mirror of https://github.com/docker/docs.git
85 lines
2.2 KiB
Go
85 lines
2.2 KiB
Go
package storage
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import (
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"expvar"
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"sync/atomic"
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"github.com/docker/distribution/context"
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"github.com/docker/distribution/digest"
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"github.com/docker/distribution"
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)
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type cachedBlobStatter struct {
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cache distribution.BlobDescriptorService
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backend distribution.BlobStatter
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}
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func (cbds *cachedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
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atomic.AddUint64(&blobStatterCacheMetrics.Stat.Requests, 1)
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desc, err := cbds.cache.Stat(ctx, dgst)
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if err != nil {
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if err != distribution.ErrBlobUnknown {
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context.GetLogger(ctx).Errorf("error retrieving descriptor from cache: %v", err)
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}
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goto fallback
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}
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atomic.AddUint64(&blobStatterCacheMetrics.Stat.Hits, 1)
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return desc, nil
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fallback:
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atomic.AddUint64(&blobStatterCacheMetrics.Stat.Misses, 1)
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desc, err = cbds.backend.Stat(ctx, dgst)
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if err != nil {
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return desc, err
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}
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if err := cbds.cache.SetDescriptor(ctx, dgst, desc); err != nil {
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context.GetLogger(ctx).Errorf("error adding descriptor %v to cache: %v", desc.Digest, err)
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}
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return desc, err
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}
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// blobStatterCacheMetrics keeps track of cache metrics for blob descriptor
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// cache requests. Note this is kept globally and made available via expvar.
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// For more detailed metrics, its recommend to instrument a particular cache
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// implementation.
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var blobStatterCacheMetrics struct {
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// Stat tracks calls to the caches.
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Stat struct {
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Requests uint64
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Hits uint64
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Misses uint64
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}
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}
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func init() {
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registry := expvar.Get("registry")
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if registry == nil {
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registry = expvar.NewMap("registry")
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}
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cache := registry.(*expvar.Map).Get("cache")
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if cache == nil {
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cache = &expvar.Map{}
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cache.(*expvar.Map).Init()
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registry.(*expvar.Map).Set("cache", cache)
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}
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storage := cache.(*expvar.Map).Get("storage")
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if storage == nil {
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storage = &expvar.Map{}
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storage.(*expvar.Map).Init()
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cache.(*expvar.Map).Set("storage", storage)
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}
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storage.(*expvar.Map).Set("blobdescriptor", expvar.Func(func() interface{} {
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// no need for synchronous access: the increments are atomic and
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// during reading, we don't care if the data is up to date. The
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// numbers will always *eventually* be reported correctly.
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return blobStatterCacheMetrics
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}))
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}
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