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cache.go
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package cache
import (
"context"
"errors"
"fmt"
"io"
"net/http"
"path"
"strconv"
"sync"
"time"
"github.com/opencontainers/go-digest"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/containerd/containerd/remotes"
"github.com/solo-io/wasme/pkg/pull"
)
type Cache interface {
Add(ctx context.Context, image string) (digest.Digest, error)
Get(ctx context.Context, digest digest.Digest) (io.ReadCloser, error)
http.Handler
}
type CacheImpl struct {
Puller pull.Puller
Resolver remotes.Resolver
cacheState cacheState
}
type fetchableDescriptor struct {
ocispec.Descriptor
fetcher func(ctx context.Context) (io.ReadCloser, error) //remotes.Fetcher
}
type cacheState struct {
descriptors []fetchableDescriptor
descriptorsLock sync.RWMutex
}
func (c *cacheState) add(d fetchableDescriptor) {
if c.find(d.Digest) != nil {
// check existance for idempotency
// technically metadata can be different, but its fine for now.
return
}
c.descriptorsLock.Lock()
c.descriptors = append(c.descriptors, d)
c.descriptorsLock.Unlock()
}
func (c *cacheState) find(digest digest.Digest) *fetchableDescriptor {
c.descriptorsLock.RLock()
defer c.descriptorsLock.RUnlock()
for _, d := range c.descriptors {
if d.Digest == digest {
d := d
return &d
}
}
return nil
}
func (c *CacheImpl) Add(ctx context.Context, image string) (digest.Digest, error) {
desc, err := c.Puller.PullCodeDescriptor(ctx, image)
if err != nil {
return digest.Digest(""), err
}
fd := fetchableDescriptor{
Descriptor: desc,
fetcher: func(subctx context.Context) (io.ReadCloser, error) {
fetcher, err := c.Resolver.Fetcher(subctx, image)
if err != nil {
return nil, err
}
return fetcher.Fetch(subctx, desc)
},
}
c.cacheState.add(fd)
return desc.Digest, err
}
func (c *CacheImpl) Get(ctx context.Context, digest digest.Digest) (io.ReadCloser, error) {
desc := c.cacheState.find(digest)
if desc == nil {
return nil, errors.New("not found")
}
return desc.fetcher(ctx)
}
func (c *CacheImpl) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
// parse the url
ctx := r.Context()
_, file := path.Split(r.URL.Path)
desc := c.cacheState.find(digest.Digest("sha256:" + file))
if desc == nil {
http.NotFound(rw, r)
return
}
rc, err := desc.fetcher(ctx)
if err != nil {
http.NotFound(rw, r)
return
}
defer rc.Close()
rw.Header().Set("Content-Type", desc.MediaType)
rw.Header().Set("Etag", "\""+string(desc.Digest)+"\"")
if rs, ok := rc.(io.ReadSeeker); ok {
// content of digests never changes so set mod time to a constant
// don't use zero time because serve content doesn't use that.
modTime := time.Date(2000, time.January, 1, 0, 0, 0, 0, time.UTC)
http.ServeContent(rw, r, file, modTime, rs)
} else {
rw.Header().Add("Content-Length", strconv.Itoa(int(desc.Size)))
if r.Method != "HEAD" {
_, err = io.Copy(rw, rc)
if err != nil {
// TODO: use real log
fmt.Printf("error http %v\n", err)
}
}
}
}