStore}),
+		pingers:             make([]Pinger, 0, 1),
 	}
+	for _, h := range l.preHooks {
+		if ph, isOk := h.(Pinger); isOk {
+			l.pingers = append(l.pingers, ph)
+		}
+	}
+	return l
 }
 
 // Logic is an implementation of the TrackerLogic that functions by
@@ -34,6 +41,7 @@ type Logic struct {
 	minAnnounceInterval time.Duration
 	preHooks            []Hook
 	postHooks           []Hook
+	pingers             []Pinger
 }
 
 // HandleAnnounce generates a response for an Announce.
@@ -101,6 +109,16 @@ func (l *Logic) AfterScrape(ctx context.Context, req *bittorrent.ScrapeRequest,
 	}
 }
 
+// Ping performs check if all Hook-s are operational
+func (l *Logic) Ping(ctx context.Context) (err error) {
+	for _, p := range l.pingers {
+		if err = p.Ping(ctx); err != nil {
+			break
+		}
+	}
+	return
+}
+
 // Stop stops the Logic.
 //
 // This stops any hooks that implement stop.Stopper.

storage/memory/storage.go

@@ -557,6 +557,10 @@ func (ps *peerStore) gc(cutoff time.Time) {
 	}
 }
 
+func (*peerStore) Ping() error {
+	return nil
+}
+
 func (ps *peerStore) Stop() stop.Result {
 	c := make(stop.Channel)
 	go func() {

storage/redis/storage.go

@@ -458,7 +458,7 @@ func (ps *store) GraduateLeecher(ih bittorrent.InfoHash, peer bittorrent.Peer) e
 	})
 }
 
-func (ps Connection) parsePeersList(peersResult *redis.StringSliceCmd) (peers []bittorrent.Peer, err error) {
+func (ps *Connection) parsePeersList(peersResult *redis.StringSliceCmd) (peers []bittorrent.Peer, err error) {
 	var peerIds []string
 	peerIds, err = peersResult.Result()
 	if err = AsNil(err); err == nil {
@@ -479,7 +479,7 @@ type getPeersFn func(context.Context, string, int) *redis.StringSliceCmd
 // converts result to bittorrent.Peer array.
 // If forSeeder set to true - returns only leechers, if false -
 // seeders and if maxCount not reached - leechers.
-func (ps Connection) GetPeers(ih bittorrent.InfoHash, forSeeder bool, maxCount int, isV6 bool, membersFn getPeersFn) (out []bittorrent.Peer, err error) {
+func (ps *Connection) GetPeers(ih bittorrent.InfoHash, forSeeder bool, maxCount int, isV6 bool, membersFn getPeersFn) (out []bittorrent.Peer, err error) {
 	infoHash := ih.RawString()
 
 	infoHashKeys := make([]string, 1, 2)
@@ -528,7 +528,7 @@ func (ps *store) AnnouncePeers(ih bittorrent.InfoHash, seeder bool, numWant int,
 
 type getPeerCountFn func(context.Context, string) *redis.IntCmd
 
-func (ps Connection) countPeers(infoHashKey string, countFn getPeerCountFn) uint32 {
+func (ps *Connection) countPeers(infoHashKey string, countFn getPeerCountFn) uint32 {
 	count, err := countFn(context.TODO(), infoHashKey).Result()
 	err = AsNil(err)
 	if err != nil {
@@ -538,7 +538,7 @@ func (ps Connection) countPeers(infoHashKey string, countFn getPeerCountFn) uint
 }
 
 // CountPeers calls provided countFn and returns seeders and leechers count for specified info hash
-func (ps Connection) CountPeers(ih bittorrent.InfoHash, countFn getPeerCountFn) (leechersCount, seedersCount uint32) {
+func (ps *Connection) CountPeers(ih bittorrent.InfoHash, countFn getPeerCountFn) (leechersCount, seedersCount uint32) {
 	infoHash := ih.RawString()
 
 	leechersCount = ps.countPeers(InfoHashKey(infoHash, false, false), countFn) +
@@ -562,7 +562,7 @@ func (ps *store) ScrapeSwarm(ih bittorrent.InfoHash) (leechers uint32, seeders u
 const argNumErrorMsg = "ERR wrong number of arguments"
 
 // Put - storage.DataStorage implementation
-func (ps Connection) Put(ctx string, values ...storage.Entry) (err error) {
+func (ps *Connection) Put(ctx string, values ...storage.Entry) (err error) {
 	if l := len(values); l > 0 {
 		if l == 1 {
 			err = ps.HSet(context.TODO(), PrefixKey+ctx, values[0].Key, values[0].Value).Err()
@@ -588,13 +588,13 @@ func (ps Connection) Put(ctx string, values ...storage.Entry) (err error) {
 }
 
 // Contains - storage.DataStorage implementation
-func (ps Connection) Contains(ctx string, key string) (bool, error) {
+func (ps *Connection) Contains(ctx string, key string) (bool, error) {
 	exist, err := ps.HExists(context.TODO(), PrefixKey+ctx, key).Result()
 	return exist, AsNil(err)
 }
 
 // Load - storage.DataStorage implementation
-func (ps Connection) Load(ctx string, key string) (v any, err error) {
+func (ps *Connection) Load(ctx string, key string) (v any, err error) {
 	v, err = ps.HGet(context.TODO(), PrefixKey+ctx, key).Result()
 	if err != nil && errors.Is(err, redis.Nil) {
 		v, err = nil, nil
@@ -603,7 +603,7 @@ func (ps Connection) Load(ctx string, key string) (v any, err error) {
 }
 
 // Delete - storage.DataStorage implementation
-func (ps Connection) Delete(ctx string, keys ...string) (err error) {
+func (ps *Connection) Delete(ctx string, keys ...string) (err error) {
 	if len(keys) > 0 {
 		err = AsNil(ps.HDel(context.TODO(), PrefixKey+ctx, keys...).Err())
 		if err != nil {
@@ -625,6 +625,11 @@ func (Connection) Preservable() bool {
 	return true
 }
 
+// Ping sends `PING` request to Redis server
+func (ps *Connection) Ping() error {
+	return ps.UniversalClient.Ping(context.TODO()).Err()
+}
+
 // GC deletes all Peers from the PeerStorage which are older than the
 // cutoff time.
 //

storage/storage.go

@@ -206,6 +206,10 @@ type PeerStorage interface {
 	// If the Swarm does not exist, an empty Scrape and no error is returned.
 	ScrapeSwarm(ih bittorrent.InfoHash) (leechers uint32, seeders uint32, snatched uint32)
 
+	// Ping used for checks if storage is alive
+	// (connection could be established, enough space etc.)
+	Ping() error
+
 	// Stopper is an interface that expects a Stop method to stop the PeerStorage.
 	// For more details see the documentation in the stop package.
 	stop.Stopper