82 lines
2.5 KiB
Go
82 lines
2.5 KiB
Go
package cache
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import (
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"context"
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"github.com/distribution/distribution/v3"
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dcontext "github.com/distribution/distribution/v3/context"
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prometheus "github.com/distribution/distribution/v3/metrics"
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"github.com/opencontainers/go-digest"
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)
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type cachedBlobStatter struct {
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cache distribution.BlobDescriptorService
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backend distribution.BlobDescriptorService
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}
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var (
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// cacheCount is the number of total cache request received/hits/misses
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cacheCount = prometheus.StorageNamespace.NewLabeledCounter("cache", "The number of cache request received", "type")
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)
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// NewCachedBlobStatter creates a new statter which prefers a cache and
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// falls back to a backend.
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func NewCachedBlobStatter(cache distribution.BlobDescriptorService, backend distribution.BlobDescriptorService) distribution.BlobDescriptorService {
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return &cachedBlobStatter{
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cache: cache,
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backend: backend,
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}
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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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cacheCount.WithValues("Request").Inc(1)
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// try getting from cache
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desc, cacheErr := cbds.cache.Stat(ctx, dgst)
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if cacheErr == nil {
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cacheCount.WithValues("Hit").Inc(1)
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return desc, nil
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}
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// couldn't get from cache; get from backend
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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 cacheErr == distribution.ErrBlobUnknown {
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// cache doesn't have info. update it with info got from backend
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cacheCount.WithValues("Miss").Inc(1)
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if err := cbds.cache.SetDescriptor(ctx, dgst, desc); err != nil {
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dcontext.GetLoggerWithField(ctx, "blob", dgst).WithError(err).Error("error from cache setting desc")
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}
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// we don't need to return cache error upstream if any. continue returning value from backend
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} else {
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// unknown error from cache. just log and error. do not store cache as it may be trigger many set calls
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dcontext.GetLoggerWithField(ctx, "blob", dgst).WithError(cacheErr).Error("error from cache stat(ing) blob")
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cacheCount.WithValues("Error").Inc(1)
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}
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return desc, nil
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}
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func (cbds *cachedBlobStatter) Clear(ctx context.Context, dgst digest.Digest) error {
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err := cbds.cache.Clear(ctx, dgst)
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if err != nil {
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return err
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}
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err = cbds.backend.Clear(ctx, dgst)
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if err != nil {
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return err
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}
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return nil
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}
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func (cbds *cachedBlobStatter) SetDescriptor(ctx context.Context, dgst digest.Digest, desc distribution.Descriptor) error {
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if err := cbds.cache.SetDescriptor(ctx, dgst, desc); err != nil {
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dcontext.GetLoggerWithField(ctx, "blob", dgst).WithError(err).Error("error from cache setting desc")
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}
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return nil
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}
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