providers: optimize GC

1. Don't be n^2.
2. Don't bother walking the cache, just drop it.

providers/providers.go

@@ -68,7 +68,7 @@ func NewProviderManager(ctx context.Context, local peer.ID, dstore ds.Batching)
 
 	pm.proc = goprocessctx.WithContext(ctx)
 	pm.cleanupInterval = defaultCleanupInterval
-	pm.proc.Go(func(p goprocess.Process) { pm.run() })
+	pm.proc.Go(pm.run)
 
 	return pm
 }
@@ -191,69 +191,49 @@ func writeProviderEntry(dstore ds.Datastore, k cid.Cid, p peer.ID, t time.Time)
 	return dstore.Put(ds.NewKey(dsk), buf[:n])
 }
 
-func (pm *ProviderManager) deleteProvSet(k cid.Cid) error {
-	pm.providers.Remove(k)
-
+func (pm *ProviderManager) gc() {
 	res, err := pm.dstore.Query(dsq.Query{
 		KeysOnly: true,
-		Prefix:   mkProvKey(k),
+		Prefix:   providersKeyPrefix,
 	})
 	if err != nil {
-		return err
-	}
-
-	entries, err := res.Rest()
-	if err != nil {
-		return err
+		log.Error("error garbage collecting provider records: ", err)
+		return
 	}
+	defer res.Close()
 
-	for _, e := range entries {
-		err := pm.dstore.Delete(ds.NewKey(e.Key))
-		if err != nil {
-			log.Error("deleting provider set: ", err)
+	now := time.Now()
+	for {
+		e, ok := res.NextSync()
+		if !ok {
+			return
 		}
-	}
-	return nil
-}
-
-func (pm *ProviderManager) getProvKeys() (func() (cid.Cid, bool), error) {
-	res, err := pm.dstore.Query(dsq.Query{
-		KeysOnly: true,
-		Prefix:   providersKeyPrefix,
-	})
-	if err != nil {
-		return nil, err
-	}
 
-	iter := func() (cid.Cid, bool) {
-		for e := range res.Next() {
-			parts := strings.Split(e.Key, "/")
-			if len(parts) != 4 {
-				log.Warningf("incorrectly formatted provider entry in datastore: %s", e.Key)
-				continue
-			}
-			decoded, err := base32.RawStdEncoding.DecodeString(parts[2])
-			if err != nil {
-				log.Warning("error decoding base32 provider key: %s: %s", parts[2], err)
-				continue
-			}
+		if e.Error != nil {
+			log.Error("got an error: ", e.Error)
+			continue
+		}
 
-			c, err := cid.Cast(decoded)
+		// check expiration time
+		t, err := readTimeValue(e.Value)
+		switch {
+		case err != nil:
+			// couldn't parse the time
+			log.Warning("parsing providers record from disk: ", err)
+			fallthrough
+		case now.Sub(t) > ProvideValidity:
+			// or just expired
+			err = pm.dstore.Delete(ds.RawKey(e.Key))
 			if err != nil {
-				log.Warning("error casting key to cid from datastore key: %s", err)
-				continue
+				log.Warning("failed to remove provider record from disk: ", err)
 			}
-
-			return c, true
 		}
-		return cid.Cid{}, false
 	}
-
-	return iter, nil
 }
 
-func (pm *ProviderManager) run() {
+func (pm *ProviderManager) run(proc goprocess.Process) {
 	tick := time.NewTicker(pm.cleanupInterval)
+	defer tick.Stop()
 	for {
 		select {
 		case np := <-pm.newprovs:
@@ -267,47 +247,16 @@ func (pm *ProviderManager) run() {
 				log.Error("error reading providers: ", err)
 			}
 
