// 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"
"log"
"os"
"sync"
"cloud.google.com/go/storage"
)
type void struct{}
type Build struct {
SHA256 string `json:"sha256"`
MD5 string `json:"md5"`
}
// LocalCache implements the structure used for local caching of
// manifests and layer uploads.
type LocalCache struct {
// Manifest cache
mmtx sync.RWMutex
mcache map[string]string
// Layer (tarball) cache
lmtx sync.RWMutex
lcache map[string]void
// Layer (build) cache
bmtx sync.RWMutex
bcache map[string]Build
}
func NewCache() LocalCache {
return LocalCache{
mcache: make(map[string]string),
lcache: make(map[string]void),
bcache: make(map[string]Build),
}
}
// Has this layer hash already been seen by this Nixery instance? If
// yes, we can skip upload checking and such because it has already
// been done.
func (c *LocalCache) hasSeenLayer(hash string) bool {
c.lmtx.RLock()
defer c.lmtx.RUnlock()
_, seen := c.lcache[hash]
return seen
}
// Layer has now been seen and should be stored.
func (c *LocalCache) sawLayer(hash string) {
c.lmtx.Lock()
defer c.lmtx.Unlock()
c.lcache[hash] = void{}
}
// Retrieve a cached manifest if the build is cacheable and it exists.
func (c *LocalCache) manifestFromLocalCache(key string) (string, bool) {
c.mmtx.RLock()
path, ok := c.mcache[key]
c.mmtx.RUnlock()
if !ok {
return "", false
}
return path, true
}
// Adds the result of a manifest build to the local cache, if the
// manifest is considered cacheable.
func (c *LocalCache) localCacheManifest(key, path string) {
c.mmtx.Lock()
c.mcache[key] = path
c.mmtx.Unlock()
}
// Retrieve a cached build from the local cache.
func (c *LocalCache) buildFromLocalCache(key string) (*Build, bool) {
c.bmtx.RLock()
b, ok := c.bcache[key]
c.bmtx.RUnlock()
return &b, ok
}
// Add a build result to the local cache.
func (c *LocalCache) localCacheBuild(key string, b Build) {
c.bmtx.Lock()
c.bcache[key] = b
c.bmtx.Unlock()
}
// Retrieve a manifest from the cache(s). First the local cache is
// checked, then the GCS-bucket cache.
func manifestFromCache(ctx context.Context, cache *LocalCache, bucket *storage.BucketHandle, key string) (string, bool) {
path, cached := cache.manifestFromLocalCache(key)
if cached {
return path, true
}
obj := bucket.Object("manifests/" + key)
// Probe whether the file exists before trying to fetch it.
_, err := obj.Attrs(ctx)
if err != nil {
return "", false
}
r, err := obj.NewReader(ctx)
if err != nil {
log.Printf("Failed to retrieve manifest '%s' from cache: %s\n", key, err)
return "", false
}
defer r.Close()
path = os.TempDir() + "/" + key
f, _ := os.Create(path)
defer f.Close()
_, err = io.Copy(f, r)
if err != nil {
log.Printf("Failed to read cached manifest for '%s': %s\n", key, err)
}
log.Printf("Retrieved manifest for sha1:%s from GCS\n", key)
cache.localCacheManifest(key, path)
return path, true
}
// Add a manifest to the bucket & local caches
func cacheManifest(ctx *context.Context, cache *LocalCache, bucket *storage.BucketHandle, key, path string) {
cache.localCacheManifest(key, path)
obj := bucket.Object("manifests/" + key)
w := obj.NewWriter(*ctx)
f, err := os.Open(path)
if err != nil {
log.Printf("failed to open manifest sha1:%s for cache upload: %s\n", key, err)
return
}
defer f.Close()
size, err := io.Copy(w, f)
if err != nil {
log.Printf("failed to cache manifest sha1:%s: %s\n", key, err)
return
}
if err = w.Close(); err != nil {
log.Printf("failed to cache manifest sha1:%s: %s\n", key, err)
return
}
log.Printf("Cached manifest sha1:%s (%v bytes written)\n", key, size)
}
// Retrieve a build from the cache, first checking the local cache
// followed by the bucket cache.
func buildFromCache(ctx *context.Context, cache *LocalCache, bucket *storage.BucketHandle, key string) (*Build, bool) {
build, cached := cache.buildFromLocalCache(key)
if cached {
return build, true
}
obj := bucket.Object("builds/" + key)
_, err := obj.Attrs(*ctx)
if err != nil {
return nil, false
}
r, err := obj.NewReader(*ctx)
if err != nil {
log.Printf("Failed to retrieve build '%s' from cache: %s\n", key, err)
return nil, false
}
defer r.Close()
jb := bytes.NewBuffer([]byte{})
_, err = io.Copy(jb, r)
if err != nil {
log.Printf("Failed to read build '%s' from cache: %s\n", key, err)
return nil, false
}
var b Build
err = json.Unmarshal(jb.Bytes(), &build)
if err != nil {
log.Printf("Failed to unmarshal build '%s' from cache: %s\n", key, err)
return nil, false
}
return &b, true
}
func cacheBuild(ctx context.Context, cache *LocalCache, bucket *storage.BucketHandle, key string, build Build) {
cache.localCacheBuild(key, build)
obj := bucket.Object("builds/" + key)
j, _ := json.Marshal(&build)
w := obj.NewWriter(ctx)
_, err := io.Copy(w, bytes.NewReader(j))
if err != nil {
log.Printf("failed to cache build '%s': %s\n", key, err)
return
}
}
