86 lines
2.6 KiB
Go
86 lines
2.6 KiB
Go
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/*
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Copyright 2012 Google Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// peers.go defines how processes find and communicate with their peers.
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package groupcache
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import (
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pb "github.com/golang/groupcache/groupcachepb"
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)
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// Context is an opaque value passed through calls to the
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// ProtoGetter. It may be nil if your ProtoGetter implementation does
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// not require a context.
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type Context interface{}
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// ProtoGetter is the interface that must be implemented by a peer.
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type ProtoGetter interface {
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Get(context Context, in *pb.GetRequest, out *pb.GetResponse) error
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}
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// PeerPicker is the interface that must be implemented to locate
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// the peer that owns a specific key.
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type PeerPicker interface {
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// PickPeer returns the peer that owns the specific key
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// and true to indicate that a remote peer was nominated.
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// It returns nil, false if the key owner is the current peer.
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PickPeer(key string) (peer ProtoGetter, ok bool)
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}
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// NoPeers is an implementation of PeerPicker that never finds a peer.
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type NoPeers struct{}
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func (NoPeers) PickPeer(key string) (peer ProtoGetter, ok bool) { return }
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var (
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portPicker func(groupName string) PeerPicker
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)
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// RegisterPeerPicker registers the peer initialization function.
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// It is called once, when the first group is created.
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// Either RegisterPeerPicker or RegisterPerGroupPeerPicker should be
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// called exactly once, but not both.
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func RegisterPeerPicker(fn func() PeerPicker) {
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if portPicker != nil {
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panic("RegisterPeerPicker called more than once")
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}
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portPicker = func(_ string) PeerPicker { return fn() }
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}
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// RegisterPerGroupPeerPicker registers the peer initialization function,
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// which takes the groupName, to be used in choosing a PeerPicker.
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// It is called once, when the first group is created.
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// Either RegisterPeerPicker or RegisterPerGroupPeerPicker should be
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// called exactly once, but not both.
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func RegisterPerGroupPeerPicker(fn func(groupName string) PeerPicker) {
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if portPicker != nil {
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panic("RegisterPeerPicker called more than once")
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}
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portPicker = fn
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}
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func getPeers(groupName string) PeerPicker {
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if portPicker == nil {
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return NoPeers{}
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}
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pk := portPicker(groupName)
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if pk == nil {
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pk = NoPeers{}
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}
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return pk
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}
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