-			gp.resp <- provs
+			// set the cap so the user can't append to this.
+			gp.resp <- provs[0:len(provs):len(provs)]
 		case <-tick.C:
-			keys, err := pm.getProvKeys()
-			if err != nil {
-				log.Error("Error loading provider keys: ", err)
-				continue
-			}
-			now := time.Now()
-			for {
-				k, ok := keys()
-				if !ok {
-					break
-				}
-
-				provs, err := pm.getProvSet(k)
-				if err != nil {
-					log.Error("error loading known provset: ", err)
-					continue
-				}
-				for p, t := range provs.set {
-					if now.Sub(t) > ProvideValidity {
-						delete(provs.set, p)
-					}
-				}
-				// have we run out of providers?
-				if len(provs.set) == 0 {
-					provs.providers = nil
-					err := pm.deleteProvSet(k)
-					if err != nil {
-						log.Error("error deleting provider set: ", err)
-					}
-				} else if len(provs.set) < len(provs.providers) {
-					// We must have modified the providers set, recompute.
-					provs.providers = make([]peer.ID, 0, len(provs.set))
-					for p := range provs.set {
-						provs.providers = append(provs.providers, p)
-					}
-				}
-			}
-		case <-pm.proc.Closing():
-			tick.Stop()
+			// You know the wonderful thing about caches? You can
+			// drop them.
+			//
+			// Much faster than GCing.
+			pm.providers.Purge()
+			pm.gc()
+		case <-proc.Closing():
 			return
 		}
 	}

providers/providers_test.go

@@ -10,6 +10,8 @@ import (
 
 	cid "github.com/ipfs/go-cid"
 	ds "github.com/ipfs/go-datastore"
+	dsq "github.com/ipfs/go-datastore/query"
+	dssync "github.com/ipfs/go-datastore/sync"
 	u "github.com/ipfs/go-ipfs-util"
 	peer "github.com/libp2p/go-libp2p-peer"
 	//
@@ -22,7 +24,7 @@ func TestProviderManager(t *testing.T) {
 	defer cancel()
 
 	mid := peer.ID("testing")
-	p := NewProviderManager(ctx, mid, ds.NewMapDatastore())
+	p := NewProviderManager(ctx, mid, dssync.MutexWrap(ds.NewMapDatastore()))
 	a := cid.NewCidV0(u.Hash([]byte("test")))
 	p.AddProvider(ctx, a, peer.ID("testingprovider"))
 	resp := p.GetProviders(ctx, a)
@@ -41,7 +43,7 @@ func TestProvidersDatastore(t *testing.T) {
 	defer cancel()
 
 	mid := peer.ID("testing")
-	p := NewProviderManager(ctx, mid, ds.NewMapDatastore())
+	p := NewProviderManager(ctx, mid, dssync.MutexWrap(ds.NewMapDatastore()))
 	defer p.proc.Close()
 
 	friend := peer.ID("friend")
@@ -64,7 +66,7 @@ func TestProvidersDatastore(t *testing.T) {
 }
 
 func TestProvidersSerialization(t *testing.T) {
-	dstore := ds.NewMapDatastore()
+	dstore := dssync.MutexWrap(ds.NewMapDatastore())
 
 	k := cid.NewCidV0(u.Hash(([]byte("my key!"))))
 	p1 := peer.ID("peer one")
@@ -120,7 +122,7 @@ func TestProvidesExpire(t *testing.T) {
 	defer cancel()
 
 	mid := peer.ID("testing")
-	p := NewProviderManager(ctx, mid, ds.NewMapDatastore())
+	p := NewProviderManager(ctx, mid, dssync.MutexWrap(ds.NewMapDatastore()))
 
 	peers := []peer.ID{"a", "b"}
 	var cids []cid.Cid
@@ -150,13 +152,15 @@ func TestProvidesExpire(t *testing.T) {
 		t.Fatal("providers map not cleaned up")
 	}
 
-	proviter, err := p.getProvKeys()
+	res, err := p.dstore.Query(dsq.Query{Prefix: providersKeyPrefix})
 	if err != nil {
 		t.Fatal(err)
 	}
-
-	_, ok := proviter()
-	if ok {
+	rest, err := res.Rest()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(rest) > 0 {
 		t.Fatal("expected everything to be cleaned out of the datastore")
 	}
 }
@@ -229,7 +233,7 @@ func TestUponCacheMissProvidersAreReadFromDatastore(t *testing.T) {
 	p1, p2 := peer.ID("a"), peer.ID("b")
 	c1 := cid.NewCidV1(cid.DagCBOR, u.Hash([]byte("1")))
 	c2 := cid.NewCidV1(cid.DagCBOR, u.Hash([]byte("2")))
-	pm := NewProviderManager(ctx, p1, ds.NewMapDatastore())
+	pm := NewProviderManager(ctx, p1, dssync.MutexWrap(ds.NewMapDatastore()))
 
 	pm.AddProvider(ctx, c1, p1)
 	// make the cached provider for c1 go to datastore