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// 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 (
"sync"
"time"
)
// recencyThreshold is the amount of time that a manifest build will be cached
// for. When using the channel mechanism for retrieving nixpkgs, Nix will
// occasionally re-fetch the channel so things can in fact change while the
// instance is running.
const recencyThreshold = time.Duration(6) * time.Hour
type manifestEntry struct {
built time.Time
path string
}
type void struct{}
type BuildCache struct {
mmtx sync.RWMutex
mcache map[string]manifestEntry
lmtx sync.RWMutex
lcache map[string]void
}
func NewCache() BuildCache {
return BuildCache{
mcache: make(map[string]manifestEntry),
lcache: make(map[string]void),
}
}
// 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 *BuildCache) 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 *BuildCache) sawLayer(hash string) {
c.lmtx.Lock()
defer c.lmtx.Unlock()
c.lcache[hash] = void{}
}
// Has this manifest been built already? If yes, we can reuse the
// result given that the build happened recently enough.
func (c *BuildCache) manifestFromCache(image *Image) (string, bool) {
c.mmtx.RLock()
entry, ok := c.mcache[image.Name+image.Tag]
c.mmtx.RUnlock()
if !ok {
return "", false
}
if time.Since(entry.built) > recencyThreshold {
return "", false
}
return entry.path, true
}
// Adds the result of a manifest build to the cache.
func (c *BuildCache) cacheManifest(image *Image, path string) {
entry := manifestEntry{
built: time.Now(),
path: path,
}
c.mmtx.Lock()
c.mcache[image.Name+image.Tag] = entry
c.mmtx.Unlock()
}
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