Struct Group

groupcache.go:142–178

A Group is a cache namespace and associated data loaded spread over a group of 1 or more machines.

// A Group is a cache namespace and associated data loaded spread over
// a group of 1 or more machines.
type Group struct {
	name       string
	getter     Getter
	peersOnce  sync.Once
	peers      PeerPicker
	cacheBytes int64 // limit for sum of mainCache and hotCache size

	// mainCache is a cache of the keys for which this process
	// (amongst its peers) is authoritative. That is, this cache
	// contains keys which consistent hash on to this process's
	// peer number.
	mainCache cache

	// hotCache contains keys/values for which this peer is not
	// authoritative (otherwise they would be in mainCache), but
	// are popular enough to warrant mirroring in this process to
	// avoid going over the network to fetch from a peer.  Having
	// a hotCache avoids network hotspotting, where a peer's
	// network card could become the bottleneck on a popular key.
	// This cache is used sparingly to maximize the total number
	// of key/value pairs that can be stored globally.
	hotCache cache

	// loadGroup ensures that each key is only fetched once
	// (either locally or remotely), regardless of the number of
	// concurrent callers.
	loadGroup flightGroup

	_ int32 // force Stats to be 8-byte aligned on 32-bit platforms

	// Stats are statistics on the group.
	Stats Stats

	// rand is only non-nil when testing,
	// to get predictable results in TestPeers.
	rand *rand.Rand
}

// flightGroup is defined as an interface which flightgroup.Group
// satisfies.  We define this so that we may test with an alternate