package groupcache
import "github.com/golang/groupcache"
Package groupcache provides a data loading mechanism with caching and de-duplication that works across a set of peer processes.
Each data Get first consults its local cache, otherwise delegates to the requested key's canonical owner, which then checks its cache or finally gets the data. In the common case, many concurrent cache misses across a set of peers for the same key result in just one cache fill.
Index ¶
- func RegisterNewGroupHook(fn func(*Group))
- func RegisterPeerPicker(fn func() PeerPicker)
- func RegisterPerGroupPeerPicker(fn func(groupName string) PeerPicker)
- func RegisterServerStart(fn func())
- type AtomicInt
- func (i *AtomicInt) Add(n int64)
- func (i *AtomicInt) Get() int64
- func (i *AtomicInt) String() string
- type ByteView
- func (v ByteView) At(i int) byte
- func (v ByteView) ByteSlice() []byte
- func (v ByteView) Copy(dest []byte) int
- func (v ByteView) Equal(b2 ByteView) bool
- func (v ByteView) EqualBytes(b2 []byte) bool
- func (v ByteView) EqualString(s string) bool
- func (v ByteView) Len() int
- func (v ByteView) ReadAt(p []byte, off int64) (n int, err error)
- func (v ByteView) Reader() io.ReadSeeker
- func (v ByteView) Slice(from, to int) ByteView
- func (v ByteView) SliceFrom(from int) ByteView
- func (v ByteView) String() string
- func (v ByteView) WriteTo(w io.Writer) (n int64, err error)
- type CacheStats
- type CacheType
- type Context
- type Getter
- type GetterFunc
- type Group
- func GetGroup(name string) *Group
- func NewGroup(name string, cacheBytes int64, getter Getter) *Group
- func (g *Group) CacheStats(which CacheType) CacheStats
- func (g *Group) Get(ctx context.Context, key string, dest Sink) error
- func (g *Group) Name() string
- type HTTPPool
- func NewHTTPPool(self string) *HTTPPool
- func NewHTTPPoolOpts(self string, o *HTTPPoolOptions) *HTTPPool
- func (p *HTTPPool) PickPeer(key string) (ProtoGetter, bool)
- func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request)
- func (p *HTTPPool) Set(peers ...string)
- type HTTPPoolOptions
- type NoPeers
- type PeerPicker
- type ProtoGetter
- type Sink
- func AllocatingByteSliceSink(dst *[]byte) Sink
- func ByteViewSink(dst *ByteView) Sink
- func ProtoSink(m proto.Message) Sink
- func StringSink(sp *string) Sink
- func TruncatingByteSliceSink(dst *[]byte) Sink
- type Stats
Functions ¶
func RegisterNewGroupHook ¶
func RegisterNewGroupHook(fn func(*Group))
RegisterNewGroupHook registers a hook that is run each time a group is created.
func RegisterPeerPicker ¶
func RegisterPeerPicker(fn func() PeerPicker)
RegisterPeerPicker registers the peer initialization function. It is called once, when the first group is created. Either RegisterPeerPicker or RegisterPerGroupPeerPicker should be called exactly once, but not both.
func RegisterPerGroupPeerPicker ¶
func RegisterPerGroupPeerPicker(fn func(groupName string) PeerPicker)
RegisterPerGroupPeerPicker registers the peer initialization function, which takes the groupName, to be used in choosing a PeerPicker. It is called once, when the first group is created. Either RegisterPeerPicker or RegisterPerGroupPeerPicker should be called exactly once, but not both.
func RegisterServerStart ¶
func RegisterServerStart(fn func())
RegisterServerStart registers a hook that is run when the first group is created.
Types ¶
type AtomicInt ¶
type AtomicInt int64
An AtomicInt is an int64 to be accessed atomically.
func (*AtomicInt) Add ¶
Add atomically adds n to i.
func (*AtomicInt) Get ¶
Get atomically gets the value of i.
func (*AtomicInt) String ¶
type ByteView ¶
type ByteView struct {
// contains filtered or unexported fields
}
A ByteView holds an immutable view of bytes. Internally it wraps either a []byte or a string, but that detail is invisible to callers.
