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Cleanup storage cache metrics

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Split request and hit metrics into separate metrics, rather than using
labels. This avoids duplication of data and makes metric math easier.

* Count cache errors separately to avoid weird math.
* Hit ratio: `registry_storage_cache_hits_total / registry_storage_cache_requests_total`
* Miss ratio: `1 - (registry_storage_cache_hits_total / registry_storage_cache_requests_total`
* Misses: `registry_storage_cache_requests_total -
registry_storage_cache_hits_total`

Signed-off-by: Ben Kochie <superq@gmail.com>
This commit is contained in:
Ben Kochie 2019-04-09 13:43:55 +02:00 committed by SuperQ
parent 807a836852
commit c19adfdf06
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GPG key ID: C646B23C9E3245F1
1 changed files with 11 additions and 7 deletions
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18
registry/storage/cache/cachedblobdescriptorstore.go vendored
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@ -14,8 +14,14 @@ type cachedBlobStatter struct {
backend distribution.BlobDescriptorService
}
// cacheCount is the number of total cache request received/hits/misses
var cacheCount = prometheus.StorageNamespace.NewLabeledCounter("cache", "The number of cache request received", "type")
var (
// cacheRequestCount is the number of total cache requests received.
cacheRequestCount = prometheus.StorageNamespace.NewCounter("cache_requests", "The number of cache request received")
// cacheRequestCount is the number of total cache requests received.
cacheHitCount = prometheus.StorageNamespace.NewCounter("cache_hits", "The number of cache request received")
// cacheErrorCount is the number of cache request errors.
cacheErrorCount = prometheus.StorageNamespace.NewCounter("cache_errors", "The number of cache request errors")
)
// NewCachedBlobStatter creates a new statter which prefers a cache and
// falls back to a backend.
@ -27,12 +33,12 @@ func NewCachedBlobStatter(cache distribution.BlobDescriptorService, backend dist
}
func (cbds *cachedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
cacheCount.WithValues("Request").Inc(1)
cacheRequestCount.Inc(1)
// try getting from cache
desc, cacheErr := cbds.cache.Stat(ctx, dgst)
if cacheErr == nil {
cacheCount.WithValues("Hit").Inc(1)
cacheHitCount.Inc(1)
return desc, nil
}
@ -43,8 +49,6 @@ func (cbds *cachedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (di
}
if cacheErr == distribution.ErrBlobUnknown {
// cache doesn't have info. update it with info got from backend
cacheCount.WithValues("Miss").Inc(1)
if err := cbds.cache.SetDescriptor(ctx, dgst, desc); err != nil {
dcontext.GetLoggerWithField(ctx, "blob", dgst).WithError(err).Error("error from cache setting desc")
}
@ -52,7 +56,7 @@ func (cbds *cachedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (di
} else {
// unknown error from cache. just log and error. do not store cache as it may be trigger many set calls
dcontext.GetLoggerWithField(ctx, "blob", dgst).WithError(cacheErr).Error("error from cache stat(ing) blob")
cacheCount.WithValues("Error").Inc(1)
cacheErrorCount.Inc(1)
}
return desc, nil