open-consul/agent/cache/entry.go

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package cache
import (
"time"
"golang.org/x/time/rate"
"github.com/hashicorp/consul/lib/ttlcache"
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)
// cacheEntry stores a single cache entry.
//
// Note that this isn't a very optimized structure currently. There are
// a lot of improvements that can be made here in the long term.
type cacheEntry struct {
// Fields pertaining to the actual value
Value interface{}
// State can be used to store info needed by the cache type but that should
// not be part of the result the client gets. For example the Connect Leaf
// type needs to store additional data about when it last attempted a renewal
// that is not part of the actual IssuedCert struct it returns. It's opaque to
// the Cache but allows types to store additional data that is coupled to the
// cache entry's lifetime and will be aged out by TTL etc.
State interface{}
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Error error
Index uint64
// Metadata that is used for internal accounting
Valid bool // True if the Value is set
GoroutineID uint64 // Nonzero if a fetch goroutine is running.
Waiter chan struct{} // Closed when this entry is invalidated
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// Expiry contains information about the expiration of this
// entry. This is a pointer as its shared as a value in the
// ExpiryHeap as well.
Expiry *ttlcache.Entry
// FetchedAt stores the time the cache entry was retrieved for determining
// it's age later.
FetchedAt time.Time
// RefreshLostContact stores the time background refresh failed. It gets reset
// to zero after a background fetch has returned successfully, or after a
// background request has be blocking for at least 5 seconds, which ever
// happens first.
RefreshLostContact time.Time
// FetchRateLimiter limits the rate at which fetch is called for this entry.
FetchRateLimiter *rate.Limiter
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}