A ByteView is meant to be used as a value type, not a pointer (like a time.Time).
func (ByteView) At ¶
At returns the byte at index i.
func (ByteView) ByteSlice ¶
ByteSlice returns a copy of the data as a byte slice.
func (ByteView) Copy ¶
Copy copies b into dest and returns the number of bytes copied.
func (ByteView) Equal ¶
Equal returns whether the bytes in b are the same as the bytes in b2.
func (ByteView) EqualBytes ¶
EqualBytes returns whether the bytes in b are the same as the bytes in b2.
func (ByteView) EqualString ¶
EqualString returns whether the bytes in b are the same as the bytes in s.
func (ByteView) Len ¶
Len returns the view's length.
func (ByteView) ReadAt ¶
ReadAt implements io.ReaderAt on the bytes in v.
func (ByteView) Reader ¶
func (v ByteView) Reader() io.ReadSeeker
Reader returns an io.ReadSeeker for the bytes in v.
func (ByteView) Slice ¶
Slice slices the view between the provided from and to indices.
func (ByteView) SliceFrom ¶
SliceFrom slices the view from the provided index until the end.
func (ByteView) String ¶
String returns the data as a string, making a copy if necessary.
func (ByteView) WriteTo ¶
WriteTo implements io.WriterTo on the bytes in v.
type CacheStats ¶
CacheStats are returned by stats accessors on Group.
type CacheType ¶
type CacheType int
CacheType represents a type of cache.
const ( // The MainCache is the cache for items that this peer is the // owner for. MainCache CacheType = iota + 1 // The HotCache is the cache for items that seem popular // enough to replicate to this node, even though it's not the // owner. HotCache )
type Context ¶
Context is an alias to context.Context for backwards compatibility purposes.
type Getter ¶
type Getter interface {
// Get returns the value identified by key, populating dest.
//
// The returned data must be unversioned. That is, key must
// uniquely describe the loaded data, without an implicit
// current time, and without relying on cache expiration
// mechanisms.
Get(ctx context.Context, key string, dest Sink) error
}
A Getter loads data for a key.
type GetterFunc ¶
A GetterFunc implements Getter with a function.
func (GetterFunc) Get ¶
type Group ¶
type Group struct {
// Stats are statistics on the group.
Stats Stats
// contains filtered or unexported fields
}
A Group is a cache namespace and associated data loaded spread over a group of 1 or more machines.
func GetGroup ¶
GetGroup returns the named group previously created with NewGroup, or nil if there's no such group.
func NewGroup ¶
NewGroup creates a coordinated group-aware Getter from a Getter.
The returned Getter tries (but does not guarantee) to run only one Get call at once for a given key across an entire set of peer processes. Concurrent callers both in the local process and in other processes receive copies of the answer once the original Get completes.
The group name must be unique for each getter.
func (*Group) CacheStats ¶
func (g *Group) CacheStats(which CacheType) CacheStats
CacheStats returns stats about the provided cache within the group.
func (*Group) Get ¶
func (*Group) Name ¶
Name returns the name of the group.
type HTTPPool ¶
type HTTPPool struct {
// Context optionally specifies a context for the server to use when it
// receives a request.
// If nil, the server uses the request's context
Context func(*http.Request) context.Context
// Transport optionally specifies an http.RoundTripper for the client
// to use when it makes a request.
// If nil, the client uses http.DefaultTransport.
Transport func(context.Context) http.RoundTripper
// contains filtered or unexported fields
}
HTTPPool implements PeerPicker for a pool of HTTP peers.
func NewHTTPPool ¶
NewHTTPPool initializes an HTTP pool of peers, and registers itself as a PeerPicker. For convenience, it also registers itself as an http.Handler with http.DefaultServeMux. The self argument should be a valid base URL that points to the current server, for example "http://example.net:8000".
func NewHTTPPoolOpts ¶
func NewHTTPPoolOpts(self string, o *HTTPPoolOptions) *HTTPPool
NewHTTPPoolOpts initializes an HTTP pool of peers with the given options. Unlike NewHTTPPool, this function does not register the created pool as an HTTP handler. The returned *HTTPPool implements http.Handler and must be registered using http.Handle.
func (*HTTPPool) PickPeer ¶
func (p *HTTPPool) PickPeer(key string) (ProtoGetter, bool)
func (*HTTPPool) ServeHTTP ¶
func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request)
func (*HTTPPool) Set ¶
Set updates the pool's list of peers. Each peer value should be a valid base URL, for example "http://example.net:8000".
type HTTPPoolOptions ¶
type HTTPPoolOptions struct {
// BasePath specifies the HTTP path that will serve groupcache requests.
