Recreate blob cache if missing (closes #104)

archiver.go

@@ -76,21 +76,16 @@ func (arch *Archiver) Preload() error {
 
 	// TODO: track seen tree ids, load trees that aren't in the set
 	for _, id := range snapshots {
-		// try to load snapshot blobs from cache
-		rd, err := arch.c.Load(backend.Snapshot, "blobs", id)
+		m, err := arch.c.LoadMap(arch.s, id)
 		if err != nil {
 			debug.Log("Archiver.Preload", "blobs for snapshot %v not cached: %v", id.Str(), err)
-			return err
-		}
 
-		debug.Log("Archiver.Preload", "load cached blobs for snapshot %v", id.Str())
-		dec := json.NewDecoder(rd)
-
-		m := &Map{}
-		err = dec.Decode(m)
-		if err != nil {
-			debug.Log("Archiver.Preload", "error loading cached blobs for snapshot %v: %v", id.Str(), err)
-			continue
+			// build new cache
+			m, err = CacheSnapshotBlobs(arch.s, arch.c, id)
+			if err != nil {
+				debug.Log("Archiver.Preload", "unable to cache snapshot blobs for %v: %v", id.Str(), err)
+				return err
+			}
 		}
 
 		arch.m.Merge(m)
@@ -473,9 +468,9 @@ func (arch *Archiver) dirWorker(wg *sync.WaitGroup, p *Progress, done <-chan str
 					debug.Log("Archiver.dirWorker", "got tree node for %s: %v", node.path, node.blobs)
 				}
 
+				// also store blob in tree map
 				for _, blob := range node.blobs {
 					tree.Map.Insert(blob)
-					arch.m.Insert(blob)
 				}
 			}
 
@@ -761,11 +756,12 @@ func (arch *Archiver) Snapshot(p *Progress, paths []string, pid backend.ID) (*Sn
 
 	// receive the top-level tree
 	root := (<-resCh).(*Node)
-	debug.Log("Archiver.Snapshot", "root node received: %v", root.blobs[0])
-	sn.Tree = root.blobs[0]
+	blob := root.blobs[0]
+	debug.Log("Archiver.Snapshot", "root node received: %v", blob)
+	sn.Tree = blob
 
 	// save snapshot
-	blob, err := arch.s.SaveJSON(backend.Snapshot, sn)
+	blob, err = arch.s.SaveJSON(backend.Snapshot, sn)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -776,23 +772,13 @@ func (arch *Archiver) Snapshot(p *Progress, paths []string, pid backend.ID) (*Sn
 	debug.Log("Archiver.Snapshot", "saved snapshot %v", blob.Storage.Str())
 
 	// cache blobs
-	wr, err := arch.c.Store(backend.Snapshot, "blobs", blob.Storage)
+	err = arch.c.StoreMap(sn.id, arch.m)
 	if err != nil {
 		debug.Log("Archiver.Snapshot", "unable to cache blobs for snapshot %v: %v", blob.Storage.Str(), err)
 		fmt.Fprintf(os.Stderr, "unable to cache blobs for snapshot %v: %v\n", blob.Storage.Str(), err)
 		return sn, blob.Storage, nil
 	}
 
-	enc := json.NewEncoder(wr)
-	err = enc.Encode(arch.m)
-	if err != nil {
-		debug.Log("Archiver.Snapshot", "error encoding map for snapshot %v: %v", blob.Storage.Str(), err)
-	} else {
-		debug.Log("Archiver.Snapshot", "cached %d blobs for snapshot %v", arch.m.Len(), blob.Storage.Str())
-	}
-
-	wr.Close()
-
 	return sn, blob.Storage, nil
 }
 

cache.go

@@ -1,11 +1,13 @@
 package restic
 
 import (
+	"encoding/json"
 	"fmt"
 	"io"
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"github.com/restic/restic/backend"
 	"github.com/restic/restic/debug"
@@ -203,3 +205,80 @@ func (c *Cache) filename(t backend.Type, subtype string, id backend.ID) (string,
 
