// 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/server/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 GCS-bucket cache.
func manifestFromCache(ctx context.Context, s *State, key string) (json.RawMessage, bool) {
if m, cached := s.Cache.manifestFromLocalCache(key); cached {
return m, true
}
obj := s.Bucket.Object("manifests/" + key)
// Probe whether the file exists before trying to fetch it.
_, err := obj.Attrs(ctx)
if err != nil {
return nil, false
}
r, err := obj.NewReader(ctx)
if err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to retrieve manifest from bucket cache")
return nil, false
}
defer r.Close()
m, err := ioutil.ReadAll(r)
if err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to read cached manifest from bucket")
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)
obj := s.Bucket.Object("manifests/" + key)
w := obj.NewWriter(ctx)
r := bytes.NewReader([]byte(m))
size, err := io.Copy(w, r)
if err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to cache manifest to GCS")
return
}
if err = w.Close(); err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to cache manifest to GCS")
return
}
log.WithFields(log.Fields{
"manifest": key,
"size": size,
}).Info("cached manifest to GCS")
}
// 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
}
obj := s.Bucket.Object("builds/" + key)
_, err := obj.Attrs(ctx)
if err != nil {
return nil, false
}
r, err := obj.NewReader(ctx)
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to retrieve cached layer from GCS")
return nil, false
}
defer r.Close()
jb := bytes.NewBuffer([]byte{})
_, err = io.Copy(jb, r)
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to read cached layer from GCS")
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)
obj := s.Bucket.Object("builds/" + key)
j, _ := json.Marshal(&entry)
w := obj.NewWriter(ctx)
_, err := io.Copy(w, bytes.NewReader(j))
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to cache layer")
return
}
if err = w.Close(); err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to cache layer")
return
}
}