// If blank, it defaults to "/_groupcache/".
BasePath string
// Replicas specifies the number of key replicas on the consistent hash.
// If blank, it defaults to 50.
Replicas int
// HashFn specifies the hash function of the consistent hash.
// If blank, it defaults to crc32.ChecksumIEEE.
HashFn consistenthash.Hash
}
HTTPPoolOptions are the configurations of a HTTPPool.
type NoPeers ¶
type NoPeers struct{}
NoPeers is an implementation of PeerPicker that never finds a peer.
func (NoPeers) PickPeer ¶
func (NoPeers) PickPeer(key string) (peer ProtoGetter, ok bool)
type PeerPicker ¶
type PeerPicker interface {
// PickPeer returns the peer that owns the specific key
// and true to indicate that a remote peer was nominated.
// It returns nil, false if the key owner is the current peer.
PickPeer(key string) (peer ProtoGetter, ok bool)
}
PeerPicker is the interface that must be implemented to locate the peer that owns a specific key.
type ProtoGetter ¶
type ProtoGetter interface {
Get(ctx context.Context, in *pb.GetRequest, out *pb.GetResponse) error
}
ProtoGetter is the interface that must be implemented by a peer.
type Sink ¶
type Sink interface {
// SetString sets the value to s.
SetString(s string) error
// SetBytes sets the value to the contents of v.
// The caller retains ownership of v.
SetBytes(v []byte) error
// SetProto sets the value to the encoded version of m.
// The caller retains ownership of m.
SetProto(m proto.Message) error
// contains filtered or unexported methods
}
A Sink receives data from a Get call.
Implementation of Getter must call exactly one of the Set methods on success.
func AllocatingByteSliceSink ¶
AllocatingByteSliceSink returns a Sink that allocates a byte slice to hold the received value and assigns it to *dst. The memory is not retained by groupcache.
func ByteViewSink ¶
ByteViewSink returns a Sink that populates a ByteView.
func ProtoSink ¶
ProtoSink returns a sink that unmarshals binary proto values into m.
func StringSink ¶
StringSink returns a Sink that populates the provided string pointer.
func TruncatingByteSliceSink ¶
TruncatingByteSliceSink returns a Sink that writes up to len(*dst) bytes to *dst. If more bytes are available, they're silently truncated. If fewer bytes are available than len(*dst), *dst is shrunk to fit the number of bytes available.
type Stats ¶
type Stats struct {
Gets AtomicInt // any Get request, including from peers
CacheHits AtomicInt // either cache was good
PeerLoads AtomicInt // either remote load or remote cache hit (not an error)
PeerErrors AtomicInt
Loads AtomicInt // (gets - cacheHits)
LoadsDeduped AtomicInt // after singleflight
LocalLoads AtomicInt // total good local loads
LocalLoadErrs AtomicInt // total bad local loads
ServerRequests AtomicInt // gets that came over the network from peers
}
Stats are per-group statistics.
Source Files ¶
byteview.go groupcache.go http.go peers.go sinks.go
Directories ¶
| Path | Synopsis |
|---|---|
| consistenthash | Package consistenthash provides an implementation of a ring hash. |
| groupcachepb | |
| lru | Package lru implements an LRU cache. |
| singleflight | Package singleflight provides a duplicate function call suppression mechanism. |
| testpb |
- Version
- v0.0.0-20241129210726-2c02b8208cf8 (latest)
- Published
- Nov 29, 2024
- Platform
- linux/amd64
- Imports
- 17 packages
- Last checked
- 1 month ago –
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