 	return "", fmt.Errorf("cache not supported for type %v", t)
 }
+
+// high-level functions
+
+// CacheSnapshotBlobs creates a cache of all the blobs used within the
+// snapshot. It collects all blobs from all trees and saves the resulting map
+// to the cache and returns the map.
+func CacheSnapshotBlobs(s Server, c *Cache, id backend.ID) (*Map, error) {
+	debug.Log("CacheSnapshotBlobs", "create cache for snapshot %v", id.Str())
+
+	sn, err := LoadSnapshot(s, id)
+	if err != nil {
+		debug.Log("CacheSnapshotBlobs", "unable to load snapshot %v: %v", id.Str(), err)
+		return nil, err
+	}
+
+	m := NewMap()
+
+	// add top-level node
+	m.Insert(sn.Tree)
+
+	// start walker
+	var wg sync.WaitGroup
+	ch := make(chan WalkTreeJob)
+
+	wg.Add(1)
+	go func() {
+		WalkTree(s, sn.Tree.Storage, nil, ch)
+		wg.Done()
+	}()
+
+	for i := 0; i < maxConcurrencyPreload; i++ {
+		wg.Add(1)
+		go func() {
+			for job := range ch {
+				if job.Tree == nil {
+					continue
+				}
+				debug.Log("CacheSnapshotBlobs", "got job %v", job)
+				m.Merge(job.Tree.Map)
+			}
+
+			wg.Done()
+		}()
+	}
+
+	wg.Wait()
+
+	// save blob list for snapshot
+	return m, c.StoreMap(id, m)
+}
+
+func (c *Cache) StoreMap(snid backend.ID, m *Map) error {
+	wr, err := c.Store(backend.Snapshot, "blobs", snid)
+	if err != nil {
+		return nil
+	}
+	defer wr.Close()
+
+	enc := json.NewEncoder(wr)
+	err = enc.Encode(m)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *Cache) LoadMap(s Server, snid backend.ID) (*Map, error) {
+	rd, err := c.Load(backend.Snapshot, "blobs", snid)
+	if err != nil {
+		return nil, err
+	}
+
+	m := &Map{}
+	err = json.NewDecoder(rd).Decode(m)
+	return m, err
+}

cache_test.go

@@ -0,0 +1,45 @@
+package restic_test
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/restic/restic"
+	"github.com/restic/restic/backend"
+)
+
+func TestCache(t *testing.T) {
+	be := setupBackend(t)
+	defer teardownBackend(t, be)
+	key := setupKey(t, be, "geheim")
+	server := restic.NewServerWithKey(be, key)
+
+	cache, err := restic.NewCache(server)
+	ok(t, err)
+
+	arch, err := restic.NewArchiver(server)
+	ok(t, err)
+
+	// archive some files, this should automatically cache all blobs from the snapshot
+	_, id, err := arch.Snapshot(nil, []string{*benchArchiveDirectory}, nil)
+
+	// try to load map from cache
+	rd, err := cache.Load(backend.Snapshot, "blobs", id)
+	ok(t, err)
+
+	dec := json.NewDecoder(rd)
+
+	m := &restic.Map{}
+	err = dec.Decode(m)
+	ok(t, err)
+
+	// remove cached blob list
+	ok(t, cache.Purge(backend.Snapshot, "blobs", id))
+
+	// recreate cached blob list
+	m2, err := restic.CacheSnapshotBlobs(server, cache, id)
+	ok(t, err)
+
+	// compare maps
+	assert(t, m.Equals(m2), "Maps are not equal")
+}

map.go

@@ -124,15 +124,25 @@ func (bl *Map) StorageIDs() []backend.ID {
 }
 
 func (bl *Map) Equals(other *Map) bool {
+	if bl == nil && other == nil {
+		return true
+	}
+
+	if bl == nil || other == nil {
+		return false
+	}
+
 	bl.m.Lock()
 	defer bl.m.Unlock()
 
 	if len(bl.list) != len(other.list) {
+		debug.Log("Map.Equals", "length does not match: %d != %d", len(bl.list), len(other.list))
 		return false
 	}
 
 	for i := 0; i < len(bl.list); i++ {
 		if bl.list[i].Compare(other.list[i]) != 0 {
+			debug.Log("Map.Equals", "entry %d does not match: %v != %v", i, bl.list[i], other.list[i])
 			return false
 		}
 	}