1 files changed, 236 insertions, 0 deletions
diff --git a/tools/nixery/builder/cache.go b/tools/nixery/builder/cache.go
new file mode 100644
index 000000000000..a4ebe03e1c94
--- /dev/null
+++ b/tools/nixery/builder/cache.go
@@ -0,0 +1,236 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+package builder
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"io"
+	"io/ioutil"
+	"os"
+	"sync"
+
+	"github.com/google/nixery/manifest"
+	log "github.com/sirupsen/logrus"
+)
+
+// LocalCache implements the structure used for local caching of
+// manifests and layer uploads.
+type LocalCache struct {
+	// Manifest cache
+	mmtx sync.RWMutex
+	mdir string
+
+	// Layer cache
+	lmtx   sync.RWMutex
+	lcache map[string]manifest.Entry
+}
+
+// Creates an in-memory cache and ensures that the local file path for
+// manifest caching exists.
+func NewCache() (LocalCache, error) {
+	path := os.TempDir() + "/nixery"
+	err := os.MkdirAll(path, 0755)
+	if err != nil {
+		return LocalCache{}, err
+	}
+
+	return LocalCache{
+		mdir:   path + "/",
+		lcache: make(map[string]manifest.Entry),
+	}, nil
+}
+
+// Retrieve a cached manifest if the build is cacheable and it exists.
+func (c *LocalCache) manifestFromLocalCache(key string) (json.RawMessage, bool) {
+	c.mmtx.RLock()
+	defer c.mmtx.RUnlock()
+
+	f, err := os.Open(c.mdir + key)
+	if err != nil {
+		// This is a debug log statement because failure to
+		// read the manifest key is currently expected if it
+		// is not cached.
+		log.WithError(err).WithField("manifest", key).
+			Debug("failed to read manifest from local cache")
+
+		return nil, false
+	}
+	defer f.Close()
+
+	m, err := ioutil.ReadAll(f)
+	if err != nil {
+		log.WithError(err).WithField("manifest", key).
+			Error("failed to read manifest from local cache")
+
+		return nil, false
+	}
+
+	return json.RawMessage(m), true
+}
+
+// Adds the result of a manifest build to the local cache, if the
+// manifest is considered cacheable.
+//
+// Manifests can be quite large and are cached on disk instead of in
+// memory.
+func (c *LocalCache) localCacheManifest(key string, m json.RawMessage) {
+	c.mmtx.Lock()
+	defer c.mmtx.Unlock()
+
+	err := ioutil.WriteFile(c.mdir+key, []byte(m), 0644)
+	if err != nil {
+		log.WithError(err).WithField("manifest", key).
+			Error("failed to locally cache manifest")
+	}
+}
+
+// Retrieve a layer build from the local cache.
+func (c *LocalCache) layerFromLocalCache(key string) (*manifest.Entry, bool) {
+	c.lmtx.RLock()
+	e, ok := c.lcache[key]
+	c.lmtx.RUnlock()
+
+	return &e, ok
+}
+
+// Add a layer build result to the local cache.
+func (c *LocalCache) localCacheLayer(key string, e manifest.Entry) {
+	c.lmtx.Lock()
+	c.lcache[key] = e
+	c.lmtx.Unlock()
+}
+
+// Retrieve a manifest from the cache(s). First the local cache is
+// checked, then the storage backend.
+func manifestFromCache(ctx context.Context, s *State, key string) (json.RawMessage, bool) {
+	if m, cached := s.Cache.manifestFromLocalCache(key); cached {
+		return m, true
+	}
+
+	r, err := s.Storage.Fetch(ctx, "manifests/"+key)
+	if err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"manifest": key,
+			"backend":  s.Storage.Name(),
+		}).Error("failed to fetch manifest from cache")
+
+		return nil, false
+	}
+	defer r.Close()
+
+	m, err := ioutil.ReadAll(r)
+	if err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"manifest": key,
+			"backend":  s.Storage.Name(),
+		}).Error("failed to read cached manifest from storage backend")
+
+		return nil, false
+	}
+
+	go s.Cache.localCacheManifest(key, m)
+	log.WithField("manifest", key).Info("retrieved manifest from GCS")
+
+	return json.RawMessage(m), true
+}
+
+// Add a manifest to the bucket & local caches
+func cacheManifest(ctx context.Context, s *State, key string, m json.RawMessage) {
+	go s.Cache.localCacheManifest(key, m)
+
+	path := "manifests/" + key
+	_, size, err := s.Storage.Persist(ctx, path, func(w io.Writer) (string, int64, error) {
+		size, err := io.Copy(w, bytes.NewReader([]byte(m)))
+		return "", size, err
+	})
+
+	if err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"manifest": key,
+			"backend":  s.Storage.Name(),
+		}).Error("failed to cache manifest to storage backend")
+
+		return
+	}
+
+	log.WithFields(log.Fields{
+		"manifest": key,
+		"size":     size,
+		"backend":  s.Storage.Name(),
+	}).Info("cached manifest to storage backend")
+}
+
+// Retrieve a layer build from the cache, first checking the local
+// cache followed by the bucket cache.
+func layerFromCache(ctx context.Context, s *State, key string) (*manifest.Entry, bool) {
+	if entry, cached := s.Cache.layerFromLocalCache(key); cached {
+		return entry, true
+	}
+
+	r, err := s.Storage.Fetch(ctx, "builds/"+key)
+	if err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"layer":   key,
+			"backend": s.Storage.Name(),
+		}).Debug("failed to retrieve cached layer from storage backend")
+
+		return nil, false
+	}
+	defer r.Close()
+
+	jb := bytes.NewBuffer([]byte{})
+	_, err = io.Copy(jb, r)
+	if err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"layer":   key,
+			"backend": s.Storage.Name(),
+		}).Error("failed to read cached layer from storage backend")
+
+		return nil, false
+	}
+
+	var entry manifest.Entry
+	err = json.Unmarshal(jb.Bytes(), &entry)
+	if err != nil {
+		log.WithError(err).WithField("layer", key).
+			Error("failed to unmarshal cached layer")
+
+		return nil, false
+	}
+
+	go s.Cache.localCacheLayer(key, entry)
+	return &entry, true
+}
+
+func cacheLayer(ctx context.Context, s *State, key string, entry manifest.Entry) {
+	s.Cache.localCacheLayer(key, entry)
+
+	j, _ := json.Marshal(&entry)
+	path := "builds/" + key
+	_, _, err := s.Storage.Persist(ctx, path, func(w io.Writer) (string, int64, error) {
+		size, err := io.Copy(w, bytes.NewReader(j))
+		return "", size, err
+	})
+
+	if err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"layer":   key,
+			"backend": s.Storage.Name(),
+		}).Error("failed to cache layer")
+	}
+
+	return
+}